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Accepted papers to appear in an upcoming issue

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Localized cavity loss induced external mode coupling in optical microresonators

Yong-Zhen Huang, Yue-De Yang, Bowen Liu, Jin-Long Xiao, and Hai-Zhong Weng

Doc ID: 242013 Received 29 May 2015; Accepted 02 Oct 2015; Posted 02 Oct 2015  View: PDF

Abstract: We study the external mode coupling in optical microresonators with a loss dependent coupling coefficient. In the case of dielectric optical microresonators with localized absorption or radiation loss, the mode coupling between whispering-gallery modes can result in a destructive interference of the mode fields in the lossy area and consequently reduce the mode loss. Once the reduction overcomes the introduced loss, the actual mode loss is reduced by increasing the loss factor. An anomalous relation between the actual mode loss and introduced loss factor is then found, while the mode frequencies show a parallel, crossing, or anti-crossing behavior under different coupling conditions, such phenomena can be well explained by the analysis based on the coupling theory. The results show that the variable localized cavity loss can suppress the original whispering-gallery modes and generate high-Q coupled modes, which illustrate a possible way to dynamically control the optical modes inside microresonator.

Ultra-broadband mid-infrared supercontinuum generation through dispersion engineering of chalcogenide microstructured fibers

Mohammad Rezaul Karim, Azizur Rahman, Yousaf Azabi, Arti Agrawal, and Govind Agrawal

Doc ID: 246152 Received 17 Jul 2015; Accepted 02 Oct 2015; Posted 02 Oct 2015  View: PDF

Abstract: We demonstrate numerically that the use of dispersion-engineered microstrucured fibers made with chalcogenide glasses allows one to generate ultra-broadband supercontinuum spectra in the mid-infrared region by launching optical pulses at a suitable wavelength. As a specific example, numerical simulations show that such a 1-cm-long fiber, made with Ge₁₁.₅As₂₄Se₆₄.₅ glass and pumped at a wavelength of 3.1 μm using short pulses with a relatively modest peak power of 3 kW, can produce a spectrum extending from 1.3 μm to beyond 11 μm (more than 3 octaves). We consider three fiber structures with microstrucured air holes in their cladding and find their optimum designs through dispersion engineering. Among these, equiangular-spiral microstrucured fiber is found to be the most promising candidate for generating ultrawide supercontinuum in the mid-infrared region.

All-optical switching of nonlinear hyperbolic metamaterials in visible and near-infrared regions

Mohammad Moravvej-Farshi, Maziar Shoaei, and Leila Yousefi

Doc ID: 246198 Received 24 Jul 2015; Accepted 30 Sep 2015; Posted 01 Oct 2015  View: PDF

Abstract: Taking advantage of the Kerr nonlinearities of metallic nanolayers and graphene (G) and the well-known pump-probe method, we show that 200-nm wide slabs of hyperbolic metamaterial (HMM) composed of fourteen vertically stacked unit cells can be switched all optically between negative refraction regime (ON state) and no transmission regime (OFF state), when illuminated by appropriately chosen TE polarized Gaussian pump and TM polarized CW probe. Finite element method (FEM) numerical simulations show that the HMM slab with unit cells made of Au/Al2O3 nanolayers suffering from a relatively large plasmonic loss exhibits an ON state transmittance spectrum limited to 52%-72% over the visible range of 585-600 nm, when a 500 V/μm pump signal is utilized. Similar numerical results obtained for the HMM slab whose unit cells are made of Au/Al₂O₃/G/Al₂O₃/Au nanolayers show that a 4 V/μm pump signal is enough to stimulate the Kerr effect, resulting in a ~97% ON state transmittance over the ultra-narrow band of 803-805 nm. Moreover, simulations show that when the unit cells are made of Ag/Si/G/Si/Ag nanolayers a 95-nm wide ON state transmittance of 49%-99% over the IR range of 800-895 nm can be obtained with a 19.5 V/μm pump. The proposed HMM structures can be used as all-optical switches in future optical digital systems.

