Open Access
Add to BibSonomy
Abstract
Passively Q-switched operation of Nd:YAP/Cr4+:YAG/YVO4 Raman lasers with 816 and 890 cm-1 shifts were demonstrated. A Cr4+:YAG/YAG composite crystal was utilized for the passively Q-switched operation. Using an output coupler with different transmittance at both first-Stokes wavelengths, the single first-Stokes waves at 1183.7 nm and 1194.6 nm were obtained in X(ZZ)X and X(YY)X Raman configurations, respectively. Under an absorbed pump power of 8.21 W, the maximum output power of 0.85 W and 0.76 W were achieved, corresponding to the conversion efficiency of 10.4% and 9.3%, respectively. Experimental results show that although the transmittance losses of both Stokes wavelengths were quite different, their thresholds were similar and very close to that of the passively Q-switched fundamental wave in the cavity. The pulse repetition frequency was mainly determined by the Raman conversion efficiency. These laser output characteristics have some reference value for the design of passively Q-switched Raman lasers.
© 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
1. Introduction
Stimulated Raman Scattering is widely accepted as an efficient frequency conversion technology to generate new wavelength emissions. Solid-state Raman lasers have been extensively studied in recent years, and there are a variety of crystals having been proved as solid Raman gain materials [1–5]. Vanadate crystals have attracted much attention for Raman operation owing to their strong Raman gain and superior physic properties [6–9]. Especially, the YVO4 crystal as one of the most represented vanadate crystals has attracted great interest. The Raman gain coefficient corresponding to the strongest SRS-active vibration mode of 890 cm-1was greater than 4.5 cm/GW [10]. In addition to this strongest vibration mode, there are also other vibration modes such as 838, 816, 376, and 259 cm-1 that could be used for extending the laser spectral based on Raman conversion. Additionally, the YVO4 crystal is categorized as optical anisotropic crystal with Raman spectral strongly depending on different polarization configurations [11,12]. Most of the researches were focused on YVO4 Raman lasers with the Raman shift of 890 cm-1 and 259 cm-1 [13–17]. In recent years, the Raman lasers based on the Raman shift of 816 cm-1 in YVO4 have attracted increasing research interests. In 2015, Lin et al. reported the 270 mW output power and 5.8% conversion efficiency for first-Stokes emission at 1168.6 nm with the Raman shift of 816 cm-1 in a passively Q-switched c-cut Nd:YVO4 self-Raman laser [18]. In 2018, Wang et al. reported the 1164.4 nm and 1174.7 nm dual-wavelengths Raman emission with the Raman shifts of 816 cm-1 and 890 cm-1 in a passively Q-switched Nd:GdVO4/YVO4 Raman microchip laser. The output power of 104 mW and conversion efficiency of 1.5% were obtained [19]. In the same year, Wei et al. reported orthogonally polarized emission at 1165.2 nm and 1175.4 nm with the Raman frequency shifts of 816 cm-1 and 890 cm-1 in YVO4 crystal operation derived by a passively Q-switched Nd:YAG/YAG/Cr4+:YAG/YAG composite laser. The overall output power of approximately 280 mW and the conversion efficiency of 4% were realized [20]. In 2019, Fan et al. reported the multi- wavelength outputs (1168.4, 1176, 1178.7 and 1201.6 nm) in a continuous-wave YVO4/Nd:YVO4 /YVO4 self-Raman laser with two Raman shifts of 816 cm-1 and 890 cm-1 [21]. Because the two first-Stokes wavelengths with Raman shifts of 816 and 890 cm-1 are too closely spaced, previous researches were mostly focused on the simultaneous multi-wavelength generation, and it’s hard to maintain the stable and efficient output performance due to the competition among multi-Stokes lines.
Passively Q-switched operation with the advantages of convenience, compactness and economical values has been recognized as a reliable approach for obtaining the short pulse width and high peak power laser [22–24]. For the typical laser crystals such as Nd:YVO4 and Nd:GdVO4, they possess the large stimulated emission cross-section at 1 µm and short fluorescence lifetime (90 µs). These characteristics depress the energy storage capability, and further limit the pulse energy and peak power. Compared with above Nd3+-doped vanadate crystals, Nd:YAP crystal has relatively smaller stimulated emission cross-section and longer fluorescence lifetime (150 µs) [25]. This means a superior energy storage capability which makes it more suitable for passively Q-switched laser operation.
