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2018, 6(4) Column

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Photonics Research 第6卷 第4期

Author Affiliations
Abstract
1 Research & Innovation, Technicolor R&D France, 975 avenue des Champs Blancs, 35576 Cesson-Sévigné, France
2 CCQCN, Department of Physics, University of Crete, P.O. Box 2208, 71003 Heraklion, Greece
3 College of Optics & Photonics-CREOL, University of Central Florida, Orlando, Florida 32816, USA
4 Institute of Electronic Structure and Laser, Foundation for Research and Technology–Hellas, P.O. Box 1527, 71110 Heraklion, Greece
5 National University of Science and Technology MISiS, Leninsky prosp. 4, Moscow 119049, Russia
The effect of material dispersion on the optical properties of one-dimensional non-Hermitian scattering systems is investigated in detail. In particular, multilayer heterostructures with gain and loss (parity-time symmetric or not) are examined by taking into account the dispersion of each layer. The exceptional points and phase transitions are characterized based on the spectrum of the corresponding scattering matrix. We demonstrate that an on-average lossy heterostructure can amplify an incident plane wave in the frequency range associated with the emission frequency of the layer with gain.
Multilayers Photonic crystals 
Photonics Research
2018, 6(4): 040000A1
Author Affiliations
Abstract
1 Nonlinear Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, ACT 2601, Australia
2 School of Mathematical and Physical Sciences, University of Technology Sydney, Ultimo, NSW 2007, Australia
Integrated nonlinear waveguide structures enable generation of quantum entangled photons. We describe theoretically the effects of spatially inhomogeneous loss on the creation of photon pairs through spontaneous parametric down-conversion in quadratically nonlinear directional couplers, where photons experience effective parity-time (PT) symmetric potential due to the presence of optical loss in one of the waveguides. We show that for losses below the PT-breaking threshold, the quantum photon states can be flexibly tuned similarly to conservative couplers, whereas for stronger losses, the correlations between two waveguide modes are suppressed. We also formulate a quantum-classical correspondence with sum-frequency generation for fast evaluation of device performance. These results can be applied for the design of quantum plasmonic circuits.
Nonlinear optics, parametric processes Nonlinear optics, integrated optics Systems with special symmetry 
Photonics Research
2018, 6(4): 040000A6
Author Affiliations
Abstract
MOE Key Laboratory of Material Physics and Chemistry under Extraordinary Conditions, and Shaanxi Key Laboratory of Optical Information Technology, School of Science, Northwestern Polytechnical University, Xi’an 710129, China
We propose an efficient and robust method to generate tunable vector beams by employing a single phase-type spatial light modulator (SLM). With this method, a linearly polarized Gaussian beam can be converted into a vector beam with arbitrarily controllable polarization state, phase, and amplitude. The energy loss during the conversion is greatly reduced and depends mainly on the reflectivity of the SLM. We experimentally demonstrate that conversion efficiency of about 47% is achieved by using an SLM with reflectivity of 62%. Several typical vector beams, including cylindrical vector beams, vector beams on higher order Poincaré spheres, and arbitrary vector beams attached with phases and with tunable amplitude, are generated and verified experimentally. This method is also expected to create high-power vector beams and play important roles in optical fabrication and light trapping.
