Abstract

We report the correlation between inner morphology, size and whispering gallery mode (WGM) behavior in ZnO microspheres (MSs) grown by hydrothermal method. WGMs in different ZnO microspheres with diameters in the range of 2 - 6 μm were analyzed by a modified refractive index (MRI) scheme. We found that the size dependence of WGMs in our system is more complicated than others because of the appearance of porosity inside each sphere. Such features might account for the refractive index change and peak shift. Despite that, our MRI scheme can detect such complex features and reproduce universal relations between all important quantities of a microsphere WGM resonator.

© 2016 Optical Society of America

Corrections

3 August 2016: A correction was made to the author affiliations.

1. Introduction

ZnO has attracted much interest as an important technological material. Physically, it is well-known for its wide band gap (3.3 eV), large free-exciton binding energy (60 meV), and ability to emit a wide spectrum in visible range that originates from numerous extrinsic and intrinsic deep-level impurities and complexes [1–5]. Recently, ZnO-based micro resonator has been considered as a good candidate for ultraviolet (UV) micro laser. It is a result of a unique combination between stable emission layer and good optical confinement. Lasing properties of those resonators was first reported in [6] for Fabry-Perot cavity. After that, countless efforts have been devoted on WGM in ZnO micro resonator to improve the lasing performance (see [7] and reference therein).

Among different morphologies that support WGMs, microsphere (MS) is the simplest 3D resonator. In spite of this, its WGM behavior exhibits very complicated behavior and possesses extraordinary high Q values of 108 - 109 [8]. ZnO microsphere resonator would be a promising system for many photonic applications. However, there are very few studies till now because of limitation for preparing smooth surface, perfect spherical symmetry and high crystalline quality. Two major methods for obtaining ZnO MSs (with size up to 10μm) are laser ablation [9] and hydrothermal synthesis [10].

Those studies have revealed unique WGM properties in ZnO MS, such as photo-induced UV, white light lasing [11–13] and field-induced UV lasing [14]. In our previous work [10], ZnO MSs with sizes from 1.52 μm to 2.7 μm were successful synthesized by hydrothermal techniques. Those spheres show sharp WGM peaks in wavelengths of 400nm – 800nm, and significant redshift of the exciton emission peak (with Δε ~0.3 eV) from the ZnO bulk value (3.3 eV). After careful analysis, it was deduced that a change in refractive index of bulk ZnO, Δn needs to be introduced to explain the data [10]. Those unique behaviors could not be observed in ZnO MSs fabricated by laser ablation [9,11–14]. The current work is therefore devoted to explain such behaviors. Photoluminescence (PL) spectrum and SEM picture for single ZnO MS were investigated systematically. PL spectra of ZnO MSs of various sizes were collected. As a result, the correlation between Δε, Δn and inner morphology can be analyzed.

2. Experimental and theoretical analysis

2.1 Synthesis of ZnO microspheres

ZnO MSs were synthesized by hydrothermal techniques described in our previous work [10]. It was optimized for the surface smoothness, and the size of such MS strongly depends on the molar ratio between Zn(NO3)2.6H2O and sodium citrate in reactant solution [15,16]. In order to obtain larger size (up to 10 µm) and smooth surface, this ratio should be in the range of 2.6 to 2.9 in our case. The as-prepared samples were dropped to Si substrate and then annealed at 550 °C for 12 hours in the ambient atmosphere before characterization.

The size of ZnO MSs on a Si substrate is measured by a scanning electron microscope (SEM-Nano Nova). The WGM behavior in PL spectrum of ZnO microcavities of various sizes is observed using a Horiba Jobin Yvon HR-800 UV setup with a He-Cd laser source (325 nm line). X-ray photoelectron spectroscopy (XPS) analyses were carried out in a XPS spectrometer (ULVAC-PHI 5000 Versaprobe) with a monochromatic Al Kα X-ray source (1486.6 eV). More information about X-ray diffraction (XRD), Raman properties and composition can be found in [10].

2.2 Modified Refractive Index model

In order to investigate the WGM behavior in spherical micro resonator, we applied the scheme previously described in [10,17]. Our scheme was modified based on similar scheme proposed elsewhere [18], where another iteration of Newton-Rapshon scheme was added after implementing Sellmeier’s dispersion relation [19] in order to solve the characteristic equation [20]. The refractive index n, cavity radius R, angular momentum mode number l and complex roots of resonance position k were then calculated in a self-consistent way. Then, those values were redefined again after modifying the refractive index.

Such modifications would produce Δn = |ng,exp(λl) − ng,bulk(λl)| where ng,exp(λl), ng,bulk(λl) are experimental and calculated group indices, respectively. On the other hand, the assignment of angular momentum mode number l is made by optimizing the indicator function D (l, l’) [10].

As shown in previous studies, the modified refractive index (MRI) scheme worked well in evaluating the refractive index shift in hydrothermally-grown ZnO microcavities. However, this shift is negligible for MSs fabricated by laser ablation [9,13]. In the following studies, we will explain the physical mechanism of Δn and confirm the validity of MRI to reproduce the universal relation (UR) between n, R, l and k for hydrothermally-grown ZnO MSs.

3. Results and discussions

3.1 Mechanisms for redshift of the center wavelength of the WGM band in UV range

In order to explain the significant red shift of UV peak in the ZnO spherical microcavities grown by hydrothermal method, one needs to consider carefully their inner morphology and chemical bonding. Figure 1 shows the PL spectrum of a 3.7μm ZnO MS before and after it is damaged by laser illumination. Interestingly, the cavity effect of WGM is linked to the shift of UV peak of the ZnO MS. It is observed that when the ZnO MS crumbles due to laser heating, the WGM behavior disappears while the main UV peak would blue shift and split into two peaks at energies around 3.16 eV and 3.25 eV, and its intensity would also be enhanced significantly. The high-energy peak is close to the typical UV peak in polycrystalline ZnO, suggesting that part of the crumbled MS is polycrystalline ZnO. The difference in the two spectra reveals the cavity effect of MS. In comparison, the main UV peak of the PL spectrum of ZnO MS made by laser ablation is near 3.20 eV, about 0.05 eV lower than the UV peak of polycrystalline ZnO target [13]. The small red shift in that study could be due to cavity effect, excitons trapped by defects near surface, or the electron-hole plasma induced band gap renormalization effect. It has been shown that for ZnO micro cavities, higher laser power would cause a redshift of the center wavelength of the WGM lasing band [21].

 figure: Fig. 1

Fig. 1 PL spectrum of 3.7μm ZnO MS before (up) and after (down) laser damage with SEM images shown in insets.

