Accepted papers to appear in an upcoming issue
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Mode splitting super-resolved by Fano interference
Yue Wang, Hongchun Zhao, Yancheng Li, Fengfeng Shu, Mingbo Chi, Yang Xu, and Yihui Wu
Doc ID: 360244 Received 15 Feb 2019; Accepted 20 Mar 2019; Posted 20 Mar 2019 View: PDF
Abstract: Optical whispering gallery mode (WGM) resonator supports degeneracy of counter-propagating modes. Rayleigh scattering can lift it as mode splitting, the spectral response of which facilities quantitative analysis of the scatter. However, it becomes hard if the scattering is weak. Here we develop a spectroscopical method of identifying arbitrary small mode splitting using Fano interference induced spectral response modification. Scattering information can be revealed by fitting the responses as a function of field’s phase and intensity. Besides, we show that this modified response helps achieve ultralow detection limit for mode splitting based nanoparticle detection. This approach may find promising applications in high Q-factor devices characterization, novel sensing method exploration, mode identification in coupled photonic system and quantum weakly coupling system investigation.
Nonreciprocal unconventional photon blockade
Baijun Li, Ran Huang, xun wei xu, Adam Miranowicz, and Hui Jing
Doc ID: 359390 Received 01 Feb 2019; Accepted 19 Mar 2019; Posted 20 Mar 2019 View: PDF
Abstract: We propose how to achieve quantum nonreciprocity via unconventionalphoton blockade (UPB) in a compound device consisting of anoptical harmonic resonator and a spinning optomechanicalresonator. We show that, even with a very weak single-photonnonlinearity, nonreciprocal UPB can emerge in this system, i.e.,strong photon antibunching can emerge only by driving the devicefrom one side, but not from the other side. This nonreciprocity results from theFizeau drag, leading to different splitting of the resonance frequencies forthe optical counter-circulating modes. Such quantum nonreciprocal devices can be particularly useful in achieving back-action-free quantum sensing or chiral photonic communications.
Ultra-high resolution detection of Pb2+ Ions using a Black Phosphorus Functionalized Microfibre Coil Resonator
Yu Yin, Shi Li, Shunbin Wang, Shijie Jia, Jing Ren, Gerald Farrell, Elfed Lewis, and Pengfei Wang
Doc ID: 362167 Received 12 Mar 2019; Accepted 17 Mar 2019; Posted 18 Mar 2019 View: PDF
Abstract: A black phosphorus (BP) functionalized optical fibre sensor based on a microfibre coil resonator (MCR) for Pb2+ ions detection in an aquatic environment is presented and experimentally demonstrated. The MCR-BP sensor is manufactured by winding a tapered microfibre on a hollow rod composed of a low refractive index PC resin with the BP deposited on the internal wall of the rod. Based on the propagation properties of the MCR, the chemical interaction between the Pb2+ ions and the BP alters the refractive index of the ambient environment and thus results in a detectable shift in the transmission spectrum. The resonance wavelength moves towards longer wavelengths with an increasing concentration of Pb2+ ions and the sensor has an ultra-high detection resolution of 0.0285 ppb. The temperature dependence is 106.95 pm/oC due to the strong thermo-optic and thermal-expansion effect of the low refractive index PC resin. In addition, the sensor shows good stability over a period of 15 days. The local pH also influences the sensor, with the resonance wavelength shift increasing as pH approaches a value of 7 but then decreasing as the pH value increases further due to the effect of the BP layer by H+ and OH- ions. The sensor shows the potential for high resolution detection of Pb2+ ions in a liquid environment with the particular advantages of having a simple structure, ease of fabrication, low cost, low loss and simple interrogation.