Polarization Singular optics Spatial light modulators 
Photonics Research
2018, 6(4): 04000228
Author Affiliations
Abstract
1 Joint Institute for High Temperatures, RAS, Moscow 125412, Russia
2 National Research Nuclear University “MEPhI,” Moscow 115409, Russia
3 M. V. Lomonosov Moscow State University, Moscow 119991, Russia
4 Open and Transdisciplinary Research Initiative, Osaka University, Osaka 565-0871, Japan
5 Graduated School of Engineering, Osaka University, Osaka 565-0871, Japan
6 York Plasma Institute, Department of Physics, University of York, York YO10 5DD, UK
7 Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
8 Department of Physics, SUPA, University of Strathclyde, Glasgow G4 0NG, UK
9 Sandia National Laboratories, Albuquerque, New Mexico 87123, USA
10 Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
X-ray absorption spectroscopy is proposed as a method for studying the heating of solid-density matter excited by secondary X-ray radiation from a relativistic laser-produced plasma. The method was developed and applied to experiments involving thin silicon foils irradiated by 0.5–1.5 ps duration ultrahigh contrast laser pulses at intensities between 0.5×1020 and 2.5×1020 W/cm2. The electron temperature of the material at the rear side of the target is estimated to be in the range of 140–300 eV. The diagnostic approach enables the study of warm dense matter states with low self-emissivity.
Plasma diagnostics Absorption Spectroscopy, x-ray 
Photonics Research
2018, 6(4): 04000234
Mulong Liu 1,2Leiran Wang 1,2,*Qibing Sun 1Siqi Li 1,2[ ... ]Wei Zhao 1,2
Author Affiliations
Abstract
1 State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics (XIOPM), Chinese Academy of Sciences (CAS), Xi’an 710119, China
2 University of Chinese Academy of Sciences, Beijing 100049, China
3 e-mail: wfuzhang@opt.ac.cn
We investigate frequency-comb generation in normal dispersion silicon microresonators from the near-infrared to mid-infrared wavelength range in the presence of multiphoton absorption and free-carrier effects. It is found that parametric oscillation is inhibited in the telecom wavelength range resulting from strong two-photon absorption. On the contrary, beyond the wavelength of 2200 nm, where three- and four-photon absorption are less detrimental, a comb can be generated with moderate pump power, or free-carriers are swept out by a positive-intrinsic-negative structure. In the temporal domain, the generated combs correspond to flat-top pulses, and the pulse duration can be easily controlled by varying the laser detuning. The reported comb generation process shows a high conversion efficiency compared with anomalous dispersion regime, which can guide and promote comb formation in materials with normal dispersion. As the comb spectra cover the mid-infrared wavelength range, they can find applications in comb-based radiofrequency photonic filters and mid-infrared spectroscopy.
Nonlinear optics, four-wave mixing Nonlinear optics, integrated optics Parametric oscillators and amplifiers Microcavities 
Photonics Research
2018, 6(4): 04000238
Author Affiliations
Abstract
1 NANOTAM-Nanotechnology Research Center, Bilkent University, 06800 Ankara, Turkey
2 Department of Electrical and Electronics Engineering, Bilkent University, 06800 Ankara, Turkey
3 UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, 06800 Ankara, Turkey
4 Department of Physics, Bilkent University, 06800 Ankara, Turkey
5 e-mail: amir@ee.bilkent.edu.tr
In this paper, for the first time to our knowledge in the literature, we demonstrate photoluminescence from two-dimensional (2D) vanadium diselenide (VSe2) nanosheets (NSs). The preparation of these nanostructures is carried out with a combinational method based on nanosecond pulsed laser ablation (PLA) and chemical exfoliation. For this aim, VSe2 bulk is first ablated into nanoparticles (NPs) inside a water solution. Afterward, NPs are chemically exfoliated into NSs using lithium intercalation via ultrasonic treatment. Although VSe2 is a semimetal in its bulk form, its nanostructures show photo-responsive behavior, and it turns into a strongly luminescent material when it is separated into NSs. Based on the obtained results, the surface defects induced during the PLA process are the origin of this photoluminescence from NSs. Our findings illustrate that this new material can be a promising semiconductor for photovoltaic and light emitting diode applications.