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The SEM picture of the damaged MS reveals a porous structure inside our MS made by hydrothermal synthesis. During the growth process, it was observed that the MS is usually porous with tiny voids formed inside the MS. The formation of mesoporous structures by hydrothermal synthesis is rather typical, as reported in [22]. The surface of MS becomes smooth only after a long time growth followed by thermal annealing. The main UV peaks at 3.16 eV and 3.25eV for damaged MSs remain different from the 3.3 eV for single crystalline ZnO. Based on this study, we conclude that the interior of our MS may be comprised by polycrystalline ZnO and some sheet-like ZnO structures as observed in [16], where the main peak appears at around 3.17 eV. The larger shift (Δε ~0.3 eV) than in [13] might be the results of porous structure inside MSs. The more direct evidence would show in section 3.2

To confirm this assumption, the XPS spectrum of ZnO MS was measured, and results were given in Fig. 2. As shown in Fig. 2, the Zn 2p3/2 and O 1s peaks are composed by three main peaks. The typical binding values of Zn2+ and O2- ions in wurtize structure is 1021.80 eV ~1022.30 eV for Zn 2p3/2 and 530.90 eV ~531.5 eV for O 1s. In Zn(OH)2, these values are 1021.80 eV and 1022.70 eV for Zn 2p3/2 and 532.20 eV for O 1s. All above data were taken from [23]. On the other hand, recent investigation in 2D graphite-like ZnO (g-ZnO) also showed value of 1020.76 eV for Zn 2p3/2 [24]. Based on the comparison of our XPS data (see Fig. 2) with the above, it is concluded that our sample may contain wurtzite ZnO, g-ZnO and Zn(OH)2 crystal structures. It is worth to note that bonding related to Zn(OH)2 structures may be excluded as a result of very high annealing temperature [25]. Hence, our ZnO MS could be composed by polycrystalline and graphite-like ZnO structures. The existence of graphite-like and plate-like nanostructures in porous microstructures synthesized by similar reactants with difference reaction conditions was reported in [16].

 figure: Fig. 2

Fig. 2 XPS spectra of Zn 2p3/2 (a) and O 1s (b) in annealed ZnO MSs on silicon substrate.

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3.2 Revisiting universal relation behavior in ZnO microcavities by experimental data

Figure 3 illustrates the linear relation between the parameter KR and angular-momentum mode number l, where K = n2𝜋/𝜆 and R is the radius (edge length) of spherical (hexagonal) cavity. The data of hexagonal cavities were obtained from [26]. By doing so, the universal relation (UR) between cavity size, refractive index (including the MRI correction, Δn), resonance wavelength and mode number l can be established. Moreover, it is clearly shown that the UR has morphology dependence (Fig. 3(a)). The slopes of linear fitting of the UR line for hexagonal and spherical resonators are αhex = 1.230 ± 0.004 and αsph = 1.081 ± 0.001, respectively.

 figure: Fig. 3

Fig. 3 (a) KR values extracted from WGM peak positions observed experimentally (with MRI correction for spherical MSs) as functions of mode number for our ZnO spherical cavities (solid squares) and hexagonal microcavities (open objects) taken from [26]. (b) Illustration of the failure of constructing UR for KR values extracted from WGM peak positions observed experimentally (with the use of a constant refractive index of 2.2) for our ZnO MSs. The data with MRI correction as shown in (a) (which satisfy the UR) are plotted again for comparison. Note that same cavity size was denoted by the same color, and the width a (twice the edge length R) of hexagonal cavities is related to the diameter d of a circle with the same enclosed area via a = 1.0996 d [27].

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For hexagonal dielectric resonators, the UR was implied using numerical or semi-classical analysis [28] for lowest-loss modes, 20 ≤ Re(KR)/n ≤ 60. From such calculation, we could get αnum = 1.236 and αsemi = 1.237 with n = 2.2, in good agreement with the above αhex.

For a certain size, the slope of KR line is independent of refractive index. However, it is not the case for its intercept (see Fig. 3(b)). For ZnO MSs in this current work, without utilizing corrected refractive index in MRI model the UR could not be established. In Fig. 3(b), the deviation of KR lines from the UR line for different sizes of spherical cavities indicates the importance of adding Δn and dispersion effect. The existence of Δn is a result of porous structure in hydrothermal-based ZnO MS. For ZnO microcavities prepared by other methods, such as thermal evaporated ZnO microwires [26] and laser ablated ZnO MSs [9,13], implementation of Δn for calculating WGM resonances is negligible. The ZnO synthesized by latter methods might be more robust than the first one: no damage occurs even at high laser power [29,30].

The size independence of Δn as shown in Table 1 is therefore explained by the arbitrary character of intrinsic porosity concentration inside hydrothermal-based MSs. There is a correlation between Δn and deviation from the standard UR line of the line calculated with n=2.2 for each size. On the other hand, there might be an existence of correlation between Δn and the UV peak shift. This is consistent with the observation in [13]. When Δn is negligible due to more robust MSs, much smaller shift (~0.05 eV) was observed, leaving only the effects due to cavity, excitons trapped to surface defects, and many-body effects. It is thus shown that the porous property is one of the reasons causing the UV peak shift.

Tables Icon

Table 1. Δn for different resonator diameters.

It is noted that even though the MRI model works well for the prediction of WGM behavior in visible range, it still has limitation in UV. At high l values for certain sizes, KR values still deviate from the UR line. This problem could be fixed by including the exciton-polariton effect in a future work [31].

4. Conclusions

In summary, we have presented a relation between size, inner structure and WGM behavior in ZnO MSs grown by hydrothermal synthesis. The possible mechanisms, including cavity effect and porous structure inside MSs, for the peak shift of UV emission are revealed. The PL spectra also suggest that our MSs might be composed by polycrystalline and graphite-like ZnO. Furthermore, the universal relation for the parameter KR for MSs of various sizes is found after taking into account the refractive index correction in the MRI model. Our study is important for understanding the effects of refractive index and intrinsic structural properties on WGMs, which are often underestimated. In order to predict WGMs in UV range more precisely, the dispersion due to exciton-polariton effect needs to be considered [31].

Funding

Ministry of Science and Technology, Taiwan (MOST 104-2112-M-001).

Acknowledgments

Ngo thanks Prof. D. Nakamura and Prof. M. Ashida for fruitful discussions.