Modeling the resonance focusing of a picosecond laser pulse using a dielectric microcylinder

Elena Kozlova, Victor Kotlyar, and Sergey Degtyarev

Doc ID: 243740 Received 25 Jun 2015; Accepted 30 Sep 2015; Posted 01 Oct 2015  View: PDF

Abstract: Based on the FDTD method, we study temporal variations of the focal spot parameters when focusing a plane ТЕ-wave by a dielectric microcylinder with refractive index 1.59. It is shown that as a ps-pulse travels through the microcylinder, the focal spot gets tighter, whereas its intensity and the mode energy stored in the microcylinder grow. As a result of the ps-pulse passage, in the cylinder a whispering gallery mode (WGM) is excited, which is coincident with the mode in a circular wire with zero propagation constant. With time, the mode energy is leaking out. By solving the Helmholtz equation using a finite-element technique we show that in the stationary case, the best focal spot parameters are achieved in a cylinder of radius 2.1749λ (λ is wavelength): the focal spot size is FWHM = 0.226λ, whereas the maximal intensity in the focus is 60 times the incident light intensity.

Investigations of Influences of Spontaneous Emission Properties on Surface Plasmon Polariton Amplifications with the Rate-equation Theory

Qinghe Mao, Bo Yao, and Ye Liu

Doc ID: 247331 Received 04 Aug 2015; Accepted 28 Sep 2015; Posted 01 Oct 2015  View: PDF

Abstract: The inluences of the position-related spontaneous emission properties of gain media on gain and ASE noise characteristics of SPP amplification are investigated with rate-equation theory in this paper. It is found that both the spontaneous emission rate and the probability of spontaneous emission into the SPP mode of the gain media in SPP waveguide are position-related. Based on this, a rate-equation model considering those spontaneous emission properties is presented. With this model, the influences of the position-related spontaneous emission properties on the gain and ASE noise characteristics of single-mode DLSPP amplifier are discussed. The results show that the spontaneous emission rate of gain media is enhanced near the metal interface and the probability of spontaneous emission into SPP mode decreases near both the metal and air interfaces of the amplifier. This gives rise to reduced gain and low ASE output power. Moreover, the noise property of the amplifier may be improved because of the great decrease in the output ASE power.

65-fs Yb:CaF₂ laser mode-locked by SESAM

Federico Pirzio, Samuele Di Dio Cafiso, matthias kemnitzer, Florian Kienle, Annalisa Guandalini, Juerg Aus der Au, and Antonio Agnesi

Doc ID: 247178 Received 03 Aug 2015; Accepted 25 Sep 2015; Posted 25 Sep 2015  View: PDF

Abstract: An Yb:CaF₂ laser pumped by two 400-mW single-mode laser diodes at 976 nm is reported to generate Fourier-limited 65-fs pulses, the shortest to date achieved with SESAM mode-locking and this laser material to date. With a multimode pump diode we have demonstrated higher average output powers of up to 1.4 W with 87-fs pulses. Key to these successful results was the implementation of practical design guidelines allowing safe mode-locking operation without Q-switching instabilities which appear to damage the SESAMs more easily in Yb:CaF₂ oscillators compared to other Yb-doped materials.

Improving entanglement of even entangled coherent states by a coherent superposition of photon subtraction and addition

Li-yun Hu, Jiani Wu, Shi-You Liu, Jiehui Huang, zhenglu duan, and Yinghua Ji

Doc ID: 247009 Received 29 Jul 2015; Accepted 20 Sep 2015; Posted 22 Sep 2015  View: PDF

Abstract: A new entangled quantum state is introduced by applying local coherent superposition (CS) (ra^{†}+ta) of photon subtraction and addition to each mode of even entangled coherent state (EECS) and the properties of entanglement are investigated in terms of EPR correlation, the degree of entanglement and the average fidelity of quantum teleportation. It is found that the single- and two-mode CS operations can improve the EPR correlation of the EECS in a big and small region of amplitude, respectively, and the enhanced entanglement and fidelity depend on the even or odd order of CS. All optimal results are not achieved at two extreme cases of t=0,1.