Semiconductors Optical materials Photoluminescence 
Photonics Research
2018, 6(4): 04000244
Author Affiliations
Abstract
1 School of Information Science and Technology, ShanghaiTech University, Shanghai 201210, China
2 Microelectronic Research Center, Department of Electrical and Computer Engineering, University of Texas, Austin, Texas 78758, USA
3 Omega Optics, Inc., 8500 Shoal Creek Boulevard, Austin, Texas 78757, USA
4 e-mail: chenrt@austin.utexas.edu
Silicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics, high index contrast, small footprint, and low cost, as well as its optical transparency in the near-infrared and parts of mid-infrared (MIR) wavelengths (from 1.1 to 8 μm). While considerations of micro- and nano-fabrication-induced device parameter deviations and a higher-than-desirable propagation loss still serve as a bottleneck in many on-chip data communication applications, applications as sensors do not require similar stringent controls. Photonic devices on chips are increasingly being demonstrated for chemical and biological sensing with performance metrics rivaling benchtop instruments and thus promising the potential of portable, handheld, and wearable monitoring of various chemical and biological analytes. In this paper, we review recent advances in MIR silicon photonics research. We discuss the pros and cons of various platforms, the fabrication procedures for building such platforms, and the benchmarks demonstrated so far, together with their applications. Novel device architectures and improved fabrication techniques have paved a viable way for realizing low-cost, high-density, multi-function integrated devices in the MIR. These advances are expected to benefit several application domains in the years to come, including communication networks, sensing, and nonlinear systems.
Integrated optics devices Waveguides Infrared Photonic integrated circuits 
Photonics Research
2018, 6(4): 04000254
Author Affiliations
Abstract
School of Electrical Engineering and Computer Science, Oregon State University, Corvallis, Oregon 97331, USA
Transparent conductive oxides have emerged as a new type of plasmonic material and demonstrated unique electro-optic (E-O) modulation capabilities for next-generation photonic devices. In this paper, we report an ultra-compact, broadband electro-absorption (EA) modulator using an epsilon-near-zero (ENZ) indium-tin oxide (ITO). The device is fabricated on a standard silicon-on-insulator platform through the integration with a 3 μm long, 300 nm wide gold plasmonic slot waveguide. The active E-O modulation region consists of a metal–HfO2–ITO capacitor that can electrically switch the ITO into ENZ with ultra-high modulation strengths of 2.62 and 1.5 dB/μm in simulation and experiment, respectively. The EA modulator also demonstrated a uniform E-O modulation with 70 nm optical bandwidth from 1530 to 1600 nm wavelength.
Integrated optics devices Modulators Surface plasmons Waveguide modulators 
Photonics Research
2018, 6(4): 04000277
Author Affiliations
Abstract
1 Hubei Key Laboratory of Intelligent Wireless Communications, College of Electronics and Information Engineering, South-Central University for Nationalities, Wuhan 430074, China
2 King Abdullah University of Science and Technology (KAUST), Advanced Semiconductor Laboratory, Thuwal 23955-6900, Saudi Arabia
Connected-annular-rods photonic crystals (CARPCs) in both triangular and square lattices are proposed to enhance the two-dimensional complete photonic bandgap (CPBG) for chalcogenide material systems with moderate refractive index contrast. For the typical chalcogenide-glass–air system with an index contrast of 2.8:1, the optimized square lattice CARPC exhibits a significantly larger normalized CPBG of about 13.50%, though the use of triangular lattice CARPC is unable to enhance the CPBG. It is almost twice as large as our previously reported result [IEEE J. Sel. Top. Quantum Electron.22, 4900108 (2016)IJSQEN1077-260X10.1109/JSTQE.2015.2422997]. Moreover, the CPBG of the square-lattice CARPC could remain until an index contrast as low as 2.24:1. The result not only favors wideband CPBG applications for index contrast systems near 2.8:1, but also makes various optical applications that are dependent on CPBG possible for more widely refractive index contrast systems.