In this work, the passively Q-switched YVO4 crystal Raman performances with 816 and 890 cm-1 shifts have been investigated with respective Raman configurations. Making full use of the advantages of Nd:YAP crystal and Cr4+:YAG/YAG composite crystal, efficient single first-Stokes wavelength emission with the secondary Raman shift of 816 cm-1 was obtained. The first-Stokes emission at 1184 nm and 1195 nm had been obtained in the X(YY)X (propagation direction is a-axis and polarization direction is b-axis for both pump and Stokes emissions) and X(ZZ)X (propagation direction is a-axis and polarization direction is c-axis) Raman configurations according to Porto notations in YVO4 crystal. At the absorbed pump power of 8.21 W, the respective maximum output power of 0.85 W and 0.76 W with the conversion efficiency of 10.4% and 9.3% were achieved, respectively. The passively Q-switched Raman laser output characteristics were studied and discussed.
2. Crystal chosen and experimental setup design
YVO4 as a typical Raman crystal has the tetragonal lattice structure (a = b≠c and a⊥b⊥c). This indicates that it possesses the different Raman spectra with respective polarization configurations. Though the strongest Raman shift is 890 cm-1 for different polarization configurations, however, the secondary Raman shifts are 839 cm-1 and 816 cm-1 for the Raman spectra parallel and perpendicular to the c-axis [12,16,26]. Moreover, the Raman gain of strongest and secondary Raman shifts are closer to each other for the Raman spectra perpendicular than that parallel to the c-axis. Therefore, it is easier to realize the Raman laser with the secondary Raman shift of 816 cm-1 in X(YY)X Raman configuration. Nd:YAP crystal is one of the excellent laser materials. Its strongest fundamental emission wavelength is at 1.08 µm which is longer than 1.06 µm Nd-doped fundamental laser emissions. Therefore, it should be a feasible resolution to expand Raman spectra with combining the Nd:YAP crystal and YVO4 crystal. Besides, the orthorhombic lattice structure of the crystalline host for Nd:YAP crystal makes it possesses the big natural birefringence. This characteristic is beneficial to generate the polarized laser for promoting Raman frequency conversion and realizing different polarization Raman configurations [27,28]. In our experiment, an a-cut 3 × 3 × 30 mm3 pure YVO4 crystal was used as the Raman active medium. A b-cut 0.9-at.% Nd3+-doped Nd:YAP rod crystal with Φ3.6×5.8 mm3 in size was then adopted as laser gain medium. Thus, based on the Raman shift of 890 cm-1 and 816 cm-1 in YVO4 crystal, the first-Stokes emission wavelengths at 1195 nm and 1184 nm converted from the fundamental wavelength at 1080 nm could be achieved, respectively. Their second-harmonic generation can obtain orange wavelengths between 590 and 600 nm, which are difficult to obtain by traditional solid-state lasers.
Cr4+:YAG crystal is a well-known saturable absorber and has been widely used for passively Q-switched operation for laser wavelength from 0.9 to 1.2 µm. In this experiment, a thermal diffusion bonded Cr4+:YAG/YAG composite crystal was utilized for the passively Q-switched fundamental laser operation and inserted between the Nd:YAP crystal and the YVO4 crystal. The Cr4+:YAG crystal has an initial transmittance of 85% and a size of 3 × 3 × 2 mm3. The un-doped YAG crystal with 3 × 3 × 3 mm3 in size was diffusion bonded on one surface of Cr4+:YAG crystal to enhance the heat dissipation capability. All the experimental crystals in cavity were antireflection (AR) coated at the wavelengths of the laser passing through them to reduce the intracavity loss, and tightly wrapped with indium foil and mounted in the water-cooled copper block with the temperature maintained at 20°C.