References and Links

1. M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009). [CrossRef]   [PubMed]  

2. C. H. Ahn, Y. Y. Kim, D. C. Kim, S. K. Mohanta, and H. K. Cho, “A comparative analysis of deep level emission in ZnO layers deposited by various methods,” J. Appl. Phys. 105(1), 013502 (2009). [CrossRef]  

3. W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006). [CrossRef]  

4. R. Könenkamp, R. C. Word, and C. Schlegel, “Vertical nanowire light emitting diode,” Appl. Phys. Lett. 85(24), 6004–6006 (2004). [CrossRef]  

5. Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005). [CrossRef]  

6. M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001). [CrossRef]   [PubMed]  

7. C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014). [CrossRef]  

8. A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010). [CrossRef]  

9. S. Okamoto, K. Inaba, T. Iida, H. Ishihara, S. Ichikawa, and M. Ashida, “Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials,” Sci. Rep. 4, 5186 (2014). [CrossRef]   [PubMed]  

10. R. S. Moirangthem, P. J. Cheng, P. C. Chien, B. T. Ngo, S. W. Chang, C. H. Tien, and Y. C. Chang, “Optical cavity modes of a single crystalline zinc oxide microsphere,” Opt. Express 21(3), 3010–3020 (2013). [CrossRef]   [PubMed]  

11. K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012). [CrossRef]  

12. S. Okamoto, Y. Minowa, and M. Ashida, “White light lasing of ZnO microspheres fabricated by laser ablation,” Proc. SPIE 8263, 82630K (2012). [CrossRef]  

13. D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015). [CrossRef]  

14. N. Tetsuyama, K. Fusazaki, Y. Mizokami, T. Shimogaki, M. Higashihata, D. Nakamura, and T. Okada, “Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film,” Opt. Express 22(8), 10026–10031 (2014). [CrossRef]   [PubMed]  

15. Y. F. Zhu, D. H. Fan, and W. Z. Shen, “Template-free synthesis of zinc oxide hollow microspheres in aqueous solution at low temperature,” J. Phys. Chem. C 111(50), 18629–18635 (2007). [CrossRef]  

16. C. L. Kuo, T. J. Kuo, and M. H. Huang, “Hydrothermal synthesis of ZnO microspheres and hexagonal microrods with sheetlike and platelike nanostructures,” J. Phys. Chem. B 109(43), 20115–20121 (2005). [CrossRef]   [PubMed]  

17. H. B. T. Ngo, P. C. H. Chien, Y. D. Chen, S. H. Wu, F. C. Hsiao, L. N. Nguyen, and Y. C. Chang, “ Whispering gallery mode biosensing – a detailed study on ZnO microspheres,” in the series IFMBE Proceedings Vol. 46, V. V. Toi, T. H. L. Phuong, ed. (Springer, 2015), pp. 21–24.

18. R. K. Chang and A. J. Campillo, Optical Processes in Microcavities (World Sciencetific, 1996), Ch. 5.

19. J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, “Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail,” Appl. Phys. Lett. 92(26), 263102 (2008). [CrossRef]  

20. S. Spillane, “Fiber-coupled ultra-high Q microresonators for nonlinear and quantum optics,” Ph.D. thesis, California Inst. of Technol. (2004).

21. J. Dai, C. Xu, T. Nakamura, Y. Wang, J. Li, and Y. Lin, “Electron-hole plasma induced band gap renormalization in ZnO microlaser cavities,” Opt. Express 22(23), 28831–28837 (2014). [CrossRef]   [PubMed]  

22. J. H. Pan, H. Dou, Z. Xiong, C. Xu, J. Ma, and X. S. Zhao, “Porous photocatalysts for advanced water purifications,” J. Mater. Chem. 20(22), 4512–4528 (2010). [CrossRef]  

23. NIST X-ray Photoelectron Spectroscopy Database, http://srdata.nist.gov/xps/Default.aspx.

24. Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014). [CrossRef]   [PubMed]  

25. M. Wang, L. Jiang, E. J. Kim, and S. H. Hahn, “Electronic structure and optical properties of Zn(OH)2: LDA+U calculations and intense yellow luminescence,” RSC Advances 5(106), 87496–87503 (2015). [CrossRef]  

26. G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011). [CrossRef]  

27. T. Nobis and M. Grundmann, “Low-order optical whispering-gallery modes in hexagonal,” Phys. Rev. A 72(6), 063806 (2005). [CrossRef]  

28. J. Wiersig, “Hexagonal dielectric resonators and micro crystal lasers,” Phys. Rev. A 67(2), 023807 (2003). [CrossRef]  

29. D. Nakamura, Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motoka, Nishi-ku, Fukuoka 819–0395, Japan (personal communication, 2015).

30. M. Ashida, Graduate School of Engineering Science, Osaka University, 1–3 Machikaneyana-cho, Toyobaka, Osaka 560 −8531, Japan (personal communication, 2015).

31. P. C. H. Chien, T. H. B. Ngo, Research Center for Applied Sciences, Academia Sinica, Taipei, 11529, and Y. C. Chang are preparing a manuscript to be called “Theory of lineshape of WGM enhanced photoluminescence in ZnO microsphere with exciton-polariton effect”.