Whispering-gallery mode hexagonal micro/nano-cavity lasers
Yue-De Yang, Min Tang, Fu-Li Wang, Zhi-Xiong Xiao, Jin-Long Xiao, and Yong-Zhen Huang
Doc ID: 359279 Received 31 Jan 2019; Accepted 14 Mar 2019; Posted 14 Mar 2019 View: PDF
Abstract: Whispering-gallery mode (WGM) hexagonal optical micro/nano-cavities can be utilized as high quality (Q) resonators for realizing compact-size low-threshold lasers. In this paper, we review the progress in WGM hexagonal micro/nano-cavity lasers comprehensively. The high-Q WGMs in hexagonal cavities are divided into two kinds of resonances propagating along the hexagonal and triangular periodic orbits with distinct mode characteristics according to the theoretical analyses and numerical simulations, while the WGMs in wavelength-scale nanocavity cannot be well described by the ray model. The hexagonal micro/nano-cavity lasers can be made by both bottom-up and top-down processes leading to the diversity of these lasers. The ZnO- or nitride-based semiconductor material generally has a wurtzite crystal structure and typically presents a natural hexagonal cross section. The bottom-up growth guarantees smooth surface faceting and hence reduces the scattering loss effectively. Laser emissions have been successfully demonstrated in the synthesized hexagonal micro/nano-cavities with various materials and structures. Furthermore, slight deformation can be easily introduced and precisely controlled in the top-down fabrication, which allows the manipulation of lasing modes. WGM lasing with excellent single-transverse-mode property was realized in waveguide-coupled ideal and deformed hexagonal microcavity lasers.
Visible Kerr comb generation in a high-Q silica microdisk resonator with a large wedge angle
Jiyang Ma, Longfu Xiao, Jiaxi Gu, Hao Li, Xinyu Cheng, Guangqiang He, Xiaoshun Jiang, and Min Xiao
Doc ID: 356704 Received 04 Jan 2019; Accepted 14 Mar 2019; Posted 14 Mar 2019 View: PDF
Abstract: This paper describes the specially designed geometry of a dry-etched large-wedge-angle silica microdisk resonator that enables anomalous dispersion in the 780 nm wavelength regime. This anomalous dispersion occurs naturally without the use of mode-hybridization technique to control the geometrical dispersion. By fabricating a 1 μm-thick silica microdisk with a wedge angle as large as 56 degree and optical Q-factor larger than 107, we achieve a visible Kerr comb that covers the wavelength interval of 700–897 nm. The wide optical frequency range and the closeness to the clock transition at 698 nm of 87Sr atoms makes our visible comb a potentially useful tool in optical atomic clock applications.
Dual-band and ultra-broadband photonic spin-orbit interaction for electromagnetic shaping based on single-layer silicon metasurfaces
Xin Xie, Mingbo Pu, xiong li, kaipeng Liu, Jinjin Jin, Xiaoliang Ma, and Xiangang Luo
Doc ID: 357743 Received 15 Jan 2019; Accepted 13 Mar 2019; Posted 14 Mar 2019 View: PDF
Abstract: Achieving electromagnetic wave scattering manipulation in multi-spectral and broad operation band is a long pursuit in stealth applications. Here, we present an approach by using single-layer metasurfaces composed of space-variant amorphous silicon ridges tiled on a metallic mirror, to generate high-efficient dual-band and ultra-wideband photonic spin-orbit interaction (PSOI) and geometric phase. Two scattering engineered metasurfaces have been designed to reduce the specular reflection, the first one can suppress both the specular reflectances at 1.05-1.08 μm and 5-12 μm below 10%. The second one is designed for an ultra-broadband of 4.6-14 μm, which is actually implemented by cleverly connecting two bands of 4.6-6.1 μm and 6.1-14 μm. Furthermore, the presented structures exhibit low thermal emission at the same time due to the low absorption loss of silicon in infrared spectrum, which can be regarded as an achievement of laser-infrared compatible camouflage. We believe the proposed strategy may open a new route to implement multispectral electromagnetic modulation and multiphysical engineering applications.