Photonic crystals Photonic bandgap materials Glass and other amorphous materials Bragg reflectors Polarization 
Photonics Research
2018, 6(4): 04000282
Author Affiliations
Abstract
1 Low Energy Electronic Systems (LEES), Singapore-MIT Alliance for Research and Technology (SMART), 1 CREATE Way, #10-01 CREATE Tower, Singapore 138602, Singapore
2 School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
3 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
4 e-mail: tancs@ntu.edu.sg
High-performance GaInP/AlGaInP multi-quantum well light-emitting diodes (LEDs) grown on a low threading dislocation density (TDD) germanium-on-insulator (GOI) substrate have been demonstrated. The low TDD of the GOI substrate is realized through Ge epitaxial growth, wafer bonding, and layer transfer processes on 200 mm wafers. With O2 annealing, the TDD of the GOI substrate can be reduced to 1.2×106 cm 2. LEDs fabricated on this GOI substrate exhibit record-high optical output power of 1.3 mW at a 670 nm peak wavelength under 280 mA current injection. This output power level is at least 2 times higher compared to other reports of similar devices on a silicon (Si) substrate without degrading the electrical performance. These results demonstrate great promise for the monolithic integration of visible-band optical sources with Si-based electronic circuitry and realization of high-density RGB (red, green, and blue) micro-LED arrays with control circuitry.
Light-emitting diodes Semiconductors Semiconductor materials 
Photonics Research
2018, 6(4): 04000290
Author Affiliations
Abstract
1 Shanghai Key Laboratory of Modern Optical Systems, College of Optics and Electronic Information Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
2 Institute of Modern Optics, Key Laboratory of Optical Information Science and Technology, Ministry of Education, Nankai University, Tianjin 300071, China
3 Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, China
4 e-mail: py@usst.edu.cn
5 e-mail: ymzhu@usst.edu.cn
In this work, it has been demonstrated that in order to fully understand the terahertz (THz) pulse generation process during femtosecond laser filamentation, the interaction between THz wave and air plasma has to be taken into account. This interaction is mainly associated with the spatial confinement of the THz pulse by the plasma column, which could be described by the one-dimensional negative dielectric (1DND) waveguide model. By combining the 1DND model with the conventional four-wave mixing (4WM) and photocurrent (PC) models, the variation of THz spectral amplitude and width obtained in experiments could be better understood. Finally, a three-step procedure, with 1DND bridging 4WM and PC processes, has been established for the first time to describe the underlying mechanism of THz radiation from plasma sources.
Ultrafast nonlinear optics Femtosecond phenomena Plasmas Propagation Spectroscopy, terahertz 
Photonics Research
2018, 6(4): 04000296
Author Affiliations
Abstract
1 State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
2 Research Institute of Science and Technology, Shandong University, Jinan 250100, China
3 e-mail: xphao@sdu.edu.cn
For the first time to our knowledge, graphitic carbon nitride (g-C3N4) nanosheets are found to be an excellent saturable absorber material in the visible waveband. g-C3N4 exhibits much stronger saturable absorption in this region than in the near-infrared region, unlike other two-dimensional materials such as graphene and black phosphorus. By the Z-scan method, the nonlinear absorption coefficient β of the material is first measured at three visible wavelengths, and for g-C3N4 it is 2.05, 0.34, and 0.11 cm·GW 1 at 355, 532, and 650 nm, respectively. These are much larger than 0.06 cm·GW 1 at 1064 nm.
