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

Vol. 11, Iss.6—Jun.1, 2023 • pp: 1007-916 Spec. pp:

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Research ArticlesVol. 11, Iss.6-Jun..1,2023
Fiber Optics and Optical Communications
Surpassing the classical limit of the microwave photonic frequency fading effect by quantum microwave photonics
Yaqing Jin, Ye Yang, Huibo Hong, Xiao Xiang, Run'ai Quan, Tao Liu, Ninghua Zhu, Ming Li, Shougang Zhang, and Ruifang Dong
With energy–time entangled biphoton sources as the optical carrier and time-correlated single-photon detection for high-speed radio frequency (RF) signal recovery, the method of quantum microwave photonics (QMWP) has presented the unprecedented potential of nonlocal RF signal encoding and efficient RF signal distilling from the dispersion interference associated with ultrashort pulse carriers. In this paper, its capability in microwave signal processing and prospective superiority are further demonstrated. Both QMWP RF phase shifting and transversal filtering functionality, which are the fundamental building blocks of microwave signal processing, are realized. Besides good immunity to the dispersion-induced frequency fading effect associated with the broadband carrier in classical MWP, a native two-dimensional parallel microwave signal processor is provided. These results well demonstrate the superiority of QMWP over classical MWP and open the door to new application fields of MWP involving encrypted processing.
Photonics Research
  • Publication Date: May. 30, 2023
  • Vol. 11, Issue 6, 1094 (2023)
Holography, Gratings, and Diffraction
Six-channel programmable coding metasurface simultaneously for orthogonal circular and linear polarizations
Tonghao Liu, Yueyu Meng, Jiafu Wang, Hua Ma, Ruichao Zhu, Chao Liu, Weihan Li, Zuntian Chu, Sai Sui, Tianshuo Qiu, Wenxuan Tang, and Shaobo Qu
Metasurfaces have intrigued long-standing research interests and developed multitudinous compelling applications owing to their unprecedented capability for manipulating electromagnetic waves, and the emerging programmable coding metasurfaces (PCMs) provide a real-time reconfigurable platform to dynamically implement customized functions. Nevertheless, most existing PCMs can only act on the single polarization state or perform in the limited polarization channel, which immensely restricts their practical application in multitask intelligent metadevices. Herein, an appealing strategy of the PCM is proposed to realize tunable functions in co-polarized reflection channels of orthogonal circularly polarized waves and in co-polarized and cross-polarized reflection channels of orthogonal linearly polarized waves from 9.0 to 10.5 GHz. In the above six channels, the spin-decoupled programmable meta-atom can achieve high-efficiency reflection and 1-bit digital phase modulation by selecting the specific ON/OFF states of two diodes, and the phase coding sequence of the PCM is dynamically regulated by the field-programmable gate array to generate the desired function. A proof-of-concept prototype is constructed to verify the feasibility of our methodology, and numerous simulation and experimental results are in excellent agreement with the theoretical predictions. This inspiring design opens a new avenue for constructing intelligent metasurfaces with higher serviceability and flexibility, and has tremendous application potential in communication, sensing, and other multifunctional smart metadevices.
Photonics Research
  • Publication Date: May. 26, 2023
  • Vol. 11, Issue 6, 1047 (2023)
Holography, Gratings, and Diffraction
Leaky cavity modes in metasurfaces: a route to low-loss wideband anomalous dispersion
Xiaofeng Wang, Jiafu Wang, Yajuan Han, Mingbao Yan, Yongfeng Li, Tonghao Liu, Hua Ma, and Shaobo Qu
Metasurfaces have provided unprecedented degrees of freedom in manipulating electromagnetic waves upon interfaces. In this work, we first explore the condition of wide operating bandwidth in the view of reflective scheme, which indicates the necessity of anomalous dispersion. To this end, the leaky cavity modes (LCMs) in the meta-atom are analyzed and can make effective permittivity inversely proportional to frequency. Here we employ the longitudinal Fabry–Perot (F-P) resonances and transverse plasmonic resonances to improve the LCMs efficiency. It is shown that the order of F-P resonance can be customized by the plasmonic modes, that is, the F-P cavity propagation phase should match the phase delay of surface currents excited on the meta-atom. The nth order F-P resonance will multiply the permittivity by a factor of n, allowing larger phase accumulation with increasing frequencies and forming nonlinear phase distribution which can be applied in weak chromatic-aberration focusing design. As a proof-of-concept, we demonstrate a planar weak chromatic-aberration focusing reflector with a thickness of λ0/9 at 16.0–21.0 GHz. This work paves a robust way to advanced functional materials with anomalous dispersion and can be extended to higher frequencies such as terahertz, infrared, and optical frequencies.