Visible Raman and Brillouin lasers from a microresonator/ZBLAN-fiber hybrid system
Shuisen Jiang, Changlei Guo, Kai-Jun Che, Zhengqian Luo, Tuanjie Du, Hongyan Fu, Huiying XU, and Zhiping Cai
Doc ID: 351318 Received 08 Nov 2018; Accepted 13 Mar 2019; Posted 14 Mar 2019 View: PDF
Abstract: Raman and Brillouin lasers based on high Q whispering gallery mode microresonator (WGMR) is achieved usually by employing a tunable single frequency laser (TSFL) as pump source. Here, we experimentally demonstrate visible Raman and Brillouin lasers from a compact microresonator/ZBLAN-fiber hybrid system by incorporating a WGMR with fiber-compatible distributed bragg reflector (DBR)/fiber Bragg grating (FBG) to form F-P fiber cavity and using a piece of Pr:ZBLAN fiber as gain medium. The high Q silica-microsphere not only offers a Rayleigh-scattering induced back-reflection to form the ~635 nm red laser oscillation in the F-P fiber cavity, but also provide a nonlinear gain in the WGMR itself to generate either stimulated Raman scattering (SRS) or stimulated Brillouin scattering (SBS). Up to six-order cascaded Raman lasers at 0.65 μm, 0.67 μm, 0.69 μm, 0.71 μm, 0.73 μm and 0.76 μm are achieved, respectively. Moreover, a Brillouin laser at 635.54 nm is clearly observed. This is, to the best of our knowledge, the first demonstration of visible microresonator-based lasers by combining a Pr:ZBLAN fiber. This novel structure can effectively extend the laser wavelength in WGMR to visible waveband and may find potential applications in underwater-communication, biomedical diagnosis, microwave generation and spectroscopy.
Fiber laser with simultaneous multi-wavelength Er/Yb passively Q-switched and single wavelength Tm gain-switched operations
jared alaniz baylon, Manuel Duran-Sanchez, Ricardo Alvarez Tamayo, Berenice Posada Ramirez, Miguel Bello Jiménez, Baldemar Ibarra-Escamilla, Arturo Alberto. Castillo-Guzman, and Evgeny Kuzin
Doc ID: 358697 Received 25 Jan 2019; Accepted 12 Mar 2019; Posted 14 Mar 2019 View: PDF
Abstract: We report the experimental investigation of an all-fiber multi-wavelength passively Q-switched Er/Yb laser with simultaneous gain-switched pulsed operation by using a thulium-doped fiber as saturable absorber. Laser emission is obtained at three wavelength regions with central peak at around 1546, 1561, and 1862 nm. Multi-wavelength emission with separation of approximately 1 nm is obtained around the wavelength regions of 1546 and 1561 nm. Stable laser pulses are generated in the pump power range from 3.6 to 7.3 W.
Hybrid-typed white LEDs based on Inorganic halide perovskite QDs – a candidate for wide color gamut display backlights
Chih-Hao Lin, Akta Verma, Chieh-Yu Kang, Yung-Min Pai, Tzu-Yu Chen, Jin-Jia Yang, Chin Wei Sher, YA-ZHU Yang, Po-Tsung Lee, Chien-Chung Lin, YU-CHUAN WU, Shailendra Sharma, Tingzhu Wu, Shu-Ru Chung, and Hao-chung Kuo
Doc ID: 356364 Received 28 Dec 2018; Accepted 11 Mar 2019; Posted 14 Mar 2019 View: PDF
Abstract: We demonstrate colloidal halide perovskite quantum dots based white light-emitting diodes (LEDs) via three different geometries including liquid, solid and hybrid types. Problems of fast anion-exchange and aggregation in case of liquid- and solid-typed devices are discussed in detail that push us to move towards fabrication of hybrid-typed device structure. The experiment results illustrate that hybrid-typed device has the highest luminous efficiency (51 lm/W) and wide color gamut (122 % of NTSC and 91 % of Rec. 2020). Therefore, we conclude that hybrid-typed device can provide outstanding color gamut for high color gamut display applications.
