Contents 1 Issue (s), 14 Article (s)

Vol. 10, Iss.10—Oct.1, 2022 • pp: 2267-NGSP3 Spec. pp: A135-A153

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Research ArticlesVol. 10, Iss.10-Oct..1,2022
Holography, Gratings, and Diffraction
Particle manipulation behind a turbid medium based on the intensity transmission matrix
Kaige Liu, Hengkang Zhang, Shanshan Du, Zeqi Liu, Bin Zhang, Xing Fu, and Qiang Liu
Although optical tweezers can manipulate tiny particles, the distortion caused by the scattering medium restricts their application. Wavefront-shaping techniques such as the transmission matrix (TM) method are powerful tools to achieve light focusing behind the scattering medium. In this paper, we propose a method to focus light through a scattering medium in a large area based on the intensity transmission matrix (ITM). Only relying on the intensity distribution, we can calculate the ITM with the number of measurements equal to that of the control segments. Free of the diffraction limit, our method guarantees high energy usage of the light field. Based on this method, we have implemented particle manipulation with a high degree of freedom on single and multiple particles. In addition, the manipulation range is enlarged more than 20 times (compared to the memory effect) to 200 μm.
Photonics Research
  • Publication Date: Sep. 14, 2022
  • Vol. 10, Issue 10, 2293 (2022)
Image Processing and Image Analysis
Speckle spatial correlations aiding optical transmission matrix retrieval: the smoothed Gerchberg–Saxton single-iteration algorithm
Daniele Ancora, Lorenzo Dominici, Antonio Gianfrate, Paolo Cazzato, Milena De Giorgi, Dario Ballarini, Daniele Sanvitto, and Luca Leuzzi
The estimation of the transmission matrix of a disordered medium is a challenging problem in disordered photonics. Usually, its reconstruction relies on a complex inversion that aims at connecting a fully controlled input to the deterministic interference of the light field scrambled by the device. At the moment, iterative phase retrieval protocols provide the fastest reconstructing frameworks, converging in a few tens of iterations. Exploiting the knowledge of speckle correlations, we construct a new phase retrieval algorithm that reduces the computational cost to a single iteration. Besides being faster, our method is practical because it accepts fewer measurements than state-of-the-art protocols. Thanks to reducing computation time by one order of magnitude, our result can be a step forward toward real-time optical imaging that exploits disordered devices.
Photonics Research
  • Publication Date: Sep. 27, 2022
  • Vol. 10, Issue 10, 2349 (2022)
Integrated Optics
Ultra-high-linearity integrated lithium niobate electro-optic modulatorsEditors' Pick
Hanke Feng, Ke Zhang, Wenzhao Sun, Yangming Ren, Yiwen Zhang, Wenfu Zhang, and Cheng Wang
Integrated lithium niobate (LN) photonics is a promising platform for future chip-scale microwave photonics systems owing to its unique electro-optic properties, low optical loss, and excellent scalability. A key enabler for such systems is a highly linear electro-optic modulator that could faithfully convert analog electrical signals into optical signals. In this work, we demonstrate a monolithic integrated LN modulator with an ultra-high spurious-free dynamic range (SFDR) of 120.04 dB·Hz4/5 at 1 GHz, using a ring-assisted Mach–Zehnder interferometer configuration. The excellent synergy between the intrinsically linear electro-optic response of LN and an optimized linearization strategy allows us to fully suppress the cubic terms of third-order intermodulation distortions (IMD3) without active feedback controls, leading to 20 dB improvement over previous results in the thin-film LN platform. Our ultra-high-linearity LN modulators could become a core building block for future large-scale functional microwave photonic integrated circuits by further integration with other high-performance components like low-loss delay lines, tunable filters, and phase shifters available on the LN platform.
