Refractive index sensing based on twisted nano-kirigami metasurface

Shuqi Qiao, Xiaochen Zhang, Qinghua Liang, Yang Wang, Changyin Ji, Xiaowei Li, Lan Jiang, Shuai Feng, Honglian Guo, and Jiafang Li

DOI: 10.1364/PRJ.507863 Received 12 Oct 2023; Accepted 21 Nov 2023; Posted 21 Nov 2023  View: PDF

Abstract: Plasmonic sensing technology has attracted considerable attention for high sensitivity due to the ability to effectively localize and manipulate light. In this study, we demonstrate a refractive index (RI) sensing scheme based on open-loop twisted meta-molecule arrays using the versatile nano-kirigami principle. The RI sensing has feature of small footprint, flexible control, and simple preparation. By engineering the morphology of meta-molecules or the RI of the ambient medium, the chiral surface lattice resonances (SLRs) can be significantly enhanced, and the wavelength, intensity, and sign of circular dichroism (CD) can be flexibly tailored. Utilizing the relation between the wavelength of the CD peak and the RI of the superstrate, the RI sensor achieves a sensitivity of 1133 nm/RIU. Additionally, we analyze these chiroptical responses by performing electromagnetic multipolar decomposition and electric field distributions. Our study may serve as an ideal platform for applications of RI measurement and provide new insights into the manipulation of chiral light-matter interactions.

Impact of doping profile on the formation of laser-active centers in bismuth-doped GeO₂ – SiO₂ glass fibers

Sergey Alyshev, Alexander Vakhrushev, Aleksandr Khegai, Elena Firstova, Konstantin Riumkin, Mikhail Melkumov, Lyudmila Ishakova, Andrey Umnikov, and Sergey Firstov

DOI: 10.1364/PRJ.498782 Received 05 Jul 2023; Accepted 20 Nov 2023; Posted 21 Nov 2023  View: PDF

Abstract: Multi-wavelength-band transmission technology based on the exploitation of the extended spectral region is considered as a potential approach to increase the transmission capacity in the deployed fiber-optic communication infrastructure. The development of optical amplifiers operating in O-, E-, S- and U-telecom bands is an extremely important challenge for the successful implementation of this technology. Bismuth-doped fibers are of increasing interest as gain materials, which can be used to provide broadband amplification in the mentioned telecom bands. This is due to the ability of Bi ions incorporated into glass network to form bismuth active centers (BACs) with specific optical properties, which are primarily determined by the glass modifiers. In this work, the impact of the doping profiles of both Ge atoms as glass modifiers and Bi ions on the BACs formation is studied using a series of bismuth-doped fibers fabricated by MCVD technique. The Bi-to-BACs conversion efficiency in various spatial regions of the studied samples is presented. It is turned out that for high-Bi concentration regions, the conversion efficiency is very low(less than 10%). In addition, the relationship of the conversion efficiency to the distribution of Bi ions and/or Ge atoms is discussed. Finally, a continuous-wave laser at 1.46 µm with a record slope efficiency of 80% is demonstrated using a Bi-doped fiber with confined doping profile, where the Bi-to-BACs conversion efficiency is 35%. This paper provides new information, which might help to facilitate understanding of the features of Bi-doped fibers and their potentially achievable characteristics.

Mutual aid instead of mutual restrain： Interactive probing for topological charge and phase of a vortex beam of large aberrations

Shengyang Wu, Benli Yu, and Zhang Lei

DOI: 10.1364/PRJ.498502 Received 26 Jun 2023; Accepted 15 Nov 2023; Posted 16 Nov 2023  View: PDF

Abstract: An imperfect propagation environment or optical system would introduce wavefront aberrations to vortex beams. The phase aberrations and orbital angular momentum in a vortex beam are proved to be mutually restrictive in parameter measurement. Aberrations make traditional topological charge (TC) probing methods ineffective while the phase singularity makes phase retrieval difficult due to the aliasing between the wrapped phase jump and the vortex phase jump. An interactive probing method is proposed to make measurements of the aberrated phase and orbital angular momentum in a vortex beam assist rather than hinder each other. The phase unwrapping is liberated from the phase singularity by an annular shearing interference technique while the TC value is determined by a Moiré technique immune to aberrations. Simulation and experimental results proving the method effective are presented. It is of great significance to judge the characteristics of vortex beams passing through non-ideal environments and optical systems.