Alloyed Au-Ag nanorods with desired plasmonic property and stability in harsh environment
Yuan Ni, Caixia Kan, Longbing He, Xingzhong Zhu, Mingming Jiang, and Daning Shi
Doc ID: 354455 Received 11 Dec 2018; Accepted 10 Mar 2019; Posted 11 Mar 2019 View: PDF
Abstract: Bio-chemical molecular detection in nanoscale, based on alloyed nanorods (NRs) with tunable surface plasmon resonance (SPR) properties and high chemical stability, has attracted particular interest. In this work, alloyed Au-Ag NRs with tunable aspect ratios were achieved by annealing Au nanobipyramids directed-Au@Ag core-shell NRs. The core-shell NRs were encapsulated within mesoporous silica outer-shells to avoid the fusion or aggregation. The structural stability of fully alloyed Au-Ag NRs, including chemical and thermal stability, is remarkably improved compared with that of Au@Ag core-shell NRs. The alloyed NRs would maintain the rod-like structure after incubated into etchant solution, while Au@Ag core-shell NRs would decay into nanobipyramids. Additionally, fully alloyed NRs present stable morphology under annealing at high temperatures up to 600 °C in air. Benefiting from excellent structural and chemical stabilities, surface-enhanced Raman scattering effect based on alloyed NRs is stable in harsh environment. Taking advantages of tunable SPR properties (400–2000 nm) and excellent stability, the obtained nanostructures can also be served as drugs carries. Perfect photo-thermal effect induced by the particular SPR of alloyed NRs can improve the release efficiency of drugs.
Defects and solarization in YAG transparent ceramics
Le Zhang, Jiadong Wu, Petr Stepanov, Micah Haseman, Tianyuan Zhou, David Winarski, Pooneh saadatkia, Sahil Agarwal, Farida Selim, hao Yang, qitu Zhang, Yun Wang, CHINGPING WONG, and Hao Chen
Doc ID: 347005 Received 28 Sep 2018; Accepted 09 Mar 2019; Posted 11 Mar 2019 View: PDF
Abstract: Transparent ceramics are emerging as the future materials for laser, scintillation and illumination. In this paper, an interesting and surprising phenomenon in YAG transparent ceramics is reported. UV light leads to significant changes in the microstructure of open volume defects and nano clusters as well as in the optical properties. Light induced lattice relaxation is suggested to be behind this intriguing behavior. The complex F-type color center with broad absorption bands is caused by the aliovalent sintering additives (Ca2+/Mg2+) and impurity iron ions. Two individual peaks in thermoluminescence illustrate both shallow and deep traps. From positron annihilation lifetime, vacancy-clusters and nanovoids are detected and characterized although these free-volume defects could not be observed by high-resolution TEM. The solarization induced by UV irradiation is associated by a change in the structure and size of defect clusters due to lattice relaxation. Therefore, this work shows how UV irradiation leads not only to a change in the charge state of defects but also to a permanent change in the structural defects and their size which significantly affects the optical properties of YAG ceramics and its performance in laser and other optical applications. These results are crucial for advancing transparent ceramics technology.
0.33 mJ, 104.3 W dissipative soliton resonance based on figure-of-9 double-clad Tm-doped oscillator and all-fiber MOPA system
Zhijian Zheng, Deqin Ouyang, Xikui Ren, Jinzhang Wang, Jihong Pei, and Shuangchen Ruan
Doc ID: 349745 Received 31 Oct 2018; Accepted 08 Mar 2019; Posted 08 Mar 2019 View: PDF
Abstract: We demonstrate an all-fiber figure-of-9 double-clad Tm-doped fiber laser (TDFL) operating in dissipative soliton resonance (DSR) regime for the first time. Stable mode-locked rectangular-shape pulses are obtained by using nonlinear amplifying loop mirror (NALM) technique. A long spool of high nonlinear fiber (HNLF) and SMF-28 fiber are used to enhance the nonlinearity of the NALM loop and to obtain a large all-anomalous regime. Output power and pulse energy are further boosted by using a three-stage master oscillator power amplifier (MOPA) system. At maximum pump power, average output power up to 104.3 W with record pulse energy of 0.33 mJ is achieved at 2 μm DSR-based MOPA system.