References

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  1. M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
    [Crossref] [PubMed]
  2. C. H. Ahn, Y. Y. Kim, D. C. Kim, S. K. Mohanta, and H. K. Cho, “A comparative analysis of deep level emission in ZnO layers deposited by various methods,” J. Appl. Phys. 105(1), 013502 (2009).
    [Crossref]
  3. W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
    [Crossref]
  4. R. Könenkamp, R. C. Word, and C. Schlegel, “Vertical nanowire light emitting diode,” Appl. Phys. Lett. 85(24), 6004–6006 (2004).
    [Crossref]
  5. Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
    [Crossref]
  6. M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
    [Crossref] [PubMed]
  7. C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014).
    [Crossref]
  8. A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
    [Crossref]
  9. S. Okamoto, K. Inaba, T. Iida, H. Ishihara, S. Ichikawa, and M. Ashida, “Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials,” Sci. Rep. 4, 5186 (2014).
    [Crossref] [PubMed]
  10. R. S. Moirangthem, P. J. Cheng, P. C. Chien, B. T. Ngo, S. W. Chang, C. H. Tien, and Y. C. Chang, “Optical cavity modes of a single crystalline zinc oxide microsphere,” Opt. Express 21(3), 3010–3020 (2013).
    [Crossref] [PubMed]
  11. K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012).
    [Crossref]
  12. S. Okamoto, Y. Minowa, and M. Ashida, “White light lasing of ZnO microspheres fabricated by laser ablation,” Proc. SPIE 8263, 82630K (2012).
    [Crossref]
  13. D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015).
    [Crossref]
  14. N. Tetsuyama, K. Fusazaki, Y. Mizokami, T. Shimogaki, M. Higashihata, D. Nakamura, and T. Okada, “Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film,” Opt. Express 22(8), 10026–10031 (2014).
    [Crossref] [PubMed]
  15. Y. F. Zhu, D. H. Fan, and W. Z. Shen, “Template-free synthesis of zinc oxide hollow microspheres in aqueous solution at low temperature,” J. Phys. Chem. C 111(50), 18629–18635 (2007).
    [Crossref]
  16. C. L. Kuo, T. J. Kuo, and M. H. Huang, “Hydrothermal synthesis of ZnO microspheres and hexagonal microrods with sheetlike and platelike nanostructures,” J. Phys. Chem. B 109(43), 20115–20121 (2005).
    [Crossref] [PubMed]
  17. H. B. T. Ngo, P. C. H. Chien, Y. D. Chen, S. H. Wu, F. C. Hsiao, L. N. Nguyen, and Y. C. Chang, “ Whispering gallery mode biosensing – a detailed study on ZnO microspheres,” in the series IFMBE Proceedings Vol. 46, V. V. Toi, T. H. L. Phuong, ed. (Springer, 2015), pp. 21–24.
  18. R. K. Chang and A. J. Campillo, Optical Processes in Microcavities (World Sciencetific, 1996), Ch. 5.
  19. J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, “Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail,” Appl. Phys. Lett. 92(26), 263102 (2008).
    [Crossref]
  20. S. Spillane, “Fiber-coupled ultra-high Q microresonators for nonlinear and quantum optics,” Ph.D. thesis, California Inst. of Technol. (2004).
  21. J. Dai, C. Xu, T. Nakamura, Y. Wang, J. Li, and Y. Lin, “Electron-hole plasma induced band gap renormalization in ZnO microlaser cavities,” Opt. Express 22(23), 28831–28837 (2014).
    [Crossref] [PubMed]
  22. J. H. Pan, H. Dou, Z. Xiong, C. Xu, J. Ma, and X. S. Zhao, “Porous photocatalysts for advanced water purifications,” J. Mater. Chem. 20(22), 4512–4528 (2010).
    [Crossref]
  23. NIST X-ray Photoelectron Spectroscopy Database, http://srdata.nist.gov/xps/Default.aspx .
  24. Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
    [Crossref] [PubMed]
  25. M. Wang, L. Jiang, E. J. Kim, and S. H. Hahn, “Electronic structure and optical properties of Zn(OH)2: LDA+U calculations and intense yellow luminescence,” RSC Advances 5(106), 87496–87503 (2015).
    [Crossref]
  26. G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011).
    [Crossref]
  27. T. Nobis and M. Grundmann, “Low-order optical whispering-gallery modes in hexagonal,” Phys. Rev. A 72(6), 063806 (2005).
    [Crossref]
  28. J. Wiersig, “Hexagonal dielectric resonators and micro crystal lasers,” Phys. Rev. A 67(2), 023807 (2003).
    [Crossref]
  29. D. Nakamura, Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motoka, Nishi-ku, Fukuoka 819–0395, Japan (personal communication, 2015).
  30. M. Ashida, Graduate School of Engineering Science, Osaka University, 1–3 Machikaneyana-cho, Toyobaka, Osaka 560 −8531, Japan (personal communication, 2015).
  31. P. C. H. Chien, T. H. B. Ngo, Research Center for Applied Sciences, Academia Sinica, Taipei, 11529, and Y. C. Chang are preparing a manuscript to be called “Theory of lineshape of WGM enhanced photoluminescence in ZnO microsphere with exciton-polariton effect”.

2015 (2)

D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015).
[Crossref]

M. Wang, L. Jiang, E. J. Kim, and S. H. Hahn, “Electronic structure and optical properties of Zn(OH)2: LDA+U calculations and intense yellow luminescence,” RSC Advances 5(106), 87496–87503 (2015).
[Crossref]

2014 (5)

J. Dai, C. Xu, T. Nakamura, Y. Wang, J. Li, and Y. Lin, “Electron-hole plasma induced band gap renormalization in ZnO microlaser cavities,” Opt. Express 22(23), 28831–28837 (2014).
[Crossref] [PubMed]

Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
[Crossref] [PubMed]

N. Tetsuyama, K. Fusazaki, Y. Mizokami, T. Shimogaki, M. Higashihata, D. Nakamura, and T. Okada, “Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film,” Opt. Express 22(8), 10026–10031 (2014).
[Crossref] [PubMed]

S. Okamoto, K. Inaba, T. Iida, H. Ishihara, S. Ichikawa, and M. Ashida, “Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials,” Sci. Rep. 4, 5186 (2014).
[Crossref] [PubMed]

C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014).
[Crossref]

2013 (1)

2012 (2)

K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012).
[Crossref]

S. Okamoto, Y. Minowa, and M. Ashida, “White light lasing of ZnO microspheres fabricated by laser ablation,” Proc. SPIE 8263, 82630K (2012).
[Crossref]

2011 (1)

G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011).
[Crossref]

2010 (2)

J. H. Pan, H. Dou, Z. Xiong, C. Xu, J. Ma, and X. S. Zhao, “Porous photocatalysts for advanced water purifications,” J. Mater. Chem. 20(22), 4512–4528 (2010).
[Crossref]

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

2009 (2)

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

C. H. Ahn, Y. Y. Kim, D. C. Kim, S. K. Mohanta, and H. K. Cho, “A comparative analysis of deep level emission in ZnO layers deposited by various methods,” J. Appl. Phys. 105(1), 013502 (2009).
[Crossref]

2008 (1)

J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, “Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail,” Appl. Phys. Lett. 92(26), 263102 (2008).
[Crossref]

2007 (1)

Y. F. Zhu, D. H. Fan, and W. Z. Shen, “Template-free synthesis of zinc oxide hollow microspheres in aqueous solution at low temperature,” J. Phys. Chem. C 111(50), 18629–18635 (2007).
[Crossref]

2006 (1)

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

2005 (3)

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

C. L. Kuo, T. J. Kuo, and M. H. Huang, “Hydrothermal synthesis of ZnO microspheres and hexagonal microrods with sheetlike and platelike nanostructures,” J. Phys. Chem. B 109(43), 20115–20121 (2005).
[Crossref] [PubMed]

T. Nobis and M. Grundmann, “Low-order optical whispering-gallery modes in hexagonal,” Phys. Rev. A 72(6), 063806 (2005).
[Crossref]

2004 (1)

R. Könenkamp, R. C. Word, and C. Schlegel, “Vertical nanowire light emitting diode,” Appl. Phys. Lett. 85(24), 6004–6006 (2004).
[Crossref]

2003 (1)

J. Wiersig, “Hexagonal dielectric resonators and micro crystal lasers,” Phys. Rev. A 67(2), 023807 (2003).
[Crossref]

2001 (1)

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Ahn, C. H.