Photonics Research
  • Publication Date: Sep. 27, 2022
  • Vol. 10, Issue 10, 2366 (2022)
Integrated Optics
Phase regimes of parity-time-symmetric coupled-ring systems at exceptional points
Zhuang Ma, Xiaoyan Zhou, and Lin Zhang
The optical coupled resonant system consisting of an integrated resonator with gain and a resonator with loss provides an excellent platform to create exceptional points (EPs) in non-Hermitian systems. Most previous studies have focused on the striking intensity feature of EPs, but its phase response is seldom investigated. In this work, we present a thorough study on the phase response of an EP system. Intriguingly, the phase response exhibits distinct behavior depending on the ordering of the ring resonators: when the input light in a bus waveguide is coupled directly or indirectly to the ring with a gain, the phase response is featured by nonmonotonic transition and 2π monotonic transition, respectively. We also prove that the newly identified phase features are theoretically guaranteed. These phase responses produce unique group delays that have never been found in other coupled resonant systems. The results deepen our understanding on EPs in non-Hermitian systems and are potentially useful for practical applications exploiting phase features.
Photonics Research
  • Publication Date: Sep. 28, 2022
  • Vol. 10, Issue 10, 2374 (2022)
Lasers and Laser Optics
High-power wavelength-tunable and power-ratio-controllable dual-wavelength operation at 1319 nm and 1338 nm in a Q-switched Nd:YAG laser
Qi Bian, Yong Bo, Jun-Wei Zuo, Lei Yuan, Hong-Wei Gao, and Qin-Jun Peng
We report the first demonstration on three types of 1.3 μm spectral region in a Q-switched Nd:YAG laser. In order to dissipate the heat deposition effectively to obtain good beam quality, the Nd:YAG rod crystal with 1° cut-angle on end faces is side-pumped by the quasi-continuous-wave pulsed laser diode. A Suprasil etalon is well designed as the intracavity mode-selector to obtain wavelength-tunable single line or power-ratio-controllable dual line operation at 1319 nm and 1338 nm. With the pump pulse width of 200 μs and pump power of 410 W, the acousto-optic Q-switched laser delivered a pulse width of 117 ns at 400 Hz repetition rate, and the M2 factor was measured to be about 1.87. 1319 nm together with 1338 nm single-wavelength laser achieved an average output power of 47.6 W and 39.9 W with a linewidth of 0.48 nm and 0.32 nm, and a tunable range of 111.2 pm and 108.6 pm, respectively. Among dual-wavelength oscillation, both lines can be tuned at almost equal intensity level with 45.7 W total output power, which is input into an LBO crystal to generate red light of 11.4 W for 659 nm, 6.7 W for 664 nm, and 7.5 W for 669 nm. The 1.3 μm wavelength-selectable operation realized by using the same laser configuration may enhance the application in the fields of tunable lasers and THz frequency generation.
Photonics Research
  • Publication Date: Sep. 14, 2022
  • Vol. 10, Issue 10, 2287 (2022)
Nonlinear Optics
Hybrid plasmonic–dielectric metal-nanowire coupler for high-efficiency broadband nonlinear frequency conversion
Kui-Ying Nie, Song Luo, Fang-Fang Ren, Xuanhu Chen, Shulin Gu, Zhanghai Chen, Rong Zhang, and Jiandong Ye
Pursuing nanometer-scale nonlinear converters based on second harmonic generation (SHG) is a stimulating strategy for bio-sensing, on-chip optical circuits, and quantum information processing, but the light-conversion efficiency is still poor in such ultra-small dimensional nanostructures. Herein, we demonstrate a highly enhanced broadband frequency converter through a hybrid plasmonic–dielectric coupler, a ZnTe/ZnO single core–shell nanowire (NW) integrated with silver (Ag) nanoparticles (NPs). The NW dimension has been optimized to allow the engineering of dielectric resonances at both fundamental wave and second harmonic frequencies. Meanwhile, the localized surface plasmon resonances are excited in the regime between the Ag NPs and ZnTe/ZnO dielectric NW, as evidenced by plasmon-enhanced Raman scattering and resonant absorption. These two contributors remarkably enhance local fields and consequently support the strong broadband SHG outputs in this hybrid nanostructure by releasing stringent phase-matching conditions. The proposed nanoscale nonlinear optical converter enables the manipulation of nonlinear light–matter interactions toward the development of on-chip nanophotonic systems.