Widely Tunable Single-mode Lasers Based on Hybrid Square/Rhombus-Rectangular Microcavity
you-zeng hao, Fu-Li Wang, Min Tang, Hai-Zhong Weng, Yue-De Yang, Jin-Long Xiao, and Yong-Zhen Huang
Doc ID: 354920 Received 10 Dec 2018; Accepted 07 Mar 2019; Posted 08 Mar 2019 View: PDF
Abstract: Hybrid square/rhombus-rectangular lasers (HSRRLs) consisting of a Fabry-Pérot (FP) cavity and a square/rhombus microcavity (SRM) are proposed and demonstrated for realizing single mode lasing with a wide wavelength tuning range. The SRM is a deformed square microcavity with a vertex extended to the FP cavity to control the coupled mode field pattern in the FP cavity. Single mode operation with a side mode suppression ratio (SMSR) over 45.3 dB is realized, and a wide wavelength tuning range of 21 nm with SMSR > 35 dB is further demonstrated by adjusting the injection currents of the SRM and the FP cavity simultaneously. Furthermore, a 3-dB modulation bandwidth of 14.1 GHz and an open eye diagram at 35 Gb/s are demonstrated for the HSRRL.
Terahertz emission from layered GaTe crystal due to surface lattice reorganization and in-plane non-cubic mobility anisotropy
Jiangpeng Dong, Kevin Gradwohl, Yadong Xu, Tao Wang, Binbin Zhang, Bao Xiao, Christian Teichert, and Wanqi Jie
Doc ID: 354787 Received 11 Dec 2018; Accepted 06 Mar 2019; Posted 07 Mar 2019 View: PDF
Abstract: In this work, a model based on the optical rectification effect and the photocurrent surge effect is proposed to describe the THz emission mechanism of layered GaTe crystal. As a centrosymmetric crystal, the optical rectification effect arises from the breaking of the inversion symmetry, due to lattice reorganization of the crystal’s surface layer. In addition, the photocurrent surge originating from the unidirectional charge carrier diffusion - due to the non-cubic mobility anisotropy within the layers - produces THz radiation. This is confirmed by both THz emission spectroscopy and electric property characterization. The current surge perpendicular to the layers also makes an important contribution to the THz radiation, which is consistent with its incident angle dependence. Based on our results, we infer that the contribution of optical rectification changes from 90% under normal incidence to % under 40° incidence angle. The results not only demonstrate the THz radiation properties of layered GaTe bulk crystals, but also promise the potential application of THz emission spectroscopy for characterizing the surface properties of layered materials.
Optofluidics in bio-imaging applications
Sihui Chen, Rui Hao, Yi Zhang, and Hui Yang
Doc ID: 357818 Received 22 Jan 2019; Accepted 05 Mar 2019; Posted 07 Mar 2019 View: PDF
Abstract: Bio-imaging generally indicates imaging techniques that acquire biological information from living forms. Recently, the ability to detect, diagnose and monitor pathological, physiological and molecular dynamics is in great demand. While scaling down the observing angle, achieving precise alignment, fast actuation and miniaturized platform become key elements in the next-generation optical imaging systems. Optofluidics, nominally merging optic and microfluidic technologies, is a relatively new research field and it has begun to draw large attentions in the last decade. Given its abilities to manipulate both optic and fluidic functions/elements in the micro-/nano-meter regime, optofluidics shows great potential in bio-imaging to elevate our cognition in sub-celluar and/or molecular level. In this article, we emphasize the development of optofluidics in bio-imaging, from individual components to commercialized applications in a more modularized, systematic sense. Further, we expound our expectations for the near future of optofluidic imaging discipline.
Continuous Wave Operation of GaAsBi Microdisk Lasers at Room Temperature with Large Wavelength Tuning from 1.27 to 1.41 μm
Xiu Liu, Lijuan Wang, Xuan Fang, TaoJie Zhou, Guohong Xiang, Boyuan Xiang, Xueqing Chen, SuiKong Hark, hao liang, Shumin Wang, and Zhaoyu Zhang
Doc ID: 354686 Received 06 Dec 2018; Accepted 05 Mar 2019; Posted 05 Mar 2019 View: PDF
Abstract: Submicron-meter size GaAsBi disk resonators were fabricated using the GaAsBi/GaAs single quantum well (QW) structure grown by molecular beam epitaxy. The GaAsBi/GaAs QW revealed very broad photoluminescence signals in the wavelength range of 1100-1400 nm at 300 K. The 750 nm diameter and 220 nm thick disk resonators were optically pumped and exhibited lasing characteristics with continuous wave operation at room temperature. To our knowledge, it is the first demonstration of lasing wavelength longer than 1.2 μm with a maximum value of 1.4 μm in GaAsBi/GaAs materials system. The lasing wavelength spans about 130 nm by adjusting the disk diameter, covering almost the entire O band. The ultrasmall GaAsBi disk lasers may have great potentials for highly dense on-chip integration with large tunability in the O band.