High-responsivity on-chip waveguide coupled germanium photodetector for 2-µm waveband

Jianing Wang, Xi Wang, Yihang Li, Yanfu Yang, Qinghai Song, and Ke Xu

DOI: 10.1364/PRJ.508024 Received 12 Oct 2023; Accepted 15 Nov 2023; Posted 16 Nov 2023  View: PDF

Abstract: Recently, the emerging 2-µm waveband has gained increasing interests due to its great potential for a wide scope of applications. Compared with the existing optical communication windows at shorter wavelengths, it also offers distinct advantages of lower nonlinear absorption, better fabrication tolerance and larger free carrier plasma effect for silicon photonics, which has been a proven device technology. While much progress has been witnessed for silicon photonics at 2-μm waveband, the primary challenge still exists for on-chip detectors. Despite the maturity and compatibility of the waveguide coupled photodetectors made of germanium, the 2-μm regime is far beyond its cut-off wavelength. In this work, we demonstrate an efficient and high-speed on-chip waveguide-coupled germanium photodetector operating at the 2-µm waveband. The weak sub-bandgap absorption of epitaxial germanium is greatly enhanced by a lateral separation absorption charge multiplication structure. The detector is fabricated by standard process offered by a commercial foundry. The device has a benchmark performance with responsivity of 1.05 A/W and 3 dB-bandwidth of 7.12 GHz which is able to receive high-speed signals with up to 20 Gbit/s data rate. The availability of such efficient and fast on-chip detector circumvents the barriers between silicon photonic integrated circuits and the potential applications at 2-μm waveband.

Indium-Doped Perovskite-Related Cesium Copper Halide Scintillator Films for High-Performance X-ray Imaging

Rui Liu, Zhiyong Liu, Chengxu Lin, Guangda Niu, Xuning Zhang, Bo Sun, tilin shi, and Guanglan Liao

DOI: 10.1364/PRJ.501477 Received 29 Aug 2023; Accepted 14 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: Scintillators are widely utilized in high-energy radiation detection in view of their high light yield and short fluorescence decay time. However, constrained by their current shortcomings, such as complex fabrication procedures, high-temperature, and difficulty in large-scale, traditional scintillators are difficult to meet the increasingly demand for cost-effective, flexible, and environment-friendly X-ray detection. Perovskite-related cesium copper halide scintillators have recently got multitudinous research due to their tunable emission wavelength, high photoluminescence quantum yield (PLQY), and excellent optical properties. Herein, we demonstrated a facile solution-synthesis route for indium-doped all-inorganic cesium copper iodide (Cs3Cu2I5) powders and a high scintillation yield flexible film utilizing indium doped Cs3Cu2I5 powders. The large area flexible films achieved a PLQY as high as 90.2% by appropriately adjusting the indium doping concentration, much higher than the undoped one (73.9%). Moreover, benefiting from low self-absorption and high PLQY, the Cs3Cu2I5: In films exhibited ultralow detection limit of 56.2 nGy/s, high spatial resolution up to 11.3 lp/mm, and marvellous relative light output with tremendous stability, facilitating Cs3Cu2I5: In films the excellent candidates for X-ray medical radiography. Our work provides an effective strategy for developing environment-friendly, low-cost, and efficient scintillator films, showing great potential in the application of high-performance X-ray imaging.