The experimental arrangement for YVO4 Raman operation intracavity driven by passively Q-switched Nd:YAP laser is shown in Fig. 1. The fundamental laser and the Raman laser shared the same simple plane-concave linear cavity formed by a pump input mirror (IM) and an output coupler (OC). The total cavity length was approximately of about 64 mm. A plane input mirror IM was high-transmission (HT, T>90%) coated at 804 nm and high-reflection (HR, R>99.9%) coated at 1000-1200 nm. The concave output mirror OC (200 mm radius of curvature) was high-reflection (HR, R>99.9%) coated at the range of 1060-1080 nm and partial-reflection (PR) coated at 1184 nm (R≈75%) and 1195 nm (R≈22%), respectively. The reflectivity at 1184 nm was much higher with compared to that at 1195 nm, so as to realize the Raman laser operation with secondary Raman shift of 816 cm-1. The passively Q-switched YVO4 crystal Raman performances with 816 and 890 cm-1 shifts have been investigated by rotating the YVO4 crystal to fit X(YY)X and X(ZZ)X Raman configurations, respectively.The cavity stability and mode radius on the center of laser crystal and Raman crystal have been calculated based on the ABCD ray transfer matrix. In this laser system, both the saturable absorber and the Raman crystal have the thermal lens effect, but we only used the equivalent lens in the middle of the laser crystal to simplify the calculation. Figure 2 shows cavity mode radius both at the center of YVO4 and Nd:YAP crystals versus thermal focal length. From the Fig. 2, the mode radius on the Nd:YAP crystal was estimated to be between 140 and 160 µm for the laser output. Therefore, the pump light was focused onto the Nd:YAP crystal with a beam spot diameter of approximately 320 µm to match the cavity mode. The pump source was a fiber (core diameter of 200 µm and numerical aperture of 0.22) coupled 804 nm laser diode and the beam was reimaged by a pair of achromatic lenses with the focal lengths of 50 and 80 mm.
Fig. 1. Experimental arrangement of the diode-end-pumped Nd:YAP/YVO4 passively Q-switched Raman laser.
3. Experiment results and discussion
Considering that the Raman spectra of YVO4 crystal was strongly depended on its Raman configurations. Therefore, the Raman laser operation for both X(ZZ)X and X(YY)X Raman configurations was investigated with setting polarization direction along c-axis and b-axis of the a-cut YVO4 crystal, respectively. The laser output spectra were measured by a grating monochromator (model Omni-λ 500 with resolution of 0.05 nm, ZOLIX) and shown in Fig. 3. In this experiment, the single Stokes wave with the center wavelength at 1183.7 nm and 1194.6 nm for the X(YY)X and X(ZZ)X Raman configurations were detected, respectively, which were converted from the same fundamental wavelength at 1079.5 nm with the Raman shifts of 816 cm-1 and 890 cm-1 of YVO4 crystal. The results show that the strongest Raman shift of 890 cm-1 was successfully suppressed for X(YY)X Raman configuration by increasing its first-Stokes wave loss.
Figure 4 shows the average output power versus the absorbed pump power for both Raman configurations, respectively. It can be seen that the Raman thresholds were very close to each other and both around 2 W in spite that the transmittances of OC at respective first-Stokes wavelengths for both Raman configurations were quite different. The threshold of first-Stokes light was very close to the threshold of fundamental light, and the output power increased rapidly with pump power as the laser emission was detected from the output coupler, which has quite a difference compared with that for the actively Q-switched operation. As we know that the Raman threshold can only be reached when the peak power of the fundamental light in the cavity accumulates to a certain value. For the acousto-optic Q-switched Raman laser, the peak power of the fundamental light increases with the pump power, and Raman threshold is also influenced by the pulse repetition frequency [2]. However, the saturable absorber can self-modulate the absorption time to generate a certain pulse peak according to power intensity in the passively Q-switched laser cavity, and the fundamental laser peak power near the threshold is similar to that at high pump power. Therefore, passively Q-switched Raman laser operation receives negligible effects from its transmittance. The average output power of both first-Stokes waves was increased with the absorbed pump power and the higher slope efficiency was obtained at a higher pump power. Because the mode radius on YVO4 became smaller with the shortening of the thermal focal length as shown in Fig. 2, the fundamental power intensity increased significantly and resulted in the improvement of Raman conversion efficiency. Consequently, under the absorbed pump power of 8.21 W, the maximum average output power of 850 mW and 760 mW for X(YY)X and X(ZZ)X Raman configurations were obtained, corresponding to the conversion efficiency of 10.4% and 9.3%, respectively. Contrary to expectations, the output power for the X(ZZ)X Raman configuration with the strongest Raman shift was relative lower compared with the X(YY)X Raman configuration with secondary Raman shift. This should mainly attribute to the much high transmission loss at 1195 nm of the output mirror. In our opinion, the output power for both configurations could be further improved by choosing the output coupler OC with more suitable transmittance at respective first-Stokes wavelength.