Limitations of teleporting a qubit via a two-mode squeezed state for all-optical quantum computing
Seok Hyung Lie and Hyunseok Jeong
Doc ID: 353382 Received 05 Dec 2018; Accepted 02 Mar 2019; Posted 05 Mar 2019 View: PDF
Abstract: Recently, a teleportation scheme using a two-mode squeezed state to teleport a photonic qubit, so called a ``hybrid' approach, has been suggested and experimentally demonstrated as a candidate to overcome limitations of all-optical quantum information processing. We find, however, that there exists the upper bound of the fidelity when teleporting a photonic qubit via a two-mode squeezed channel under a lossy environment.The increase of photon loss decreases this bound, and the teleportation better than this limit is impossible even when the squeezing degree of the teleportation channel becomes infinity.Our result indicates that the hybrid scheme can be valid for fault-tolerant quantum computing only when the photon loss rate can be suppressed under a certain limit.
Plasmonic tip internally excited via azimuthal vector beam for surface enhanced Raman spectroscopy
min liu, Wending Zhang, Fanfan Lu, Tianyang Xue, Xin Li, Lu Zhang, Dong Mao, Ligang Huang, Feng Gao, Ting Mei, and Jianlin Zhao
Doc ID: 358064 Received 17 Jan 2019; Accepted 02 Mar 2019; Posted 05 Mar 2019 View: PDF
Abstract: Plasmonic tip integrated with fiber-based structure light field excitation is a powerful tool for Raman examination. Here, we present a method of Raman spectrum enhancement with an Ag-Nanoparticles (Ag-NPs) coated fiber probe internally excited via an azimuthal vector beam (AVB), which is directly generated in a few-mode fiber by using an acoustically-induced fiber grating. Theoretical analysis shows that gap mode can be effectively generated on the surface of the Ag-NPs coated fiber probe excited via AVB. The experimental result shows that intensity of Raman signal obtained with analyte molecules of malachite green (MG) by exciting the Ag-NPs coated fiber probe via AVB is ~8 times as strong as that of linear polarization beam (LPB) excitation, and the activity of the AVB-excited fiber probe can reach to 10¯¹¹ M, which cannot be achieved by using LPB excitation. Moreover, the time stability and the reliability are also examined, respectively.
Reconfigurable directional coupler in lithium niobate crystal fabricated by three-dimensional femtosecond laser focal field engineering
Qian Zhang, LI MENG, Jian Xu, Zijie Lin, Haofeng Yu, Min Wang, Zhiwei Fang, Ya Cheng, Qihuang Gong, and Yan Li
Doc ID: 355014 Received 11 Dec 2018; Accepted 01 Mar 2019; Posted 05 Mar 2019 View: PDF
Abstract: For crystals, depressed cladding waveguides have advantages such as the preservation of the spectroscopic as well as non-linear properties and the capability to guide both horizontal and vertical polarization modes, but the fabrication is always quite time-consuming. In addition, it’s usually difficult to couple modes propagating in different depressed cladding waveguides through evanescent field overlap so that it is often required to dynamically reconfigure photonic waveguide devices using external fields for classical or quantum applications. Here, we experimentally demonstrate the single-scan femtosecond laser transverse writing of depressed cladding waveguides to form a 2 x 2 directional coupler inside lithium niobate crystal, which is integrated with two deeply embedded microelectrodes on both sides of the interaction region to reconfigure the coupling. By focal field engineering of the femtosecond laser, we specially generate three-dimensional longitudinally oriented ring-shaped focal intensity profile composed of 16 discrete spots to simultaneously write the entire cladding region. The fabricated waveguides exhibit good single guided modes in two orthogonal polarizations at 1550 nm. By applying voltage to the deeply embedded microelectrodes fabricated with the femtosecond laser ablation followed by the selective electroless plating, we successfully facilitate the light coupling from the input-arm to the cross-arm and thus actively tune the splitting ratio. These results open new important perspectives in the efficient fabrication of reconfigurable complex three-dimensional devices in crystals based on depressed cladding waveguides.