10 Gb/s classical secure key distribution based on temporal steganography and private chaotic phase scrambling

Zhensen Gao, Zhitao Deng, Lihong Zhang, Xulin Gao, Yuehua An, Anbang Wang, Songnian Fu, Zhaohui Li, Yuncai Wang, and Yuwen Qin

DOI: 10.1364/PRJ.502992 Received 09 Aug 2023; Accepted 13 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: Secure distribution of high speed digital en/decryption keys over a classical fiber channel is strongly pursed for realizing perfect secrecy communication systems. However, it is still challenging to achieve a secret key rate in the order of gigabit per second to be comparable with the bit rate of commercial fiber-optic systems. In this paper, we propose and experimentally demonstrate a novel solution for high-speed secure key distribution based on temporal steganography and private chaotic phase scrambling in the classical physical layer. The encryption key is temporally concealed into the background noise in the time domain and randomly phase scrambled bit-by-bit by a private chaotic signal, which provides two layers of enhanced security to guarantee the privacy of key distribution whilst providing a high secret key rate. We experimentally achieved a record classical secret key rate of 10 Gb/s with a bit error rate lower than the hard-decision forward error correction (HD-FEC) over a 40-km standard single mode fiber. The proposed solution holds great promise for achieving high-speed key distribution in the classical fiber channel by combining steganographic transmission and chaotic scrambling.

Ultra-compact silicon on-chip polarization controller

weike zhao, Yingying Peng, Mingyu Zhu, Ruoran Liu, Xiaolong Hu, Yaocheng Shi, and Daoxin Dai

DOI: 10.1364/PRJ.499801 Received 07 Jul 2023; Accepted 13 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: On-chip polarization controllers are extremely important for various optical systems. In this paper, a concise and robust silicon-based on-chip polarization controller is proposed and demonstrated by integrating a special polarization converter and phase shifters. The special polarization converter consists of a 1 × 1 Mach-Zehnder interferometer (MZI) with two polarization-dependent mode converters (PDMCs) at the input/output ends. When light with an arbitrary state of polarization (SOP) is launched into the chip, the TE0 and TM0 modes are simultaneously excited. The polarization extinction ratio (PER) and the phase difference for the TE0/TM0 modes are tuned by controlling the first phase-shifter, the polarization converter, and the second phase-shifter. As a result, one can reconstruct the light SOP at the output port. The fabricated polarization controller, as compact as ~ 150 × 700 μm2, exhibits an excess loss (EL) of less than 1 dB and a PER range of 43.5 dB for arbitrary input light beams.

Fully-Integrated and Broadband Si-Rich Silicon Nitride Wavelength Converter Based on Bragg Scattering Intermodal Four-Wave Mixing

Valerio Vitali, Thalía Domínguez Bucio, Hao Liu, José Luque-González, Francisco Jurado-Romero, Alejandro Ortega-Moñux, Glenn Churchill, James Gates, James Hillier, Nikolaos Kalfagiannis, Daniele Melati, Jens Schmid, Ilaria Cristiani, Pavel Cheben, J. Gonzalo Wangüemert-Pérez, I. Molina-Fernández, Frederic Gardes, Cosimo Lacava, and Periklis Petropoulos

DOI: 10.1364/PRJ.506691 Received 22 Sep 2023; Accepted 13 Nov 2023; Posted 21 Nov 2023  View: PDF

Abstract: Intermodal four-wave mixing (FWM) processes have recently attracted significant interest for all-optical signal processing applications thanks to the possibility to control the propagation properties of waves exciting distinct spatial modes of the same waveguide. This allows, in principle, to place signals in different spectral regions and satisfy the phase matching condition over considerably larger bandwidths compared to intramodal processes. However, the demonstrations reported so far have shown a limited bandwidth and suffered from the lack of on-chip components designed for broadband manipulation of different modes. We demonstrate here a silicon-rich silicon nitride wavelength converter based on Bragg scattering intermodal FWM, which integrates mode conversion, multiplexing and de-multiplexing functionalities on-chip. The system enables wavelength conversion between pump waves and a signal located in different telecommunication bands (separated by 60 nm) with a 3dB bandwidth exceeding 70 nm, which represents the widest bandwidth ever achieved in an intermodal FWM-based system.