C. H. Ahn, Y. Y. Kim, D. C. Kim, S. K. Mohanta, and H. K. Cho, “A comparative analysis of deep level emission in ZnO layers deposited by various methods,” J. Appl. Phys. 105(1), 013502 (2009).
[Crossref]

Ahn, Y. H.

J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, “Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail,” Appl. Phys. Lett. 92(26), 263102 (2008).
[Crossref]

Alivov, Y. I.

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

Al-Suleiman, M.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Ashida, M.

S. Okamoto, K. Inaba, T. Iida, H. Ishihara, S. Ichikawa, and M. Ashida, “Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials,” Sci. Rep. 4, 5186 (2014).
[Crossref] [PubMed]

S. Okamoto, Y. Minowa, and M. Ashida, “White light lasing of ZnO microspheres fabricated by laser ablation,” Proc. SPIE 8263, 82630K (2012).
[Crossref]

Avrutin, V.

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

Bakin, A.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Behrends, A.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Boukos, N.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Cao, B. Q.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Chang, S. W.

Chang, Y. C.

Che Mofor, A.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Cheng, P. J.

Chiasera, A.

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

Chien, P. C.

Cho, H. K.

C. H. Ahn, Y. Y. Kim, D. C. Kim, S. K. Mohanta, and H. K. Cho, “A comparative analysis of deep level emission in ZnO layers deposited by various methods,” J. Appl. Phys. 105(1), 013502 (2009).
[Crossref]

Cho, S. J.

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

Conti, G. N.

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

Czekalla, C.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Dai, G.

G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011).
[Crossref]

Dai, J.

C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014).
[Crossref]

J. Dai, C. Xu, T. Nakamura, Y. Wang, J. Li, and Y. Lin, “Electron-hole plasma induced band gap renormalization in ZnO microlaser cavities,” Opt. Express 22(23), 28831–28837 (2014).
[Crossref] [PubMed]

Dogan, S.

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

Dou, H.

J. H. Pan, H. Dou, Z. Xiong, C. Xu, J. Ma, and X. S. Zhao, “Porous photocatalysts for advanced water purifications,” J. Mater. Chem. 20(22), 4512–4528 (2010).
[Crossref]

Dou, S. X.

Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
[Crossref] [PubMed]

Dou, Y.

Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
[Crossref] [PubMed]

Dumeige, Y.

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

El-Shaer, A.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Fan, D. H.

Y. F. Zhu, D. H. Fan, and W. Z. Shen, “Template-free synthesis of zinc oxide hollow microspheres in aqueous solution at low temperature,” J. Phys. Chem. C 111(50), 18629–18635 (2007).
[Crossref]

Feick, H.

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Féron, P.

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

Ferrari, M.

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

Fusazaki, K.

N. Tetsuyama, K. Fusazaki, Y. Mizokami, T. Shimogaki, M. Higashihata, D. Nakamura, and T. Okada, “Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film,” Opt. Express 22(8), 10026–10031 (2014).
[Crossref] [PubMed]

K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012).
[Crossref]

Grundmann, M.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

T. Nobis and M. Grundmann, “Low-order optical whispering-gallery modes in hexagonal,” Phys. Rev. A 72(6), 063806 (2005).
[Crossref]

Gu, S. L.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Guinard, J.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Hahn, S. H.

M. Wang, L. Jiang, E. J. Kim, and S. H. Hahn, “Electronic structure and optical properties of Zn(OH)2: LDA+U calculations and intense yellow luminescence,” RSC Advances 5(106), 87496–87503 (2015).
[Crossref]

Hang, Y.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Higashihata, M.

D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015).
[Crossref]

N. Tetsuyama, K. Fusazaki, Y. Mizokami, T. Shimogaki, M. Higashihata, D. Nakamura, and T. Okada, “Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film,” Opt. Express 22(8), 10026–10031 (2014).
[Crossref] [PubMed]

K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012).
[Crossref]

Huang, M. H.

C. L. Kuo, T. J. Kuo, and M. H. Huang, “Hydrothermal synthesis of ZnO microspheres and hexagonal microrods with sheetlike and platelike nanostructures,” J. Phys. Chem. B 109(43), 20115–20121 (2005).
[Crossref] [PubMed]

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Hwang, S. M.

Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
[Crossref] [PubMed]

Ichikawa, S.

S. Okamoto, K. Inaba, T. Iida, H. Ishihara, S. Ichikawa, and M. Ashida, “Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials,” Sci. Rep. 4, 5186 (2014).
[Crossref] [PubMed]

Iida, T.

S. Okamoto, K. Inaba, T. Iida, H. Ishihara, S. Ichikawa, and M. Ashida, “Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials,” Sci. Rep. 4, 5186 (2014).
[Crossref] [PubMed]

Inaba, K.

S. Okamoto, K. Inaba, T. Iida, H. Ishihara, S. Ichikawa, and M. Ashida, “Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials,” Sci. Rep. 4, 5186 (2014).
[Crossref] [PubMed]

Ishihara, H.

S. Okamoto, K. Inaba, T. Iida, H. Ishihara, S. Ichikawa, and M. Ashida, “Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials,” Sci. Rep. 4, 5186 (2014).
[Crossref] [PubMed]

Jestin, Y.

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

Jiang, L.

M. Wang, L. Jiang, E. J. Kim, and S. H. Hahn, “Electronic structure and optical properties of Zn(OH)2: LDA+U calculations and intense yellow luminescence,” RSC Advances 5(106), 87496–87503 (2015).
[Crossref]

Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
[Crossref] [PubMed]

Kim, D. C.

C. H. Ahn, Y. Y. Kim, D. C. Kim, S. K. Mohanta, and H. K. Cho, “A comparative analysis of deep level emission in ZnO layers deposited by various methods,” J. Appl. Phys. 105(1), 013502 (2009).
[Crossref]

Kim, E. J.