Photonics Research
  • Publication Date: Sep. 26, 2022
  • Vol. 10, Issue 10, 2337 (2022)
Optical Devices
Compact nano-void spectrometer based on a stable engineered scattering system
Qi Sun, Przemyslaw Falak, Tom Vettenburg, Timothy Lee, David B. Phillips, Gilberto Brambilla, and Martynas Beresna
Random scattering of light in disordered media can be used for highly sensitive speckle-based wavemeters and spectrometers. However, the multiple scattering events that fold long optical paths within a compact space also make such devices exceedingly sensitive to vibrations and small disturbances to the disordered media. Here, we show how scattering can be engineered so that it can be used for a compact computational spectrometer that is largely insensitive to environmental factors. We designed and fabricated a three-dimensional pseudo-random nano-void pattern with 62% scattering efficiency. The controlled amount of multiple scattering ensured a sufficiently long optical path for the target resolution of 100 pm, with optimal long-term stability. The 200-μm-thick scattering silica substrate was integrated in a compact assembly with a low-cost camera sensor. The target resolution was achieved for full spectrum measurements while single wavelengths could be determined with 50 pm resolution. Such tailored scattering systems can improve the trade-off among cost, size, stability, and spectral resolution in computational spectrometers.
Photonics Research
  • Publication Date: Sep. 26, 2022
  • Vol. 10, Issue 10, 2328 (2022)
Optical Devices
High-precision whispering gallery microsensors with ergodic spectra empowered by machine learning
Bing Duan, Hanying Zou, Jin-Hui Chen, Chun Hui Ma, Xingyun Zhao, Xiaolong Zheng, Chuan Wang, Liang Liu, and Daquan Yang
Whispering gallery mode (WGM) microcavities provide increasing opportunities for precision measurement due to their ultrahigh sensitivity, compact size, and fast response. However, the conventional WGM sensors rely on monitoring the changes of a single mode, and the abundant sensing information in WGM transmission spectra has not been fully utilized. Here, empowered by machine learning (ML), we propose and demonstrate an ergodic spectra sensing method in an optofluidic microcavity for high-precision pressure measurement. The developed ML method realizes the analysis of the full features of optical spectra. The prediction accuracy of 99.97% is obtained with the average error as low as 0.32 kPa in the pressure range of 100 kPa via the training and testing stages. We further achieve the real-time readout of arbitrary unknown pressure within the range of measurement, and a prediction accuracy of 99.51% is obtained. Moreover, we demonstrate that the ergodic spectra sensing accuracy is 11.5% higher than that of simply extracting resonating modes’ wavelength. With the high sensitivity and prediction accuracy, this work opens up a new avenue for integrated intelligent optical sensing.
Photonics Research
  • Publication Date: Sep. 26, 2022
  • Vol. 10, Issue 10, 2343 (2022)
Optical Devices
Taming quantum dots’ nucleation and growth enables stable and efficient blue-light-emitting devices
Zhiwei Ma, Junxia Hu, Liping Tang, and Bingbing Lyu
Controlling quantum dots’ emission, nanostructure, and energy level alignment to achieve stable and efficient blue emission is of great significance for electroluminescence devices but remains a challenge. Here, a series of blue ZnCdSeS/ZnS quantum dots was optimized in preparation by taming their nucleation and growth kinetics. Controlling anion precursor reactive properties to modulate quantum dots’ nucleation and growth tailors their alloy core and continuous gradient energy band nanostructure. These results not only elevate the thermal stability of blue quantum dots but also further enhance the injection/transportation of carriers and improve the radiative recombination efficiency in the device. The blue ZnCdSeS/ZnS quantum dots applied in light-emitting devices show superior performance, including maximum current efficiency and external quantum efficiency of, respectively, 8.2 cd/A and 15.8% for blue, 2.6 cd/A and 10.0% for blue-violet, and 10.9 cd/A and 13.4% for sky-blue devices. The blue and sky-blue devices exhibit lifetimes of more than 10,000 h. The proposed methodology for tailoring quantum dots is expected to pave new guidelines for further facilitating visible optoelectronic device exploration.