In the further study, the pulse behavior characteristics of two Raman configurations were investigated. The pulse trains and temporal pulse profiles for both configurations were received by an InGaAs free-space photo detector, and displayed on a 500 MHz oscilloscope (Model DPO3052B). By sharing the same saturable absorber (T0=85%), the measured pulse repetition frequency for these two Raman configurations versus the absorbed pump power were shown in Fig. 5. The pulse repetition frequency rose from 5.9 to 28.4 kHz and 3.7 to 33.5 kHz with the incident pump power increased from the thresholds, respectively. The pulse repetition frequencies of 28.4 and 33.5 kHz were obtained at the absorbed pump power of 8.21 W for X(YY)X and X(ZZ)X Raman configurations. The pulse repetition frequency of the passively Q-switched Raman laser was mainly attributed to the loss modulation of the fundamental wave. Raman conversion efficiency leaded to different loss of fundamental wave for both Raman configurations in this experiment. Therefore, the X(ZZ)X Raman configuration with slightly lower conversion efficiency for 1194.6 nm generation resulted in higher pulse repetition frequency with comparing to the X(YY)X Raman configuration for 1183.7 nm generation.
Fig. 5. Pulse repetition frequency (PRF) versus absorbed pump power for X(YY)X and X(ZZ)X configurations. (Inserts show the pulse trains under the maximum output power for two Raman configurations.)
Figure 6 shows the pulse width of the first-Stokes waves for X(YY)X and X(ZZ)X Raman configurations which were fluctuated among 3.5-4.3 ns and 1.5-2.2 ns, respectively. Under an absorbed pump power of 8.21 W, the pulse widths was about 3.5 ns and 1.5 ns for these two cases and the temporal pulse profiles were exhibited in Fig. 6. In comparison, the pulse width of the X(ZZ)X Raman configuration was much narrower than that of X(YY)X Raman configuration. This is mainly determined by the Raman gain of both Raman shifts and the transmission loss of the output coupler at both first-Stokes wavelengths. The corresponding pulse energy and peak power were calculated as 29.9 µJ and 8.6 kW for 1184 nm Raman emission, 22.7 µJ and 15.1 kW for 1195 nm Raman emission, respectively. The marked difference in peak power for both first-Stokes waves also resulted in the noise intensity of pulse profiles for X(YY)X Raman configuration was much larger than X(ZZ)X Raman configuration as shown in Fig. 4 and Fig. 7.
Fig. 7. Temporal pulse profiles of Raman laser for X(YY)X and X(ZZ)X configurations at absorbed pump power of 8.21 W.
4. Conclusion
In conclusion, by employing a Cr4+:YAG/YAG composite crystal with an initial transmittance of 85% as a saturable absorber, the passively Q-switched Nd:YAP/YVO4 Raman laser has been demonstrated. The Raman performance of the a-cut YVO4 crystal with two different Raman configurations was investigated, respectively. The efficient first-stokes wavelengths at 1183.7 nm and 1194.6 nm were realized with the Raman shifts of 816 and 890 cm-1 from X(YY)X and X(ZZ)X configurations, respectively. Under an absorbed pump power of 8.21 W, the maximum output power of 0.85 W and 0.76 W with the conversion efficiency of 10.4% and 9.3% were obtained. The corresponded pulse widths were 3.5 ns and 1.5 ns with the pulse repetition frequency of both approximately of 30 kHz. Therefore, the single pulse energy and the peak power were calculated as 29.9 µJ and 8.6 kW for 1184 nm Raman emission, 22.7 µJ and 15.1 kW for 1195 nm Raman emission, respectively. These passively Q-switched Raman laser output characteristics were investigated and shown some interesting results. Experimental results show that the threshold of first-Stokes wave was almost negligible on the effect of the transmittance and was very close to the threshold of its fundamental wave. This special threshold characteristic was attributed to the self-modulate pulse mechanism for the passively Q-switch operation, which was quite different with that for the actively Q-switching operation. The pulse repetition frequency of the passively Q-switched Raman laser was mainly attributed to the loss modulation of the fundamental wave induced by Raman conversion. These laser output characteristics may have some reference value for Raman laser design.
Funding
Public welfare projects of Wenzhou city (G2020013, S20180015); Natural Science Foundation of Zhejiang Province (LY19F050012); National Natural Science Foundation of China (61905180, 62075167).
Disclosures
The authors declare no conflicts of interest.
Data availability
No data were generated or analyzed in the presented research.