Dynamic Multifunctional Metasurfaces: Inverse Design Deep Learning Approach

zd Lei, Xu yi duo, Cheng Lei, Zhao Yan, and Du Wang

DOI: 10.1364/PRJ.505991 Received 15 Sep 2023; Accepted 12 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: Optical metasurfaces (OMs) offer unprecedented control over electromagnetic waves, enabling advanced optical multiplexing. The emergence of deep learning has opened new avenues for designing OMs. However, existing deep learning methods for OMs primarily focus on forward design, which limits their design capabilities, lacks global optimization, and relies on prior knowledge. Additionally, most OMs are static, with fixed functionalities once processed. To overcome these limitations, we propose an inverse design deep learning method for dynamic OMs. Our approach comprises a forward prediction network and an inverse retrieval network. The forward prediction network establishes a mapping between meta-unit structure parameters and reflectance spectra. The inverse retrieval network generates a library of meta-unit structure parameters based on target requirements, enabling end-to-end design of OMs. By incorporating the dynamic tunability of the phase change material Sb2Te3 with inverse design deep learning, we achieve the design and verification of dynamic multifunctional OMs. Our results demonstrate OMs with multiple information channels and encryption capabilities that can realize multiple physical field optical modulation functions. When Sb2Te3 is in the amorphous state, near-field nano-printing based on meta-unit amplitude modulation is achieved for X-polarized incident light, while holographic imaging based on meta-unit phase modulation is realized for circularly polarized light. In the crystalline state, the encrypted information remains secure even with the correct polarization input, achieving double encryption. This research points towards ultra-compact, high-capacity, and highly secure information storage approaches.

Dual-microcomb generation via a monochromatically pumped dual-mode microresonator

runlin miao, Ke Yin, Chao Zhou, chenxi zhang, zhuopei Yu, Xin Zheng, and Tian Jiang

DOI: 10.1364/PRJ.507227 Received 29 Sep 2023; Accepted 11 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: Microcombs have enabled a host of cutting-edge applications from metrology to communications, that have garnered significant attention in the last decade. Nevertheless, due to the thermal instability of the microresonater, additional control devices like auxiliary lasers are indispensable for single soliton generation in some scenarios. Specifically, the increased system complexity would be too overwhelming for dual-microcomb generation. Here, we put forward a novel approach to mitigate the thermal instability and generate the dual-microcomb using a compact system. This process is akin to mode-division multiplexing, as the dual-microcomb are generated by pumping the dual-mode of a single Si3N4 microresonator with a continuous-wave laser. Both numerical simulations and experimental measurements indicate that this innovative technique could offer a straightforward way to enlarge the soliton existence range, allowing entry into the multistability regime and triggering another microcomb alongside the main soliton pulse. This outcome not only shines new light on the interaction mechanism of microresonator modes, but also provides an avenue for the development of dual-microcomb based ranging and low phase noise microwave generation.

Generating a nanoscale blade-like optical field in a coupled nanofiber pair

Yuxin Yang, Jiaxin Gao, Hao Wu, Zhanke Zhou, Liu Yang, Xin Guo, Pan Wang, and Limin Tong

DOI: 10.1364/PRJ.506681 Received 22 Sep 2023; Accepted 10 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: Optical field with sub-nm confinement is essential to explore atomic- or molecular-level light-matter interaction. While such fields demonstrated so far have typically point-like cross sections, an optical field having higher-dimensional cross section may offer higher flexibility and/or efficiency in applications. Here, we propose to generate a nanoscale blade-like optical field in a coupled nanofiber pair (CNP) with a 1-nm-width central slit. Based on a strong mode coupling-enabled slit waveguide mode, a sub-nm-thickness blade-like optical field can be generated with a cross-section down to ~0.28×38 nm² at 1550-nm wavelength (i.e., a thickness of ~λ₀/5000,) and a peak to background intensity ratio (PBR) higher than 20 dB. The slit waveguide mode of the CNP can be launched from one of the two nanofibers that is connected to a standard optical fiber via an adiabatical fiber taper, in which a fundamental waveguide mode of the fiber can be converted into a high-purity slit mode with high efficiency (>98%) within a CNP length of less than 10 μm at 1550 nm wavelength. The wavelength-dependent behaviors and group velocity dispersion in mode converting processes are also investigated, showing that such a CNP-based design is also suitable for broadband and ultrafast pulsed operation. Our results may open up new opportunities for studying light-matter interaction down to sub-nm scale, as well as for exploring ultra-high-resolution optical technology ranging from super-resolution nanoscopy to chemical bond manipulation.