Photonics Research
  • Publication Date: May. 30, 2023
  • Vol. 11, Issue 6, 1085 (2023)
Imaging Systems, Microscopy, and Displays
Direct observation of longitudinal aberrated wavefields
J. P. Trevino, V. Coello, A. Jaimes-Nájera, C. E. Garcia-Ortiz, S. Chávez-Cerda, and J. E. Gómez-Correa
Rather than focusing on a focal spot, aberrated wavefields spread out over a region. As a wave phenomenon, optical aberrations are analyzed in terms of waves propagating in the 3D space. In this work, we report the observation of 2D longitudinal aberrated wavefields. This observation can be visualized by mapping the intensity distributions of surface plasmon polaritons (SPPs) that propagate on a metal/air interface using leakage radiation microscopy. The orientation of the SPP beam is tweaked by tilting and translating the system to mimic aberrated beams, presenting known Seidel terms: defocus, spherical, coma, and tilt aberration. This approach allows the examination of the longitudinal evolution of aberrated beams in a visual and rapid manner, in contrast to more complicated post-processing reconstructions.
Photonics Research
  • Publication Date: May. 26, 2023
  • Vol. 11, Issue 6, 1015 (2023)
Imaging Systems, Microscopy, and Displays
Physical origin and boundary of scalable imaging through scattering media: a deep learning-based exploration
Xuyu Zhang, Shengfu Cheng, Jingjing Gao, Yu Gan, Chunyuan Song, Dawei Zhang, Songlin Zhuang, Shensheng Han, Puxiang Lai, and Honglin Liu
Imaging through scattering media is valuable for many areas, such as biomedicine and communication. Recent progress enabled by deep learning (DL) has shown superiority especially in the model generalization. However, there is a lack of research to physically reveal the origin or define the boundary for such model scalability, which is important for utilizing DL approaches for scalable imaging despite scattering with high confidence. In this paper, we find the amount of the ballistic light component in the output field is the prerequisite for endowing a DL model with generalization capability by using a “one-to-all” training strategy, which offers a physical meaning invariance among the multisource data. The findings are supported by both experimental and simulated tests in which the roles of scattered and ballistic components are revealed in contributing to the origin and physical boundary of the model scalability. Experimentally, the generalization performance of the network is enhanced by increasing the portion of ballistic photons in detection. The mechanism understanding and practical guidance by our research are beneficial for developing DL methods for descattering with high adaptivity.
Photonics Research
  • Publication Date: May. 26, 2023
  • Vol. 11, Issue 6, 1038 (2023)
Imaging Systems, Microscopy, and Displays
Real-time noise-free inline self-interference incoherent digital holography with temporal geometric phase multiplexing
Kihong Choi, Jae-Won Lee, Jungyeop Shin, Keehoon Hong, Joongki Park, and Hak-Rin Kim
In this paper, we propose a real-time incoherent digital holographic (IDH) recording system free from bias and twin-image noises. A motionless three-step polarization-encoded phase-shifter operating at 99 Hz is realized with two electrically controllable birefringence-mode liquid crystal cells operating in tandem with a geometric phase lens and polarizers. Based on the proposed optical configuration, a coaxial straight-line self-interference IDH recording system is devised. Notably, the elimination of bias and twin-image noise from three phase-shifted images is demonstrated as a proof of concept. Moreover, complex-valued holographic video acquisitions with a resolution greater than 20 megapixels are demonstrated, with an effective acquisition frequency of 33 Hz.
Photonics Research
  • Publication Date: May. 04, 2023
  • Vol. 11, Issue 6, 906 (2023)
Integrated Optics
High-speed integrated QKD system
Rebecka Sax, Alberto Boaron, Gianluca Boso, Simone Atzeni, Andrea Crespi, Fadri Grünenfelder, Davide Rusca, Aws Al-Saadi, Danilo Bronzi, Sebastian Kupijai, Hanjo Rhee, Roberto Osellame, and Hugo Zbinden
Quantum key distribution (QKD) is nowadays a well-established method for generating secret keys at a distance in an information-theoretically secure way, as the secrecy of QKD relies on the laws of quantum physics and not on computational complexity. In order to industrialize QKD, low-cost, mass-manufactured, and practical QKD setups are required. Hence, photonic and electronic integration of the sender’s and receiver’s respective components is currently in the spotlight. Here we present a high-speed (2.5 GHz) integrated QKD setup featuring a transmitter chip in silicon photonics allowing for high-speed modulation and accurate state preparation, as well as a polarization-independent low-loss receiver chip in aluminum borosilicate glass fabricated by the femtosecond laser micromachining technique. Our system achieves raw bit error rates, quantum bit error rates, and secret key rates equivalent to a much more complex state-of-the-art setup based on discrete components [BoaronA.et al., Phys. Rev. Lett.121, 190502 (2018)].