Photonics Research
  • Publication Date: Sep. 27, 2022
  • Vol. 10, Issue 10, 2359 (2022)
Optoelectronics
High-frequency enhanced response based on Sb2Te3 topological insulators
Shi Zhang, Chaofan Shi, Weiwei Tang, Libo Zhang, Li Han, Chengsen Yang, Zhengyang Zhang, Jian Wang, Miao Cai, Guanhai Li, Changlong Liu, Lin Wang, Xiaoshuang Chen, and Wei Lu
Topological insulators represent a new quantum phase of matter with spin-polarized surface states that are protected from backscattering, exhibiting electronic responses to light, such as topological quantum phase transitions. However, the effects of high-frequency driving topological intrinsic systems have remained largely unexplored challenges experimentally for high-sensitivity terahertz detection. In this study, by integrating Sb2Te3 topological insulators with subwavelength metal antennas through micro-nano processing, a high-frequency terahertz detector with high sensitivity is proposed. The enhanced response originates from the asymmetric scattering of the surface electrons in the Sb2Te3 flakes induced by the terahertz wave. The device displays room-temperature photodetection with a responsivity of 192 mA/W and equivalent noise power of less than 0.35 nW/Hz1/2 in the frequency range from 0.02 to 0.3 THz. These results pave the way for the exploitation of topological insulators for high-frequency operation in real-time imaging within long-wavelength optoelectronics.
Photonics Research
  • Publication Date: Sep. 14, 2022
  • Vol. 10, Issue 10, 2302 (2022)
Optoelectronics
Systematic investigation of millimeter-wave optic modulation performance in thin-film lithium niobate
Yiwen Zhang, Linbo Shao, Jingwei Yang, Zhaoxi Chen, Ke Zhang, Kam-Man Shum, Di Zhu, Chi Hou Chan, Marko Lončar, and Cheng Wang
Millimeter-wave (mmWave) band (30–300 GHz) is an emerging spectrum range for wireless communication, short-range radar, and sensor applications. mmWave-optic modulators that could efficiently convert mmWave signals into the optical domain are crucial components for long-haul transmission of mmWave signals through optical networks. At these ultrahigh frequencies, however, the modulation performances are highly sensitive to the transmission line loss as well as the velocity- and impedance-matching conditions, while precise measurements and modeling of these parameters are often non-trivial. Here we present a systematic investigation of the mmWave-optic modulation performances of thin-film lithium niobate modulators through theoretical modeling, electrical verifications, and electro-optic measurements at frequencies up to 325 GHz. Based on our experimentally verified model, we demonstrate thin-film lithium niobate mmWave-optic modulators with a measured 3-dB electro-optic bandwidth of 170 GHz and a 6-dB bandwidth of 295 GHz. The device also shows a low RF half-wave voltage of 7.3 V measured at an ultrahigh modulation frequency of 250 GHz. This work provides a comprehensive guideline for the design and characterization of mmWave-optic modulators and paves the way toward future integrated mmWave photonic systems for beyond-5G communication and radar applications.