Distributed phase-matching measurement for dynamic strain and temperature sensing based on stimulated Brillouin scattering enhanced Four-wave mixing

Yuan Wang, Pedro Tovar, Juntong Yang, Liang Chen, and Xiaoyi Bao

DOI: 10.1364/PRJ.497955 Received 15 Jun 2023; Accepted 08 Nov 2023; Posted 09 Nov 2023  View: PDF

Abstract: Brillouin dynamic grating (BDG) can be used for distributed birefringence measurement in optical fibers, offering high sensitivity and spatial resolution for sensing applications. However, it is quite a challenge to achieve dynamic measurements with both high accuracy and high spatial resolution simultaneously. In this work, we propose a novel sensing mechanism to achieve distributed phase-matching measurement by using a chirped pulse as a probe signal. In BDG reflection, the peak reflection corresponds to the highest Four-wave mixing (FWM) conversion efficiency and Brillouin frequency in fast and slow axis are equal, which is called phase-matching condition in one specific fiber location. This condition changes at different fiber positions which requires a range of frequency injection for the probe wave. The proposed method utilizes chirped pulse as a probe wave to cover this frequency range associated with distributed birefringence inhomogeneity. This allows us to detect distributed phase matching for birefringence changes induced by temperature and strain variations. Thanks to the single-shot and direct time delay measurement capability, the acquisition rate in our system is only limited by the sensor length. Notably, unlike conventional BDG-based systems, the spatial resolution here is determined by both the frequency chirping rate of the probe pulse and the beat length of the fiber. In the experiments, an acquisition rate of 1 kHz (only limited by the fiber length) and a spatial resolution of up to 10 cm with a 20 ns probe pulse width are achieved, and temperature and strain sensing accuracy are up to 5.6 mK and 0.37με.

Single-shot non-line-of-sight imaging based on chromato-axial differential correlography

Lingfeng Liu, Shuo Zhu, Wenjun Zhang, Lianfa Bai, Enlai Guo, and Jing Han

DOI: 10.1364/PRJ.501597 Received 26 Jul 2023; Accepted 08 Nov 2023; Posted 09 Nov 2023  View: PDF

Abstract: Non-line-of-sight (NLOS) imaging is a challenging task aimed at reconstructing objects outside the direct view of the observer. Nevertheless, traditional NLOS imaging methods typically rely on intricate and costly equipment to scan and sample the hidden object. These methods often suffer from restricted imaging resolution and require high system stability. Herein, we propose a single-shot high-resolution NLOS imaging method via chromato-axial differential correlography, which adopts low-cost continuous-wave lasers and a conventional camera. By leveraging the uncorrelated laser speckle patterns along the chromato-axis, this method can reconstruct hidden objects of diverse complexity with sub-millimeter resolution using only one exposure measurement. The achieved background stability through single-shot acquisition, along with the inherent information redundancy in the chromato-axial differential speckles, enhances the robustness of the system against vibration and colored stain interference.This approach overcomes the limitations of conventional methods by simplifying the sampling process, improving system stability, and achieving enhanced imaging resolution using available equipment. This work serves as a valuable reference for the real-time development and practical implementation of NLOS imaging.