MOVPE-grown AlGaN-based tunnel heterojunctions enabling fully transparent UVC LEDs
Christian Kuhn, Luca Sulmoni, Martin Guttmann, Johannes Glaab, Norman Susilo, Tim Wernicke, Markus Weyers, and Michael Kneissl
Doc ID: 356525 Received 07 Jan 2019; Accepted 25 Feb 2019; Posted 26 Feb 2019 View: PDF
Abstract: We report on AlGaN-based tunnel heterojunctions grown by metalorganic vapor phase epitaxy enabling fully transparent UVC LEDs by eliminating the absorbing p-AlGaN and p-GaN layers. Furthermore, the electrical characteristics can be improved by exploiting the higher conductivity of n-AlGaN layers as well as a lower resistance of n-contacts. UVC LEDs with AlGaN:Mg/AlGaN:Si tunnel junctions exhibiting single peak emission at 268 nm have been realized, demonstrating effective carrier injection into the AlGaN MQW active region. The incorporation of a low band gap interlayer enables effective tunneling and a strong voltage reduction. Therefore, the interlayer thickness is systematically varied. Tunnel heterojunction LEDs with 8 nm thick GaN interlayer exhibit cw emission powers > 3 mW near thermal roll-over. External quantum efficiencies of 1.4% at a dc current of 5 mA and operating voltages of 20 V were measured on-wafer. Laterally homogeneous emission is demonstrated by UV-sensitive electroluminescence microscopy images. The complete UVC LED heterostructure was grown in a single epitaxy process including in-situ activation of the magnesium acceptors.
Transparent Conductive Oxide-Gated Silicon Microring with Extreme Resonance Wavelength Tunability
Erwen Li, behzad ashrafi nia, Bokun Zhou, and Alan Wang
Doc ID: 358222 Received 21 Jan 2019; Accepted 22 Feb 2019; Posted 22 Feb 2019 View: PDF
Abstract: Transparent conductive oxides have attracted escalating research interests in integrated photonic devices and metasurfaces due to the extremely large electro-optic modulation of the refractive index by the free carrier-induced plasma dispersion effect. In this paper, we designed and fabricated a silicon microring resonator with indium-tin oxide gate as the electric-tuning electrode. It achieved a quality factor of ~13,000 with ultra-large resonance wavelength tunability of 271pm/V, which is obtained through the reduced width of the ring waveguide and the high dielectric constant HfO2 insulator. We demonstrated a broad resonance wavelength tuning range over 2 nm with ultra-fast response time less than 12 ns and near-zero static power consumption, which outperforms traditional thermal tuning.
Controlling multi-photon excited energy transfer from Tm3+ to Yb3+ ions by phase-shaped femtosecond laser field
Ye Zheng, Lianzhong Deng, Jianping Li, Tianqing Jia, Jianrong Qiu, Zhenrong Sun, and shi zhang
Doc ID: 355499 Received 18 Dec 2018; Accepted 20 Feb 2019; Posted 21 Feb 2019 View: PDF
Abstract: It is very important to have the ability to control the energy transfer in the rare-earth ion doped luminescent materials for various related application areas, such as color display, bio-labeling and new light sources. Here, a phase-shaped femtosecond laser field is first proposed to control the multi-photon excited energy transfer from Tm3+ to Yb3+ ions in a co-doped glass ceramics. The Tm3+ ions are first sensitized by a femtosecond laser-induced multi-photon absorption, and then a highly efficient energy transfer occurs between the highly excited state Tm3+ sensitizers and the ground state Yb3+ activators. The laser power and polarization dependences of the laser-induced luminescence intensities are shown to be served as the proof of the multi-photon excited energy transfer pathway. The multi-photon excited energy transfer efficiency can be efficiently enhanced or completely suppressed by optimizing the femtosecond laser spectral phase with a feedback control strategy based on genetic algorithm. A (1+2) resonance-mediated three-photon excitation model is presented to explain the experimental observations. This study provides a new way to induce and control the energy transfer in the rare-earth ion doped luminescent materials, and should have a positive contribution to the development of related applications.