Analyzing bull's eye structures by a vertical mode expansion method with rotational symmetry

Ya Yan Lu and Xun Lu

Doc ID: 243490 Received 22 Jun 2015; Accepted 19 Sep 2015; Posted 23 Sep 2015  View: PDF

Abstract: A bull's eye structure is a metallic film with a circular subwavelength aperture surrounded by concentric annular grooves. It is an important structure for realizing applications of the extraordinary optical transmission phenomenon. The structure is invariant under rotations about the central axis perpendicular to the film. In this paper, an efficient numerical method is developed for analyzing bull's eye and other structures that consist of different annular regions where the material properties are one-dimensional. The method is a new variant of of the recently developed vertical mode expansion method (VMEM) which combines field expansions in one-dimensional eigenmodes with various techniques for solving scalar two-dimensional Helmholtz equations. The method exploits the rotational symmetry by solving the different Fourier components separately. For normal incident waves, the method is particularly efficient, since it is only necessary to solve one Fourier mode. The method is used to analyze bull's eye structures with different configurations. In particular, we found that the normalized transmission coefficient can be larger than 52 for a bull's eye structure with 22 grooves.

Goos-Hänchen shift of the reflected beam in a standing-wave coupled electromagnetically induced transparency system

XiaoJun Zhang, Haihua Wang, ChunLiang Wang, Yan Xu, Zhi-Peng Liang, Cun-Bo Fan, Cheng-Zhi Liu, and Jin-Yue Gao

Doc ID: 242196 Received 03 Jun 2015; Accepted 15 Sep 2015; Posted 17 Sep 2015  View: PDF

Abstract: The Goos-Hänchen shift of the reflected beam in a standing-wave coupled electromagnetically induced transparency media is investigated. We adopt the three-level $\Lambda$ system as a model of $^{87}$Rb atomic media. Under the influence of two counter-propagating coupling fields, the incident beam is converted into a reflected one, with the Goos-H\"{a}nchen shift. We briefly discussed the rules of obtaining the efficient reflection in such atomic system, and carefully investigated the Goos-H\"{a}nchen shift and its dependence on beam width of the incident field. Both the cases with and without Doppler broadenings are considered. In order to provide more clear physics on the large shift that could be realized, The concept of penetration depth is used to analyze the shift phenomenologically.

Effect of Symmetry in Periodic Nanostructures on Light-Trapping in Thin Film Solar Cells

Sang Eon Han and Tianhao Cai

Doc ID: 242380 Received 05 Jun 2015; Accepted 14 Sep 2015; Posted 15 Sep 2015  View: PDF

Abstract: We perform detailed theoretical analysis on the relation between the symmetry in periodic nanostructures and its light-trapping performance in thin film photovoltaics. It has been believed that the increase in the number of resonances by symmetry-breaking enhances broad band absorption. However, our calculations show that this belief is not strictly true. We find that the correlation between the number of resonances and the spectral average absorption is only rough. By breaking the symmetry systematically, we identify the symmetry-breaking steps that significantly enhance broad band absorption. Our results show that these symmetry-breaking steps do not always agree with the steps that increase the number of resonances. However, both the level of absorptance and the number of resonances in general increase by symmetry-breaking, which is in agreement with previously reported results. Because group theory is related only to the number of resonances, our results suggest that the symmetry in light-trapping nanostructures should not be chosen solely based on simple group theory analysis.