M. Wang, L. Jiang, E. J. Kim, and S. H. Hahn, “Electronic structure and optical properties of Zn(OH)2: LDA+U calculations and intense yellow luminescence,” RSC Advances 5(106), 87496–87503 (2015).
[Crossref]

Kim, J. H.

Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
[Crossref] [PubMed]

Kim, Y. Y.

C. H. Ahn, Y. Y. Kim, D. C. Kim, S. K. Mohanta, and H. K. Cho, “A comparative analysis of deep level emission in ZnO layers deposited by various methods,” J. Appl. Phys. 105(1), 013502 (2009).
[Crossref]

Kind, H.

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Koh, K. H.

J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, “Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail,” Appl. Phys. Lett. 92(26), 263102 (2008).
[Crossref]

Könenkamp, R.

R. Könenkamp, R. C. Word, and C. Schlegel, “Vertical nanowire light emitting diode,” Appl. Phys. Lett. 85(24), 6004–6006 (2004).
[Crossref]

Koshizaki, N.

K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012).
[Crossref]

Kuo, C. L.

C. L. Kuo, T. J. Kuo, and M. H. Huang, “Hydrothermal synthesis of ZnO microspheres and hexagonal microrods with sheetlike and platelike nanostructures,” J. Phys. Chem. B 109(43), 20115–20121 (2005).
[Crossref] [PubMed]

Kuo, T. J.

C. L. Kuo, T. J. Kuo, and M. H. Huang, “Hydrothermal synthesis of ZnO microspheres and hexagonal microrods with sheetlike and platelike nanostructures,” J. Phys. Chem. B 109(43), 20115–20121 (2005).
[Crossref] [PubMed]

Kwack, H. S.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Le Si Dang, D.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Lee, S.

J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, “Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail,” Appl. Phys. Lett. 92(26), 263102 (2008).
[Crossref]

Li, J.

J. Dai, C. Xu, T. Nakamura, Y. Wang, J. Li, and Y. Lin, “Electron-hole plasma induced band gap renormalization in ZnO microlaser cavities,” Opt. Express 22(23), 28831–28837 (2014).
[Crossref] [PubMed]

C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014).
[Crossref]

Liao, T.

Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
[Crossref] [PubMed]

Lin, R.

G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011).
[Crossref]

Lin, Y.

J. Dai, C. Xu, T. Nakamura, Y. Wang, J. Li, and Y. Lin, “Electron-hole plasma induced band gap renormalization in ZnO microlaser cavities,” Opt. Express 22(23), 28831–28837 (2014).
[Crossref] [PubMed]

C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014).
[Crossref]

Liu, C.

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

Liu, J.

J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, “Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail,” Appl. Phys. Lett. 92(26), 263102 (2008).
[Crossref]

Liu, S. M.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Liu, W.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Lorenz, M.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Ma, J.

J. H. Pan, H. Dou, Z. Xiong, C. Xu, J. Ma, and X. S. Zhao, “Porous photocatalysts for advanced water purifications,” J. Mater. Chem. 20(22), 4512–4528 (2010).
[Crossref]

Mao, S.

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Minowa, Y.

S. Okamoto, Y. Minowa, and M. Ashida, “White light lasing of ZnO microspheres fabricated by laser ablation,” Proc. SPIE 8263, 82630K (2012).
[Crossref]

Mizokami, Y.

D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015).
[Crossref]

N. Tetsuyama, K. Fusazaki, Y. Mizokami, T. Shimogaki, M. Higashihata, D. Nakamura, and T. Okada, “Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film,” Opt. Express 22(8), 10026–10031 (2014).
[Crossref] [PubMed]

Mohanta, S. K.

C. H. Ahn, Y. Y. Kim, D. C. Kim, S. K. Mohanta, and H. K. Cho, “A comparative analysis of deep level emission in ZnO layers deposited by various methods,” J. Appl. Phys. 105(1), 013502 (2009).
[Crossref]

Moirangthem, R. S.

Morkoç, H.

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

Nakamura, D.

D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015).
[Crossref]

N. Tetsuyama, K. Fusazaki, Y. Mizokami, T. Shimogaki, M. Higashihata, D. Nakamura, and T. Okada, “Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film,” Opt. Express 22(8), 10026–10031 (2014).
[Crossref] [PubMed]

K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012).
[Crossref]

Nakamura, T.

Ngo, B. T.

Nobis, T.

T. Nobis and M. Grundmann, “Low-order optical whispering-gallery modes in hexagonal,” Phys. Rev. A 72(6), 063806 (2005).
[Crossref]

Nur, O.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Okada, T.

D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015).
[Crossref]

N. Tetsuyama, K. Fusazaki, Y. Mizokami, T. Shimogaki, M. Higashihata, D. Nakamura, and T. Okada, “Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film,” Opt. Express 22(8), 10026–10031 (2014).
[Crossref] [PubMed]

K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012).
[Crossref]

Okamoto, S.

S. Okamoto, K. Inaba, T. Iida, H. Ishihara, S. Ichikawa, and M. Ashida, “Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials,” Sci. Rep. 4, 5186 (2014).
[Crossref] [PubMed]

S. Okamoto, Y. Minowa, and M. Ashida, “White light lasing of ZnO microspheres fabricated by laser ablation,” Proc. SPIE 8263, 82630K (2012).
[Crossref]

Okazaki, K.

K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012).
[Crossref]

Özgür, Ü.

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

Pan, A.

G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011).
[Crossref]

Pan, J. H.

J. H. Pan, H. Dou, Z. Xiong, C. Xu, J. Ma, and X. S. Zhao, “Porous photocatalysts for advanced water purifications,” J. Mater. Chem. 20(22), 4512–4528 (2010).
[Crossref]

Park, J. Y.

J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, “Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail,” Appl. Phys. Lett. 92(26), 263102 (2008).
[Crossref]

Park, K. H.

J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, “Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail,” Appl. Phys. Lett. 92(26), 263102 (2008).
[Crossref]

Park, M. S.

Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
[Crossref] [PubMed]

Pelli, S.

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

Postels, B.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Reshchikov, M. A.

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

Righini, G. C.

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

Russo, R.

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Sato, Y.

D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015).
[Crossref]

Schlegel, C.

R. Könenkamp, R. C. Word, and C. Schlegel, “Vertical nanowire light emitting diode,” Appl. Phys. Lett. 85(24), 6004–6006 (2004).
[Crossref]

Shen, W. Z.