Photonics Research
  • Publication Date: May. 25, 2023
  • Vol. 11, Issue 6, 1007 (2023)
Nanophotonics and Photonic Crystals
Transport of a topologically protected photonic waveguide on-chip
Sai Yan, Jingnan Yang, Shushu Shi, Zhanchun Zuo, Can Wang, and Xiulai Xu
We propose a design on integrated optical devices on-chip with an extra width degree of freedom by using a photonic crystal waveguide with Dirac points between two photonic crystals with opposite valley Chern numbers. With such an extra waveguide, we demonstrate numerically that the topologically protected photonic waveguide retains properties of valley-locking and immunity to defects. Due to the design flexibility of the width-tunable topologically protected photonic waveguide, many unique on-chip integrated devices have been proposed, such as energy concentrators with a concentration efficiency improvement of more than one order of magnitude, and a topological photonic power splitter with an arbitrary power splitting ratio. The topologically protected photonic waveguide with the width degree of freedom could be beneficial for scaling up photonic devices, and provides a flexible platform to implement integrated photonic networks on-chip.
Photonics Research
  • Publication Date: May. 26, 2023
  • Vol. 11, Issue 6, 1021 (2023)
Nanophotonics and Photonic Crystals
Manipulation of polarization topology using a Fabry–Pérot fiber cavity with a higher-order mode optical nanofiber
Maki Maeda, Jameesh Keloth, and Nic Chormaic
Optical nanofiber cavity research has mainly focused on the fundamental mode. Here, a Fabry–Pérot fiber cavity with an optical nanofiber supporting the higher-order modes (TE01, TM01, HE21o, and HE21e) is demonstrated. Using cavity spectroscopy, with mode imaging and analysis, we observed cavity resonances that exhibited complex, inhomogeneous states of polarization with topological features containing Stokes singularities such as C-points, Poincaré vortices, and L-lines. In situ tuning of the intracavity birefringence enabled the desired profile and polarization of the cavity mode to be obtained. We believe these findings open new research possibilities for cold atom manipulation and multimode cavity quantum electrodynamics using the evanescent fields of higher-order mode optical nanofibers.
Photonics Research
  • Publication Date: May. 26, 2023
  • Vol. 11, Issue 6, 1029 (2023)
Nanophotonics and Photonic Crystals
Topological large-area one-way transmission in pseudospin-field-dependent waveguides using magneto-optical photonic crystals
Xinyue Yu, Jianfeng Chen, Zhi-Yuan Li, and Wenyao Liang
We propose a pseudospin-field-dependent waveguide (PFDW) by constructing a sandwiched heterostructure consisting of three magneto-optical photonic crystals (MOPCs) with different geometric parameters. The upper expanded MOPC applied with an external magnetic field has broken time-reversal symmetry (TRS) and an analogous quantum spin Hall (QSH) effect, while the middle standard and the lower compressed ones are not magnetized and trivial. Attributed to the TRS-broken-QSH effect of the upper MOPC, the topological large-area one-way transmission that uniformly distributes over the middle domain is achieved and exhibits the characteristics of a pseudospin-field-momentum-locking; i.e., pseudospin-down (or pseudospin-up) leftward (or rightward) waveguide state when the positive (or negative) magnetic field is applied on the upper MOPC. We further demonstrate the strong robustness of the PFDW against backscattering from various kinds of defects. In addition, a topological beam modulator that can compress or expand the light beam, and a large-area pseudospin beam splitter have been designed. These results have potential in various applications such as sensing, signal processing, and optical communications.
Photonics Research
  • Publication Date: May. 30, 2023
  • Vol. 11, Issue 6, 1105 (2023)
Nonlinear Optic
Hyperbolic resonant radiation of concomitant microcombs induced by cross-phase modulation
Yang Wang, Weiqiang Wang, Zhizhou Lu, Xinyu Wang, Long Huang, Brent E. Little, Sai T. Chu, Wei Zhao, and Wenfu Zhang
A high-quality optical microcavity can enhance optical nonlinear effects by resonant recirculation, which provides a reliable platform for nonlinear optics research. When a soliton microcomb and a probe optical field are coexisting in a micro-resonator, a concomitant microcomb (CMC) induced by cross-phase modulation (XPM) will be formed synchronously. Here, we characterize the CMC comprehensively in a micro-resonator through theory, numerical simulation, and experimental verification. It is found that the CMCs spectra are modulated due to resonant radiation (RR) resulting from the interaction of dispersion and XPM effects. The group velocity dispersion induces symmetric RRs on the CMC, which leads to a symmetric spectral envelope and a dual-peak pulse in frequency and temporal domains, respectively, while the group velocity mismatch breaks the symmetry of RRs and leads to asymmetric spectral and temporal profiles. When the group velocity is linearly varying with frequency, two RR frequencies are hyperbolically distributed about the pump, and the probe light acts as one of the asymptotic lines. Our results enrich the CMC dynamics and guide microcomb design and applications such as spectral extension and dark pulse generation.