Non-Hermitian degeneracies of internal-external mode pairs in dielectric microdisks
Julius Kullig, Chang-Hwan Yi, Martina Hentschel, and Jan Wiersig
Doc ID: 357992 Received 22 Jan 2019; Accepted 19 Feb 2019; Posted 19 Feb 2019 View: PDF
Abstract: Open quantum and wave systems can exhibit non-Hermitian degeneracies called exceptional points, where not only the eigenvalues but also the corresponding eigenstates coalesce. Previously, such exceptional points have been investigated in dielectric microcavities in terms of optical modes which are well confined inside the cavity. However, beside these so-called "internal modes" with a relatively high quality factor there exist another kind of modes called "external modes" which have a large decay rate and almost zero intensity inside the cavity. In the present paper we demonstrate the physical significance of the external modes via the occurrence of exceptional points of internal-external mode pairs for transverse electric polarization. Our numerical studies show that these exceptional points can be achieved by either a boundary deformation of the microdisk or by introducing absorption in a circular cavity.
Transparently Curved Metamaterial with Broadband Millimeter Wave Absorption
Cheng Zhang, Jin Yang, Wenkang Cao, Wei Yuan, Junchen Ke, Liuxi Yang, Qiang Cheng, and Tie Jun Cui
Doc ID: 350020 Received 02 Nov 2018; Accepted 14 Feb 2019; Posted 15 Feb 2019 View: PDF
Abstract: We present a conformal metamaterial with simultaneous optical transparency and broadband millimeter-wave absorption for curved surface. By tailoring the reflection response of meta-atoms at oblique angles, it is possible to achieve excellent absorption performance from 26.5 to 40.0 GHz within a wide angular range from 0° to 60° for transverse-electric and transverse-magnetic waves. In the meantime, by employing transparent substrates including the polyvinyl chloride and polyethylene terephthalate, good optical transmittance (80.1%) and flexibility are simultaneously obtained. The reflectivity of curved metallic surface coated by the proposed curved metamaterial is simulated and experimentally measured. Both results demonstrate excellent absorption performance of the metamaterial, which is highly favored for practical applications.
Revealing of the ultrafast third-order nonlinear optical response and enabled photonic application in two-dimensional Tin Sulfide (SnS)
Zhongjian Xie, Feng Zhang, Zhiming Liang, Taojian Fan, zhongjun li, xiantao Jiang, Hong Chen, Jianqing Li, and Han Zhang
Doc ID: 356070 Received 26 Dec 2018; Accepted 11 Feb 2019; Posted 22 Feb 2019 View: PDF
Abstract: Black phosphorus (BP), a typical mono-elemental and two-dimensional (2D) material, has gathered significant attention owing to its distinct optoelectronic properties and promising applications, yet with the main obstacle of long-term stability. Consequently, BP-analogue materials with long-term chemical stability show additional potentials. In this contribution, tin sulfide (SnS), a novel two-elemental and 2D structural BP-analogue monochalcogenide, had been demonstrated to show enhanced stability under ambient conditions. The broadband nonlinear optical properties and carrier dynamics have been systematically investigated via Z-scan and transient absorption approaches. The excellent nonlinear absorption coefficient of 50.5×10-3 cm/GW, one order of magnitude larger than that of BP, endows the promising application of SnS in ultrafast laser generations. Two different decay times of τ1~873 fs and τ2 ~96.9 ps allow the alteration between pure Q-switching and CW mode-locking in an identical laser resonator. Both mode-locked and Q-switched operations have been experimentally demonstrated using SnS saturable absorber (SA) at the telecommunication window. Femtosecond laser pulse with tunable wavelength and high stability are readily to be obtained, suggesting the promising potential of SnS as an efficient optical modulator for ultrafast photonics. This primary investigation may be considered as an important step towards stable and high-performance BP-analogue material-based photonics devices.