Point source generation of chiral fields: Measures of near- and far-field optical helicity

David Andrews, Jamie Leeder, and Henryk Haniewicz

Doc ID: 240189 Received 01 May 2015; Accepted 11 Sep 2015; Posted 01 Oct 2015  View: PDF

Abstract: To consider the relationship between different measures of chirality in an optical field, the simplest case is considered: direct spontaneous emission of circularly polarized light by a point source. In the electromagnetic fields radiated from a suitably chiral source, such as a low-symmetry chiral molecule undergoing radiative decay, optical helicity is exhibited in the extent of a difference in left- and right-handed circular polarization components. There are several practical measures for quantifying the emergence of ensuing optical helicity, exhibiting different forms of dependence on the properties of the emitter and the positioning of a detector. By casting each measure in terms of an irreducible helicity density, connections and distinctions can be drawn between results expressible in either classical or quantum form.

Multi-pulse storage and manipulation via solitonic solutions

Rodrigo Gutiérrez-Cuevas and Joseph Eberly

Doc ID: 244030 Received 01 Jul 2015; Accepted 10 Sep 2015; Posted 10 Sep 2015  View: PDF

Abstract: Solutions to the Maxwell-Bloch equations for a Λ-system are computed using the single-soliton Darboux transformation and the nonlinear superposition principle. These allow complete control of information deposited by a signal pulse (with the help of an auxiliary control pulse) in the coherence of the medium’s ground states by injecting sub-sequential pulses. Additionally, we study the encoding of two signal pulses and their manipulation by a control pulse and show that multi-pulse storage and control are possible as long as the imprints made by encoding the signal pulses are sufficiently separated.

Polycrystalline Anatase Titanium Dioxide Micro-ring Resonators with Negative Thermo-optic Coefficient

Orad Reshef, Katia Shtyrkova, Michael Moebius, Sarah Griesse-Nascimento, Steven Spector, Christopher Evans, Erich Ippen, and Eric Mazur

Doc ID: 245825 Received 13 Jul 2015; Accepted 06 Sep 2015; Posted 18 Sep 2015  View: PDF

Abstract: We fabricate polycrystalline anatase TiO2 micro-ring resonators with intrinsic Q-factors as high as 51,000 and losses as low as 0.70 dB/mm at λ = 1574 nm. Additionally, we measure a negative thermo-optic coefficient (dn/dT) of –4.9 ± 0.5 × 10–5 K–1. The presented fabrication uses CMOS-compatible lithographic techniques that take advantage of substrate-independent, non-epitaxial growth. These properties make polycrystalline anatase a promising candidate for the implementation of athermal, vertically-integrated, CMOS-compatible nanophotonic devices with nonlinear applications.

High-power pulse trains excited by modulated continuous waves

Wang yan, Lijun Song, Boris Malomed, and Li Lu

Doc ID: 243078 Received 17 Jun 2015; Accepted 05 Sep 2015; Posted 08 Sep 2015  View: PDF

Abstract: High-power pulse trains growing from modulated continuous waves (CWs) are considered, using solutions of the Hirota equation for solitons on a finite background. The results demonstrate that pulses extracted from the maximally compressed trains can propagate preserving their shape and forming bound states. The dynamics of double high-power pulse trains produced by modulated CWs in a model of optical fibers is considered in detail too. It is demonstrated that the double trains propagate in a robust form, with frequencies shifted by the Raman effect.

Dressed lifetime of fourth-order fluorescence and spontaneous parametric four-wave mixing in Pr3+:YSO

Yanpeng Zhang, Changbiao Li, Hua Zhong, Shi Li, Zihai Jiang, Tao Jiang, and Feng Ma

Doc ID: 244193 Received 02 Jul 2015; Accepted 02 Sep 2015; Posted 08 Sep 2015  View: PDF

Abstract: We report the measured dressed lifetimes of fourth-order fluorescence and spontaneous parametric four-wave mixing (SP-FWM) signals by the method of the perturbation chain in two-level and a heteronuclear-like molecule system of Pr3+:YSO both in theory and experiment. The lifetime of fourth-order fluorescence depend on the nonlinear processes in perturbation chain, and can be modulated by the dark state due to the dressing effect and the induced dipole-dipole interaction by changing the frequency detuning and power of the controlling field. Such results can find potential applications in all-optical communication and optical information processing on photonic chip.