References
1. H. M. Pask, P. Dekker, R. P. Mildren, D. J. Spence, and J. A. Piper, “Wavelength-versatile visible and UV sources based on crystalline Raman lasers,” Prog. Quantum Electron. 32(3-4), 121–158 (2008). [CrossRef]
2. Y. M. Duan, H. Y. Zhu, Y. J. Zhang, G. Zhang, J. Zhang, D. Y. Tang, and A. A. Kaminskii, “RbTiOPO4 cascaded Raman operation with multiple Raman frequency shifts derived by Q-switched Nd:YAlO3 laser,” Sci. Rep. 6(1), 33852 (2016). [CrossRef]
3. E. Perez, U. Sheintop, R. Nahear, G. Marcus, and S. Noach, “Efficient all-solid-state passively Q-switched SWIR Tm:YAP/KGW Raman laser,” Opt. Lett. 45(19), 5409–5412 (2020). [CrossRef]
4. X. H. Gong, H. Y. Zhu, Y. J. Chen, J. H. Huang, Y. F. Lin, Z. D. Luo, and Y. D. Huang, “Nd3+ cluster adjustment in Nd3+:CaNb2O6 by codoping La3+ buffers for improvement of fundamental and self-stimulated Raman scattering laser operation: a study case from the perspective of defect chemistry,” Cryst. Growth Des. 19(12), 6963–6971 (2019). [CrossRef]
5. F. L. Gao, X. Y. Zhang, Z. H. Cong, Z. J. Liu, X. H. Chen, Z. G. Qin, P. Wang, and J. J. Xu, “Tunable Stokes laser based on the cascaded stimulated polariton scattering and stimulated Raman scattering in RbTiOPO4 crystal,” Opt. Lett. 45(4), 861–864 (2020). [CrossRef]
6. M. Y. Cheng, Y. M. Duan, Y. L. Sun, L. Zhang, and H. Y. Zhu, “Research progress of Raman and frequency mixing for visible lasers based on vanadate crystals,” Laser and Optoelectronics Prog. 57(7), 071611 (2020). [CrossRef]
7. H. Zhao, Z. H. Tu, S. B. Dai, S. Q. Zhu, H. Yin, Z. Li, and Z. Q. Chen, “Single-longitudinal-mode cascaded crystalline Raman laser at 1.7 µm,” Opt. Lett. 45(24), 6715–6718 (2020). [CrossRef]
8. Y. M. Duan, Y. L. Sun, H. Y. Zhu, T. W. Mao, L. Zhang, and X. Chen, “YVO4 cascaded Raman laser for five-visible-wavelength switchable emission,” Opt. Lett. 45(9), 2564–2567 (2020). [CrossRef]
9. Y. C. Liu, C. M. Chen, J. Q. Hsiao, Y. Y. Pan, C. H. Tsou, H. C. Liang, and Y. F. Chen, “Compact efficient high-power triple-color Nd:YVO4 yellow-lime-green self-Raman lasers,” Opt. Lett. 45(5), 1144–1147 (2020). [CrossRef]
10. A. A. Kaminskii, K. I. Ueda, H. J. Eichler, Y. Kuwano, H. Kouta, S. N. Bagaev, T. H. Chyba, J. C. Barnes, G. M. Gad, and T. Murai, “Tetragonal vanadates YVO4 and GdVO4-new efficient χ(3)-materials for Raman lasers,” Opt. Commun. 194(1-3), 201–206 (2001). [CrossRef]
11. Z. Xie, Y. M. Duan, J. H. Guo, X. H. Huang, L. H. Yan, and H. Y. Zhu, “Cascaded a-cut NdYVO4 self-Raman with second-Stokes laser at 1313 nm,” J. Opt. 19(11), 115501 (2017). [CrossRef]
12. H. Y. Zhu, J. H. Guo, X. K. Ruan, C. W. Xu, Y. M. Duan, Y. J. Zhang, and D. Y. Tang, “Cascaded self-Raman laser emitting around 1.2-1.3 µm based on a c-cut Nd:YVO4 crystal,” IEEE Photonics J. 20(14), 15180 (2012). [CrossRef]
13. X. H. Che, J. Xu, H. D. Li, and S. H. Ding, “Analysis of actively Q-switched infrared Raman lasers with crystalline media of multi-Raman-modes,” Infrared Phys. Technol. 111, 103474 (2020). [CrossRef]
14. J. H. Guo, H. Y. Zhu, Y. M. Duan, C. W. Xu, X. K. Ruan, G. H. Cui, and L. F. Yan, “Cascaded c-cut Nd:YVO4 self-Raman laser operation with a single 259 cm−1 shift,” J. Opt. 19(3), 035501 (2017). [CrossRef]