Photonics Research
  • Publication Date: Sep. 28, 2022
  • Vol. 10, Issue 10, 2380 (2022)
Quantum Optics
Hong–Ou–Mandel interference linking independent room-temperature quantum memoriesEditors' Pick
Chao-Ni Zhang, Hang Li, Jian-Peng Dou, Feng Lu, Hong-Zhe Yang, Xiao-Ling Pang, and Xian-Min Jin
To realize a large-scale quantum network, both quantum memory and the interference of retrieved indistinguishable photons are essentially required to perform multi-photon synchronization and quantum-interference-mediated entanglement swapping. Significant progress has been achieved in low-temperature and well-isolated systems. However, linking independent quantum memories at room temperature remain challenging. Here, we present an experimental demonstration of Hong–Ou–Mandel interference between single photons from two independent room-temperature quantum memories. We manage to simultaneously operate two such quantum memories and individually obtain a memory-built-in quantum correlation of Stokes and anti-Stokes photons by a far-off-resonance Duan–Lukin–Cirac–Zoller protocol. We also successfully enhance the Hong–Ou–Mandel interference rate up to about 15 times by increasing each photon rate, which is achieved by coordinating two quantum memories with a repeat-until-success fashion. We observe the visibility of quantum interference up to 75.0% without reduction of any background noise, well exceeding the classical limit of 50%. Our results, together with its straightforward, broadband, and room-temperature features, open up a promising way towards realizing large-scale quantum networks at ambient conditions.
Photonics Research
  • Publication Date: Sep. 29, 2022
  • Vol. 10, Issue 10, 2388 (2022)
Surface Optics and Plasmonics
Flexible manipulation of plasmon dephasing time via the adjustable Fano asymmetric dimer
Yang Xu, Yulu Qin, Peng Lang, Boyu Ji, Xiaowei Song, and Jingquan Lin
It is highly desirable to flexibly and actively manipulate the dephasing time of a plasmon in many potential applications; however, this remains a challenge. In this work, by using femtosecond time-resolved photoemission electron microscopy, we experimentally demonstrated that the Fano resonance mode in the asymmetric nanorod dimer can greatly extend the dephasing time of a femtosecond plasmon, whereas the non-Fano resonance results in a smaller dephasing time due to the large radiative damping, and flexible manipulation of the dephasing time can be realized by adjusting one of the nanorods in the Fano asymmetric dimer. Interestingly, it was found that plasmon resonance wavelengths both appeared red-shifted as the length of the upper or lower nanorods increased individually, but the dephasing time varied. Furthermore, it also indicated that the dephasing time can be prolonged with a smaller ascending rate by increasing the length of both the nanorods simultaneously while keeping the dimer asymmetry. Meanwhile, the roles of radiative and nonradiative damping in dephasing time are unveiled in the process of nanorod length variation. These results are well supported by numerical simulations and calculations.
Photonics Research
  • Publication Date: Sep. 14, 2022
  • Vol. 10, Issue 10, 2267 (2022)
Surface Optics and Plasmonics
High-sensitivity modulation of electromagnetically induced transparency analog in a THz asymmetric metasurface integrating perovskite and graphene
Tongling Wang, Tengteng Li, Haiyun Yao, Yuying Lu, Xin Yan, Maoyong Cao, Lanju Liang, Maosheng Yang, and Jianquan Yao
Active control of the electromagnetically induced transparency (EIT) analog is desirable in photonics development. Here, we theoretically and experimentally proposed a novel terahertz (THz) asymmetric metasurface structure that can possess high-sensitivity modulation under extremely low power density by integrating perovskite or graphene. Using the novel metasurface structure with the perovskite coating, the maximum amplitude modulation depth (AMD) of this perovskite-based device reached 490.53% at a low power density of 12.8037 mW/cm2. In addition, after the novel THz metasurface structure was combined with graphene, this graphene-based device also achieved high AMD with the maximum AMD being 180.56% at 16.312 mW/cm2, and its transmission amplitude could be electrically driven at a low bias voltage. The physical origin of this modulation was explained using a two-oscillator EIT model. This work provides a promising platform for developing high-sensitivity THz sensors, light modulators, and switches.
Photonics Research
  • Publication Date: Sep. 26, 2022
  • Vol. 10, Issue 10, 2317 (2022)