From Non-scattering to Super-scattering with Mie-Tronics

Hooman Barati Sedeh and Natalia Litchinitser

DOI: 10.1364/PRJ.503182 Received 14 Aug 2023; Accepted 08 Nov 2023; Posted 09 Nov 2023  View: PDF

Abstract: Electric anapoles, arising from the destructive interference of primitive and toroidal electric dipole moments, have recently emerged as a fundamental class of non-scattering sources. On the other hand, super-scattering states represent the opposite regime wherein the scattering cross-section of a subwavelength particle exceeds the single-channel limit, leading to a strong scattering behavior. In this work, we demonstrate that the interplay between the topology of light and the subwavelength scatterer could result in two opposite regimes of light-matter interaction—a non-scattering hybrid anapole state and a super-scattering regime. In particular, we present the emergence of a new non-scattering state, referred to as hybrid anapole, which surpasses conventional electric dipole anapoles by achieving a remarkable -fold enhancement in the suppression of far-field radiation and almost three-fold enhancement in the confinement of electromagnetic energy inside the meta-atom. We also explore the role of particle orientation and its inversion symmetry on the scattering response and predict the possibility of switching between non-scattering to super-scattering states within the same platform. The presented study elucidates the role of light and matter topologies in the scattering response of subwavelength meta-atoms, uncovering two opposite regimes of light-matter interaction and opening new avenues in applications such as nonlinear optics and spectroscopy.

Passive imaging through dense scattering media

Yaoming Bian, Fei Wang, Yuanzhe Wang, Zhenfeng Fu, Haishan Liu, Haiming Yuan, and Guohai Situ

DOI: 10.1364/PRJ.503451 Received 17 Aug 2023; Accepted 06 Nov 2023; Posted 14 Nov 2023  View: PDF

Abstract: Imaging through non-static scattering media such as dense fog, heavy smoke, and turbid water is crucial in various applications. However, most existing methods rely on either active light illumination or image priors, preventing their application in situations where only passive illumination is possible. This study presents a universal passive imaging method through dense scattering media that do not depend on any prior assumptions. Combining the selection of small-angle components out of the incoming information-carrying scattering light and image enhancement algorithm that incorporates time-domain minimum filtering and denoising, we show that the proposed method can dramatically improve the signal-to-interference ratio and contrast of the raw camera image in outfield experiments.

Electron-beam-driven anomalous Doppler effects in Smith–Purcell radiation

Xiaoqiuyan Zhang, Tianyu Zhang, Zhuocheng Zhang, Xingxing Xu, Diwei Liu, Zhaoyun Duan, Yanyu Wei, Yubin Gong, Liang Jie Wong, and Min Hu

DOI: 10.1364/PRJ.505819 Received 13 Sep 2023; Accepted 02 Nov 2023; Posted 09 Nov 2023  View: PDF

Abstract: The interaction between electrons and matter is an effective means of light emission, through mechanisms including Cherenkov radiation and Smith–Purcell radiation (SPR). In this study, we show that the inverse superlight Doppler effects can be realized in reverse Smith-Purcell radiation excited by free electron beam with a homogeneous substrate. In particular, we find that two types of anomalous SPR exist in the homogenous substrate: special SPR and reverse SPR. Our results reveal that the electron velocity can be tuned to simultaneously excite different combinations of normal SPR, special SPR and reverse SPR. The proposed manifold light radiation mechanism can offer greater versatility in controlling and shaping SPR.

Flexible tuning of multifocal holographic imaging based on electronically controlled metasurfaces

Bowen Zeng, Chenxia Li, Bo Fang, Zhi Hong, and Xufeng Jing

DOI: 10.1364/PRJ.506885 Received 28 Sep 2023; Accepted 02 Nov 2023; Posted 06 Nov 2023  View: PDF

Abstract: Programmable hyper-coded holography has the advantage of being programmable as well as being flexibly modifiable. Digitally coded metamaterials with excellent electromagnetic modulation capability and the ability to control the phase to modulate the spatial radiation field through external excitation in the form of switching can be used to realize low-cost digital arrays. We design a 1-bit encoded programmable metasurface, which is electrically connected to control the PIN diode in the switching state, and to switch the condition of each metasurface cell between "0" and "1". Using the designed programmable metasurface, we can randomly encode the cell structure to realize single-focus focusing, multi-focusing and simple holographic letter imaging. Based on the nonlinear holographic model, we employ the Gerchberg-Saxton improvement algorithm to modulate the energy distribution at the focus by adjusting the phase distribution. Importantly, we introduce the Fourier convolution principle to regulate the holographic imaging focus flexibly.