Y. F. Zhu, D. H. Fan, and W. Z. Shen, “Template-free synthesis of zinc oxide hollow microspheres in aqueous solution at low temperature,” J. Phys. Chem. C 111(50), 18629–18635 (2007).
[Crossref]

Shi, Y.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Shi, Z.

C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014).
[Crossref]

Shimogaki, T.

D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015).
[Crossref]

N. Tetsuyama, K. Fusazaki, Y. Mizokami, T. Shimogaki, M. Higashihata, D. Nakamura, and T. Okada, “Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film,” Opt. Express 22(8), 10026–10031 (2014).
[Crossref] [PubMed]

K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012).
[Crossref]

Soria, S.

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

Sun, Z.

Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
[Crossref] [PubMed]

Teke, A.

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

Tetsuyama, N.

D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015).
[Crossref]

N. Tetsuyama, K. Fusazaki, Y. Mizokami, T. Shimogaki, M. Higashihata, D. Nakamura, and T. Okada, “Ultraviolet electroluminescence from hetero p-n junction between a single ZnO microsphere and p-GaN thin film,” Opt. Express 22(8), 10026–10031 (2014).
[Crossref] [PubMed]

Tien, C. H.

Travlos, A.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Waag, A.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Wan, Q.

G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011).
[Crossref]

Wang, M.

M. Wang, L. Jiang, E. J. Kim, and S. H. Hahn, “Electronic structure and optical properties of Zn(OH)2: LDA+U calculations and intense yellow luminescence,” RSC Advances 5(106), 87496–87503 (2015).
[Crossref]

Wang, Y.

Weber, E.

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Wiersig, J.

J. Wiersig, “Hexagonal dielectric resonators and micro crystal lasers,” Phys. Rev. A 67(2), 023807 (2003).
[Crossref]

Willander, M.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Word, R. C.

R. Könenkamp, R. C. Word, and C. Schlegel, “Vertical nanowire light emitting diode,” Appl. Phys. Lett. 85(24), 6004–6006 (2004).
[Crossref]

Wu, Y.

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Xiong, Z.

J. H. Pan, H. Dou, Z. Xiong, C. Xu, J. Ma, and X. S. Zhao, “Porous photocatalysts for advanced water purifications,” J. Mater. Chem. 20(22), 4512–4528 (2010).
[Crossref]

Xu, C.

J. Dai, C. Xu, T. Nakamura, Y. Wang, J. Li, and Y. Lin, “Electron-hole plasma induced band gap renormalization in ZnO microlaser cavities,” Opt. Express 22(23), 28831–28837 (2014).
[Crossref] [PubMed]

C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014).
[Crossref]

J. H. Pan, H. Dou, Z. Xiong, C. Xu, J. Ma, and X. S. Zhao, “Porous photocatalysts for advanced water purifications,” J. Mater. Chem. 20(22), 4512–4528 (2010).
[Crossref]

Yan, H.

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Yang, L. L.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Yang, P.

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Ye, J. D.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Zhang, C. L.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Zhang, Q.

G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011).
[Crossref]

Zhang, R.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Zhang, Y.

G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011).
[Crossref]

Zhao, Q. X.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Zhao, X. S.

J. H. Pan, H. Dou, Z. Xiong, C. Xu, J. Ma, and X. S. Zhao, “Porous photocatalysts for advanced water purifications,” J. Mater. Chem. 20(22), 4512–4528 (2010).
[Crossref]

Zheng, Y. D.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Zhou, X.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Zhu, G.

C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014).
[Crossref]

C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014).
[Crossref]

Zhu, S. M.

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

Zhu, Y. F.

Y. F. Zhu, D. H. Fan, and W. Z. Shen, “Template-free synthesis of zinc oxide hollow microspheres in aqueous solution at low temperature,” J. Phys. Chem. C 111(50), 18629–18635 (2007).
[Crossref]

Zimmermann, G.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Zou, B.

G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011).
[Crossref]

Zúñiga Pérez, J.

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Appl. Phys. Lett. (4)

W. Liu, S. L. Gu, J. D. Ye, S. M. Zhu, S. M. Liu, X. Zhou, R. Zhang, Y. Shi, Y. D. Zheng, Y. Hang, and C. L. Zhang, “Blue, yellow ZnO homostructural light-emitting diode realized by metalorganic chemical vapor deposition technique,” Appl. Phys. Lett. 88(9), 092101 (2006).
[Crossref]

R. Könenkamp, R. C. Word, and C. Schlegel, “Vertical nanowire light emitting diode,” Appl. Phys. Lett. 85(24), 6004–6006 (2004).
[Crossref]

K. Okazaki, T. Shimogaki, K. Fusazaki, M. Higashihata, D. Nakamura, N. Koshizaki, and T. Okada, “Ultraviolet whispering-gallery-mode lasing in ZnO micro/nano sphere crystal,” Appl. Phys. Lett. 101(21), 211105 (2012).
[Crossref]

J. Liu, S. Lee, Y. H. Ahn, J. Y. Park, K. H. Koh, and K. H. Park, “Identification of dispersion-dependent hexagonal cavity modes of an individual ZnO nanonail,” Appl. Phys. Lett. 92(26), 263102 (2008).
[Crossref]

J. Appl. Phys. (3)

G. Dai, Y. Zhang, R. Lin, Q. Wan, Q. Zhang, A. Pan, and B. Zou, “Visible whispering gallery modes in ZnO microwires with varied cross sections,” J. Appl. Phys. 110(3), 033101 (2011).
[Crossref]

Ü. Özgür, Y. I. Alivov, C. Liu, A. Teke, M. A. Reshchikov, S. Doğan, V. Avrutin, S. J. Cho, and H. Morkoç, “A comprehensive review of ZnO materials and devices,” J. Appl. Phys. 98(4), 041301 (2005).
[Crossref]

C. H. Ahn, Y. Y. Kim, D. C. Kim, S. K. Mohanta, and H. K. Cho, “A comparative analysis of deep level emission in ZnO layers deposited by various methods,” J. Appl. Phys. 105(1), 013502 (2009).
[Crossref]

J. Laser Micro Nanoeng. (1)

D. Nakamura, N. Tetsuyama, T. Shimogaki, Y. Sato, Y. Mizokami, M. Higashihata, and T. Okada, “Optical characterization of ZnO microspheres produced by laser ablation in air,” J. Laser Micro Nanoeng. 10(2), 162–165 (2015).
[Crossref]