Nonlinear optical materials Nanomaterials Nonlinear optics, materials 
Photonics Research
2018, 6(4): 04000307
Author Affiliations
Abstract
1 School of Information Science and Engineering, Shandong University, Jinan 250100, China
2 Department of Photonics, Taiwan Sun Yat-sen University, 70 Lienhei Road, Kaohsiung 80424, China
3 State Key Laboratory of Crystal Materials, Institute of Crystal Materials, Shandong University, Jinan 250100, China
4 Research Center for Applied Sciences, Academia Sinica, 128 Sec. 2, Academic Road, Taipei 11529, China
5 e-mail: shengzhi_zhao@sdu.edu.cn
6 e-mail: chuckcklee@yahoo.com
In this paper, the fabrication process and characterization of Bi2Te3 topological insulators (TIs) synthesized by the spin-coating-coreduction approach (SCCA) is reported. With this approach, high-uniformity nano-crystalline TI saturable absorbers (TISAs) with large-area uniformity and controllable thickness are prepared. By employing these prepared TIs with different thicknesses as SAs in 2-μm solid-state Q-switched lasers, thickness-dependent output powers and pulse durations of the laser pulses are obtained, and the result also exhibits stability and reliability. The shortest pulse duration is as short as 233 ns, and the corresponding clock amplitude jitter is around 2.1%, which is the shortest pulse duration in TISA-based Q-switched 2-μm lasers to the best of our knowledge. Moreover, in comparison with the TISA synthesized by the ultrasound-assisted liquid phase exfoliation (UALPE) method, the experimental results show that lasers with SCCA synthesized TISAs have higher output powers, shorter pulse durations, and higher pulse peak powers. Our work suggests that the SCCA synthesized TISAs could be used as potential SAs in pulsed lasers.
Lasers, Q-switched Optical properties 
Photonics Research
2018, 6(4): 04000314
Author Affiliations
Abstract
1 State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876, China
2 State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
3 Laboratory of Nano Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
4 Engineering Research Center for Semiconductor Integrated Technology, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
5 Department of Electronic & Electrical Engineering, University College London, London WC1E 7JE, UK
We report on the first electrically pumped continuous-wave (CW) InAs/GaAs quantum dot (QD) laser grown on Si with a GaInP upper cladding layer. A QD laser structure with a Ga0.51In0.49P upper cladding layer and an Al0.53Ga0.47As lower cladding layer was directly grown on Si by metal–organic chemical vapor deposition. It demonstrates the postgrowth annealing effect on the QDs was relieved enough with the GaInP upper cladding layer grown at a low temperature of 550°C. Broad-stripe edge-emitting lasers with 2-mm cavity length and 15-μm stripe width were fabricated and characterized. Under CW operation, room-temperature lasing at 1.3 μm has been achieved with a threshold density of 737 A/cm2 and a single-facet output power of 21.8 mW.
Quantum-well, -wire and -dot devices Semiconductor lasers Integrated optics materials 
Photonics Research
2018, 6(4): 04000321
Author Affiliations
Abstract
1 State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology, Guangzhou 510640, China
2 College of Optoelectronic Technology, Chengdu University of Information Technology, Chengdu 610225, China
3 Guangdong Engineering Technology Research and Development Center of High-Performance Fiber Laser Techniques and Equipments, Zhuhai 519031, China
4 Guangdong Engineering Technology Research and Development Center of Special Optical Fiber Materials and Devices, Guangzhou 510640, China
5 Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques, South China University of Technology, Guangzhou 510640, China
A noise-sidebands-free and ultra-low relative intensity noise (RIN) 1.5 μm single-frequency fiber laser is demonstrated for the first time to our best knowledge. Utilizing a self-injection locking framework and a booster optical amplifier, the noise sidebands with relative amplitudes as high as 20 dB are completely suppressed. The RIN is remarkably reduced by more than 64 dB at the relaxation oscillation peak to retain below 150 dB/Hz in a frequency range from 75 kHz to 50 MHz, while the quantum noise limit is 152.9 dB/Hz. Furthermore, a laser linewidth narrower than 600 Hz, a polarization-extinction ratio of more than 23 dB, and an optical signal-to-noise ratio of more than 73 dB are acquired simultaneously. This noise-sidebands-free and ultra-low-RIN single-frequency fiber laser is highly competitive in advanced coherent light detection fields including coherent Doppler wind lidar, high-speed coherent optical communication, and precise absolute distance coherent measurement.