Direct amplification of femtosecond optical vortices in a single-crystal fiber

Changsheng Zheng, Tianyi Du, Lei Zhu, Zhanxin Wang, Kangzhen Tian, Yongguang Zhao, Zhiyong Yang, Haohai Yu, and Valentin Petrov

DOI: 10.1364/PRJ.507488 Received 04 Oct 2023; Accepted 31 Oct 2023; Posted 01 Nov 2023  View: PDF

Abstract: Spatially twisted light with femtosecond temporal structure is of particular interest in strong-field physics and light-matter interactions. However, present femtosecond vortex sources exhibit limited power handling capabilities, and their amplification remains an ongoing challenge particularly for high-order orbital angular momentum (OAM) states due to several inherent technical difficulties. Here, we exploit a straightforward approach to directly amplify a femtosecond optical vortex (FOV, OAM = ‒8ħ) by using a two-stage single-crystal fiber (SCF) amplifier system without pulse stretching and compression in the time domain, delivering W, 163-fs pulses at a repetition rate of 1 MHz. The spatial and temporal features are well-conserved during the amplification, as well as the high modal purity (> 96%). The results indicate that the multi-stage SCF amplifier system is particularly suited for direct amplification of high-order FOVs. The generated high-power femtosecond OAM laser beams are expected to help reveal complex physical phenomena in light-matter interactions and pave the way for practical applications in attoscience, laser plasma acceleration and high-dimension micromachining.

Coherence phase spectrum analyzer for randomly fluctuated fractional vortex beam

Zhuoyi Wang, Xingyuan Lu, Jianbo Gao, Xuechun Zhao, Qiwen Zhan, Yangjian Cai, and Chengliang Zhao

DOI: 10.1364/PRJ.499520 Received 03 Jul 2023; Accepted 30 Oct 2023; Posted 01 Nov 2023  View: PDF

Abstract: Fractional vortex beams exhibit a higher degree of modulation dimensions than conventional vortices, thus inheriting superior anti-turbulent transmission properties through the incorporation of additional coherence modulation. However, aliasing the mixed modes induced by coherence degradation makes the quantitative measurement of the topological charge in fractional vortex beams challenging. In this study, a coherence phase spectrum was introduced, and experimental demonstrations to quantitatively determine the fractional topological charge of partially coherent fractional vortex beams were performed. By leveraging the four-dimensional measurement of a partially coherent light field, the source coherence function was inversely reconstructed, and fractional topological charges were determined with high precision by extracting the phase spectrum of the coherence function. Laguerre–Gaussian, elliptical Gaussian, and plane-wave-fraction vortex beams with various degrees of coherence were used to demonstrate measurement precision. The proposed method is applicable to X-rays and electron vortices. It has potential applications in optical encryption, high-capacity optical communication, and quantum entanglement.

Ultra-high Extinction Ratio Optical Pulse Generation with Thin Film Lithium Niobate Modulator for Distributed Acoustic Sensing

Yuan Shen, Xiaoqian Shu, Lingmei Ma, Shaoliang Yu, gengxin chen, Liu Liu, Renyou Ge, Bigeng Chen, and Yunjiang Rao

DOI: 10.1364/PRJ.504867 Received 01 Sep 2023; Accepted 26 Oct 2023; Posted 27 Oct 2023  View: PDF

Abstract: We experimentally demonstrate ultra-high extinction ratio (ER) optical pulse modulation with an electro-optical modulator (EOM) on thin film lithium niobate (TFLN) and its application for fiber optic distributed acoustic sensing (DAS). An interface carrier effect leading to a relaxation-tail response of TFLN EOM is discovered, which can be well addressed by a small compensation component following main driving signal. An ultra-high ER >50 dB is achieved by cancelling out the tailed response during pulse modulation using the EOM based on a cascaded Mach-Zehnder interferometer (MZI) structure. The modulated optical pulses are then utilized as probe light for a DAS system, showing a sensitivity up to -62.9 dB rad/Hz² (7 pε/√Hz) for 2-km single-mode sensing fiber. Spatial crosstalk suppression of 24.9 dB along the fiber is also obtained when the ER is improved from 20 dB to 50 dB, clearly revealing its importance to the sensing performance.