J. Mater. Chem. (1)

J. H. Pan, H. Dou, Z. Xiong, C. Xu, J. Ma, and X. S. Zhao, “Porous photocatalysts for advanced water purifications,” J. Mater. Chem. 20(22), 4512–4528 (2010).
[Crossref]

J. Phys. Chem. B (1)

C. L. Kuo, T. J. Kuo, and M. H. Huang, “Hydrothermal synthesis of ZnO microspheres and hexagonal microrods with sheetlike and platelike nanostructures,” J. Phys. Chem. B 109(43), 20115–20121 (2005).
[Crossref] [PubMed]

J. Phys. Chem. C (1)

Y. F. Zhu, D. H. Fan, and W. Z. Shen, “Template-free synthesis of zinc oxide hollow microspheres in aqueous solution at low temperature,” J. Phys. Chem. C 111(50), 18629–18635 (2007).
[Crossref]

Laser Photonics Rev. (2)

C. Xu, J. Dai, G. Zhu, G. Zhu, Y. Lin, J. Li, and Z. Shi, “Whispering-gallery mode lasing in ZnO microcavities,” Laser Photonics Rev. 8(4), 469–494 (2014).
[Crossref]

A. Chiasera, Y. Dumeige, P. Féron, M. Ferrari, Y. Jestin, G. N. Conti, S. Pelli, S. Soria, and G. C. Righini, “Spherical whispering-gallery mode microresonators,” Laser Photonics Rev. 4(3), 457–482 (2010).
[Crossref]

Nanotechnology (1)

M. Willander, O. Nur, Q. X. Zhao, L. L. Yang, M. Lorenz, B. Q. Cao, J. Zúñiga Pérez, C. Czekalla, G. Zimmermann, M. Grundmann, A. Bakin, A. Behrends, M. Al-Suleiman, A. El-Shaer, A. Che Mofor, B. Postels, A. Waag, N. Boukos, A. Travlos, H. S. Kwack, J. Guinard, and D. Le Si Dang, “Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers,” Nanotechnology 20(33), 332001 (2009).
[Crossref] [PubMed]

Nat. Commun. (1)

Z. Sun, T. Liao, Y. Dou, S. M. Hwang, M. S. Park, L. Jiang, J. H. Kim, and S. X. Dou, “Generalized self-assembly of scalable two-dimensional transition metal oxide nanosheets,” Nat. Commun. 5, 3813 (2014).
[Crossref] [PubMed]

Opt. Express (3)

Phys. Rev. A (2)

T. Nobis and M. Grundmann, “Low-order optical whispering-gallery modes in hexagonal,” Phys. Rev. A 72(6), 063806 (2005).
[Crossref]

J. Wiersig, “Hexagonal dielectric resonators and micro crystal lasers,” Phys. Rev. A 67(2), 023807 (2003).
[Crossref]

Proc. SPIE (1)

S. Okamoto, Y. Minowa, and M. Ashida, “White light lasing of ZnO microspheres fabricated by laser ablation,” Proc. SPIE 8263, 82630K (2012).
[Crossref]

RSC Advances (1)

M. Wang, L. Jiang, E. J. Kim, and S. H. Hahn, “Electronic structure and optical properties of Zn(OH)2: LDA+U calculations and intense yellow luminescence,” RSC Advances 5(106), 87496–87503 (2015).
[Crossref]

Sci. Rep. (1)

S. Okamoto, K. Inaba, T. Iida, H. Ishihara, S. Ichikawa, and M. Ashida, “Fabrication of single-crystalline microspheres with high sphericity from anisotropic materials,” Sci. Rep. 4, 5186 (2014).
[Crossref] [PubMed]

Science (1)

M. H. Huang, S. Mao, H. Feick, H. Yan, Y. Wu, H. Kind, E. Weber, R. Russo, and P. Yang, “Room-temperature ultraviolet nanowire nanolasers,” Science 292(5523), 1897–1899 (2001).
[Crossref] [PubMed]

Other (7)

H. B. T. Ngo, P. C. H. Chien, Y. D. Chen, S. H. Wu, F. C. Hsiao, L. N. Nguyen, and Y. C. Chang, “ Whispering gallery mode biosensing – a detailed study on ZnO microspheres,” in the series IFMBE Proceedings Vol. 46, V. V. Toi, T. H. L. Phuong, ed. (Springer, 2015), pp. 21–24.

R. K. Chang and A. J. Campillo, Optical Processes in Microcavities (World Sciencetific, 1996), Ch. 5.

D. Nakamura, Graduate School of Information Science and Electrical Engineering, Kyushu University, 744 Motoka, Nishi-ku, Fukuoka 819–0395, Japan (personal communication, 2015).

M. Ashida, Graduate School of Engineering Science, Osaka University, 1–3 Machikaneyana-cho, Toyobaka, Osaka 560 −8531, Japan (personal communication, 2015).

P. C. H. Chien, T. H. B. Ngo, Research Center for Applied Sciences, Academia Sinica, Taipei, 11529, and Y. C. Chang are preparing a manuscript to be called “Theory of lineshape of WGM enhanced photoluminescence in ZnO microsphere with exciton-polariton effect”.

NIST X-ray Photoelectron Spectroscopy Database, http://srdata.nist.gov/xps/Default.aspx .

S. Spillane, “Fiber-coupled ultra-high Q microresonators for nonlinear and quantum optics,” Ph.D. thesis, California Inst. of Technol. (2004).

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Figures (3)

Fig. 1
Fig. 1 PL spectrum of 3.7μm ZnO MS before (up) and after (down) laser damage with SEM images shown in insets.
Fig. 2
Fig. 2 XPS spectra of Zn 2p3/2 (a) and O 1s (b) in annealed ZnO MSs on silicon substrate.
Fig. 3
Fig. 3 (a) KR values extracted from WGM peak positions observed experimentally (with MRI correction for spherical MSs) as functions of mode number for our ZnO spherical cavities (solid squares) and hexagonal microcavities (open objects) taken from [26]. (b) Illustration of the failure of constructing UR for KR values extracted from WGM peak positions observed experimentally (with the use of a constant refractive index of 2.2) for our ZnO MSs. The data with MRI correction as shown in (a) (which satisfy the UR) are plotted again for comparison. Note that same cavity size was denoted by the same color, and the width a (twice the edge length R) of hexagonal cavities is related to the diameter d of a circle with the same enclosed area via a = 1.0996 d [27].

Tables (1)

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Table 1 Δn for different resonator diameters.

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