Lasers, fiber Lasers, single-mode Fluctuations, relaxations, and noise 
Photonics Research
2018, 6(4): 04000326
Author Affiliations
Abstract
1 School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
2 School of Science, Qingdao University of Technology, Qingdao 266520, China
3 Faculty of Electronic Information Engineering, Huaiyin Institute of Technology, Huaian 223003, China
A microcavity laser based on evanescent-wave-coupled gain is formed using a silica fiber with a diameter of 125 μm in a rhodamine 6G ethanol solution. When the fiber is sticking to the cuvette wall by capillary force, using the excitation of a 532 nm nanosecond pulsed laser, single-mode laser emission is observed. While increasing the distance between the fiber and the cuvette wall, the typical multi-peak whispering-gallery-mode (WGM) laser emission can also be demonstrated. On the other hand, while increasing the refractive index of the solution by mixing ethanol and ethylene glycol with different ratios as a solvent, the single-mode emission would evolve to multi-peak WGM laser emission controllably.
Microcavities Lasers, single-mode Integrated optics devices 
Photonics Research
2018, 6(4): 04000332
Author Affiliations
Abstract
1 College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China
2 Institute of Optoelectronic Technology, China Jiliang University, Hangzhou 310018, China
3 e-mail: sxucjlu@163.com
Er/Ho co-doped oxyfluoride germanosilicate glass and glass ceramics are prepared and compared. The results indicate that the glass consists of SiO4 and GeO4 structural units, while the network of the glass ceramics consists of SiO4, GeO4, and GeO6 units together with NaYF4 nanocrystals. The presence of multiple local structures in glass ceramics creates a range of dipole environments, which is beneficial to the broadening of 2.7 μm emission. Two other reasons are attributed to the broadening of 2.7 μm emission in glass ceramics: the energy-level splitting of Er3+ and the enhancement of the Ho3+:I65I75 transition in NaYF4 nanocrystals.
Rare-earth-doped materials Laser materials Glass and other amorphous materials Spectroscopy, infrared 
Photonics Research
2018, 6(4): 04000339
Li Ge 1,2,*
Author Affiliations
Abstract
1 Department of Engineering Science and Physics, College of Staten Island, CUNY, Staten Island, New York 10314, USA
2 The Graduate Center, CUNY, New York, New York 10016, USA (li.ge@csi.cuny.edu)
In this work, we first discuss systematically three general approaches to construct a non-Hermitian flat band, defined by its dispersionless real part. These approaches resort to, respectively, spontaneous restoration of non-Hermitian particle-hole symmetry, a persisting flat band from the underlying Hermitian system, and a compact Wannier function that is an eigenstate of the entire system. For the last approach in particular, we show the simplest lattice structure where it can be applied, and we further identify a special case of such a flat band where every point in the Brillouin zone is an exceptional point of order 3. A localized excitation in this “EP3 flat band” can display either a conserved power, quadratic power increase, or even quartic power increase, depending on whether the localized eigenstate or one of the two generalized eigenvectors is initially excited. Nevertheless, the asymptotic wave function in the long time limit is always given by the eigenstate, in this case, the compact Wannier function or its superposition in two or more unit cells.
Guided waves Waveguides Systems with special symmetry Photonic bandgap materials 
Photonics Research
2018, 6(4): 04000A10
Author Affiliations
Abstract
1 Novosibirsk State University, 2 Pirogova Street, Novosibirsk 630090, Russia
2 Nonlinear Physics Centre, Research School of Physics and Engineering, Australian National University, Canberra, ACT 2601, Australia
We propose a parity-time (PT) symmetric fiber laser composed of two coupled ring cavities with gains and losses, which operates both in PT-symmetric and symmetry-broken regimes depending on the static phase shifts. We perform analytical and numerical analysis by the transfer matrix method taking into account gain saturation and predict laser bistability in the PT-symmetric regime in contrast to a symmetry-broken single-mode operation. In the PT-broken regime, the generation power counterintuitively increases with an increase of the cavity losses.
Lasers, fiber Bistability Lasers, ring 
Photonics Research
2018, 6(4): 04000A18