Practical long-distance quantum key distribution through concatenated entanglement swapping with parametric down-conversion sources

Aeysha Khalique and Barry Sanders

Doc ID: 242053 Received 29 May 2015; Accepted 01 Sep 2015; Posted 01 Oct 2015  View: PDF

Abstract: We develop a theory for long-distance quantum key distribution based on concatenated entanglement swapping using parametric down-conversion sources and show numerical results of our model. The model incorporates practical resources including multi-pair sources, inefficient detectors with dark counts and lossy channels. We calculate the maximum secret key-generation rate for up to three entanglement swapping stations by optimizing over resource parameters, and our numerical simulation shows that the range of quantum key distribution can in principle be markedly increased but at the expense of an atrociously unfeasible secret key-generation rate; however, the upper bound of our key rates closely approach the Takeoka-Guha-Wilde upper bound. Our analysis demonstrates the need for new technology such as quantum memory to synchronize photons and our methods should serve as a valuable component for accurately modelling quantum-memory-based long-distance quantum key distribution.

Holographic recording of integrated optics using photo-modification of semiconductor materials

Sergei Krivoshlykov

Doc ID: 245390 Received 06 Jul 2015; Accepted 22 Aug 2015; Posted 01 Oct 2015  View: PDF

Abstract: Holographic recording of the relief-free diffraction gratings and channel waveguides with large refractive index contrast of 0.8-1.2 is demonstrated employing photo-modification of GaAs semiconductor material under illumination with low intensity light. The developed technology opens door to direct optical recording and high-density monolithic integration of integrated optical components based on such compound semiconductor materials as GaAs and InP.

Saturable and inverse saturable absorption in multi-walled-carbon-nano-tubes-doped fast Sol-gel hybrid glasses

Raphi Dror, ZeeV Burshtein, Raz Gvishi, and Mariana Pokrass

Doc ID: 232480 Received 14 Jan 2015; Accepted 10 Apr 2015; Posted 10 Apr 2015  View: PDF

Abstract: Dynamics of saturable absorption and inverse saturable absorption of Multi walled carbon nano tubes (MWCNT)-doped fast Sol-gel hybrid glasses was studied by optical transmission of 532-nm laser beam pulses at two extreme conditions: 6-ns long temporally isolated single pulses up to 0.02 J/cm2, and a pulse train at different intensities in the range 0.72-10.7 kW/cm2 (quasi-CW illumination). The temporally isolated single pulses were analysed by the slow saturable absorber limit; The quasi-CW illumination at steady state was analysed by the fast inverse saturable absorber limit. A fresh, corrected solution to the rate equation was developed for the latter. The time dependence of reaching steady state absorption in the quasi-CW case was analysed by a numerical simulation of a state model. The single-pulse case analysis yields a ground-state density N=5.1×1015cm-3, a ground-state absorption cross-section σgs=5.5×10-15cm2 , and a first excited-state absorption cross-section σes1=3.6×10-15cm2. The quasi-CW case analysis is consistent with the occurrence of the MWCNT transition upon illumination into a highly absorbing/scattering state ("plasma" state). The analysis yields a ground-state concentration estimation N=3.2×1015cm-3, and a ground-state absorption cross-section σgs=6.3×10-15cm2. The "plasma" lower-state absorption/ scattering cross-section is σes2=2.3×10-14cm2. The light-intensity dependent transition rate between the first MWCNT excited-state and its "plasma" lower state followed the relation τ-1inc[s-1]=12.25exp(4×10-7I[W/cm2]); the transition rate between the lowest "plasma" state and the MWCNT ground-state, was also light-intensity dependent, following the relation τ-1[s-1]=3.5exp(2.54×10-7I[W/cm2]).

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