Photonics Research
  • Publication Date: May. 30, 2023
  • Vol. 11, Issue 6, 1075 (2023)
Optical and Photonic Materials
Blue perovskite single-mode lasing in a rubidium lead bromide microcubic cavity
Bo Li, Wangqi Mao, Shuang Liang, Yifeng Shi, Hongxing Dong, and Long Zhang
Lead halide perovskite microlasers have shown impressive performance in the green and red wavebands. However, there has been limited progress in achieving blue-emitting perovskite microlasers. Here, blue-emitting perovskite-phase rubidium lead bromide (RbPbBr3) microcubes were successfully prepared by using a one-step chemical vapor deposition process, which can be utilized to construct optically pumped whispering gallery mode microlasers. By regulating the growth temperature, we found that a high-temperature environment can facilitate the formation of the perovskite phase and microcubic morphology of RbPbBr3. Notably, blue single-mode lasing in a RbPbBr3 microcubic cavity with a narrow linewidth of 0.21 nm and a high-quality factor (2200) was achieved. The obtained lasing from RbPbBr3 microlasers also exhibited an excellent polarization state factor (0.77). By modulating the mixed-monovalent cation composition, the wavelength of the microlaser could be tuned from green (536 nm) to pure blue (468 nm). Additionally, the heat stability of the mix-cation perovskite was better than that of conventional CsPbBr3. The stable and high-performance blue single-mode microlasers may thus facilitate the application of perovskite lasers in blue laser fields.
Photonics Research
  • Publication Date: May. 30, 2023
  • Vol. 11, Issue 6, 1067 (2023)
Silicon Photonics
Inverse design of a Si-based high-performance vertical-emitting meta-grating coupler on a 220 nm silicon-on-insulator platform
Jinhyeong Yoon, Jae-Yong Kim, Junhyeong Kim, Hyeonho Yoon, Berkay Neşeli, Hyo-Hoon Park, and Hamza Kurt
Efficient extraction of light from a high refractive index silicon waveguide out of a chip is difficult to achieve. An inverse design approach was employed using the particle swarm optimization method to attain a vertical emitting meta-grating coupler with high coupling efficiency in a 220-nm-thick silicon-on-insulator platform. By carefully selecting the figure of merit and appropriately defining parameter space, unique L-shape and U-shape grating elements that boosted the out-of-plane radiation of light were obtained. In addition, a 65.7% (-1.82 dB) outcoupling efficiency and a 60.2% (-2.2 dB) fiber-to-chip vertical coupling efficiency with an 88 nm 3 dB bandwidth were demonstrated by numerical simulation. Considering fabrication constraints, the optimized complex meta-grating coupler was modified to correspond to two etching steps and was then fabricated with a complementary metal-oxide-semiconductor-compatible process. The modified meta-grating coupler exhibited a simulated coupling efficiency of 57.5% (-2.4 dB) with a 74 nm 3-dB bandwidth in the C-band and an experimentally measured coupling efficiency of 38% (-4.2 dB).
Photonics Research
  • Publication Date: May. 04, 2023
  • Vol. 11, Issue 6, 897 (2023)
Ultrafast Optics
Promoting spintronic terahertz radiation via Tamm plasmon coupling
Yunqing Jiang, Hongqing Li, Xiaoqiang Zhang, Fan Zhang, Yong Xu, Yongguang Xiao, Fengguang Liu, Anting Wang, Qiwen Zhan, and Weisheng Zhao
Spectral fingerprint and terahertz (THz) field-induced carrier dynamics demands the exploration of broadband and intense THz signal sources. Spintronic THz emitters (STEs), with high stability, a low cost, and an ultrabroad bandwidth, have been a hot topic in the field of THz sources. One of the main barriers to their practical application is lack of an STE with strong radiation intensity. Here, through the combination of optical physics and ultrafast photonics, the Tamm plasmon coupling (TPC) facilitating THz radiation is realized between spin THz thin films and photonic crystal structures. Simulation results show that the spectral absorptance can be increased from 36.8% to 94.3% for spin THz thin films with TPC. This coupling with narrowband resonance not only improves the optical-to-spin conversion efficiency, but also guarantees THz transmission with a negligible loss (4%) for the photonic crystal structure. According to the simulation, we prepared this structure successfully and experimentally realized a 264% THz radiation enhancement. Furthermore, the spin THz thin films with TPC exhibited invariant absorptivity under different polarization modes of the pump beam and weakening confinement on an obliquely incident pump laser. This approach is easy to implement and offers possibilities to overcome compatibility issues between the optical structure design and low energy consumption for ultrafast THz opto-spintronics and other similar devices.
Photonics Research
  • Publication Date: May. 26, 2023
  • Vol. 11, Issue 6, 1057 (2023)