15. J. Dong, X. L. Wang, M. M. Zhang, X. J. Wang, and H. S. He, “Structured optical vortices with broadband comb-like optical spectra in Yb:Y3Al5O12/YVO4 Raman microchip laser,” Appl. Phys. Lett. 112(16), 161108 (2018). [CrossRef]
16. R. Li, R. Bauer, and W. Lubeigt, “Continuous-Wave Nd:YVO4 self-Raman lasers operating at 1109 nm, 1158 nm and 1231 nm,” Opt. Express 21(15), 17745–17750 (2013). [CrossRef]
17. H. Y. Lin, X. H. Huang, S. Dong, and X. Liu, “Passively Q-switched multi-wavelength Nd:YVO4 self-Raman laser,” J. Mod. Opt. 63(21), 2235–2237 (2016). [CrossRef]
18. H. Y. Lin, X. Pan, X. H. Huang, M. Xiao, Y. C. Xu, and W. Z. Zhu, “Cr4+:YAG passively Q-switched c-cut Nd:YVO4 self-Raman laser at 1168.6 nm,” Infrared Phys. Technol. 75, 56–58 (2016). [CrossRef]
19. X. J. Wang, X. L. Wang, Z. F. Zheng, X. H. Qiao, and J. Dong, “2018.4 nm and 1174.7 nm dual-wavelength Nd:GdVO4/Cr4+:YAG/YVO4 passively Q-switched Raman microchip laser,” Appl. Opt. 57(12), 3198–3204 (2018). [CrossRef]
20. L. J. Wei, M. T. Chen, S. Q. Zhu, S. B. Dai, H. Yin, and Z. Q. Chen, “A passively Q-switched YVO4 Raman laser with orthogonally polarized emission at 1175.4 nm and 1165.2 nm,” Laser Phys. Lett. 15(12), 125001 (2018). [CrossRef]
21. L. Fan, X. D. Zhao, Y. C. Zhang, X. D. Gu, H. P. Wan, H. B. Fan, and J. Zhu, “Multi-wavelength continuous-wave Nd:YVO4 self-Raman laser under in-band pumping,” Chin. Phys. B 28(8), 084210 (2019). [CrossRef]
22. Y. M. Duan, J. Zhang, H. Y. Zhu, Y. C. Zhang, C. W. Xu, H. Y. Wang, and D. Y. Fan, “Compact passively Q-switched RbTiOPO4 cascaded Raman operation,” Opt. Lett. 43(19), 4550–4553 (2018). [CrossRef]
23. W. Jiang, Z. Li, S. Q. Zhu, H. Yin, Z. Q. Chen, G. Zhang, and W. D. Chen, “YVO4 Raman laser pumped by a passively Q-switched Yb:YAG laser,” Opt. Express 25(13), 14033–14042 (2017). [CrossRef]
24. L. Zhang, Y. M. Duan, Y. L. Sun, Y. J. Chen, Z. H. Li, H. Y. Zhu, G. Zhang, and D. Y. Tang, “Passively Q-switched multiple visible wavelengths switchable YVO4 Raman laser,” J. Lumin. 228, 117650 (2020). [CrossRef]
25. H. Y. Shen, R. R. Zeng, Y. P. Zhou, G. F. Yu, C. H. Huang, Z. D. Zeng, W. J. Zhang, and Q. J. Ye, “Comparison of simultaneous multiple wavelength lasing in various neodymium host crystals at transitions from 4F3/2-4I11/2 and 4F3/2-4I13/2,” Appl. Phys. Lett. 56(20), 1937–1938 (1990). [CrossRef]
26. A. A. Kaminskii, H. J. Eichler, H. Rhee, K. Ueda, K. Oka, and H. Shibata, “New manifestations of nonlinear χ(3)-laser properties in tetragonal YVO4 crystal: many-phonon SRS, cascaded self-frequency “tripling”, and self-sum-frequency generation in blue spectral range with the involving of Stokes components under one-micron picosecond pumping,” Laser Phys. Lett. 5(11), 804–811 (2008). [CrossRef]
27. H. Y. Zhu, Y. M. Duan, H. Y. Wang, Z. H. Shao, Y. J. Zhang, G. Zhang, J. Zhang, and D. Y. Tang, “Compact Nd:YAlO3/RbTiOPO4 based intra-cavity optical parametric oscillator emit at 1.65 and 3.13 µm,” IEEE. J. Sel. Top. Quant. 21(1), 1600105 (2015).
28. S. M. Chen, M. Y. Cheng, H. Y. Zhu, T. W. Mao, X. M. Zhang, Q. Q. Zhou, G. Zhang, and Y. M. Duan, “Orange, yellow and green emissions generated in Q-switched Nd:YALO3/YVO4 Raman laser,” J. Lumin. 214, 116555 (2019). [CrossRef]