Terahertz metasurface polarization detection employing vortex pattern recognition

Chenglong Zheng, Jingyu Liu, Hui Li, mengguang wang, Huaping Zang, Yan Zhang, and Jian-Quan Yao

DOI: 10.1364/PRJ.506746 Received 25 Sep 2023; Accepted 25 Oct 2023; Posted 25 Oct 2023  View: PDF

Abstract: The manipulation and detection of polarization states play a crucial role in the application of 6G terahertz communication. Nonetheless, the development of compact and versatile polarization detection devices capable of detecting arbitrary polarizations continues to be a challenging endeavor. Here, we demonstrate a novel terahertz polarization detection scheme by performing mode purity analysis and multidimensional analysis of the transmitted vortex field. The power of the proposed polarization recognition is verified by using three polarization trajectories, including linear polarizations, circular polarizations, and elliptical polarizations. Using the reconstructed complete polarization parameters, the detected polarization states are characterized using polarization ellipses, Poincaré sphere and full-Stokes parameters. The experimental results validate the power of this scheme in polarization detection. This scheme holds promise for applications in polarization imaging and terahertz communication.

Amplified spontaneous emission at the band edges of Ag-coated Al nanocone array

Ye Xiang, Yongping Zhai, Jiazhi Yuan, Ke Ren, Xuchao Zhao, Dongda Wu, Junqiao La, Yi Wang, and Wenxin Wang

DOI: 10.1364/PRJ.503656 Received 12 Sep 2023; Accepted 19 Oct 2023; Posted 19 Oct 2023  View: PDF

Abstract: Surface lattice resonances (SLRs) with ultra-narrow linewidth (high quality factor) can enhance light-matter interactions at the nanoscale and modulate the propagating light from emission wavelength, direction to efficiency by photonic band engineering. Therefore, SLRs can be served as an excited candidate to enhance, more importantly, to modulate amplified spontaneous emission (ASE) with more optical parameters. Here, this work presents a system of two-dimensional Ag-coated Al nanocone array (Ag NCA) packaged with Nile Red, a normal ASE with 15-fold enhancement is observed under external driven light. This enhancement fades away, obviously, in the case of off-normal condition, as the optical feedback evolves from the band edges steady state to the propagating state. The ASE of this hybrid plasmonic system expands the possibilities of interaction between light and matter and has great promise for applications in nanolasing, super resolution imaging, and photonic integration circuit.

103 GHz germanium-on-silicon photodiode enabled by an optimized U-shaped electrode

Yang Shi, xiang li, Mingjie Zou, Yu Yu, and Xinliang Zhang

DOI: 10.1364/PRJ.495958 Received 18 May 2023; Accepted 17 Oct 2023; Posted 18 Oct 2023  View: PDF

Abstract: High-performance germanium photodiodes are crucial components in silicon photonic integrated circuits for large-capacity data communication. However, the bandwidths of most germanium photodiodes are limited in the ranges of 50-80 GHz primarily due to the intractable resistance-capacitance parasitic effect. Here, we introduce a unique photocurrent collection strategy to alleviate this issue, reducing the parasitic effect by 40.6% without compromising any other performance. Experimentally, a large bandwidth of 103 GHz, an optical responsivity of 0.95 A/W at 1550 nm and a dark current as low as 1.3 nA are achieved, leading to a record high specific detectivity. This is the first breakthrough to 100 GHz bandwidth among all vertical germanium photodiodes, to the best of our knowledge. Open eye diagrams of 120 Gb/s on-off keying and 200 Gb/s four-level pulse amplitude signals are well received. This work provides a promising solution for chip-based ultra-fast photodetection.

Time-interval Measurement with Linear Optical Sampling at the Femtosecond Level

Dongrui Yu, Ziyang Chen, Xuan Yang, Yunlong Xu, Ziyi Jin, Panxue Ma, Yufei Zhang, Song Yu, Bin Luo, and Hong Guo

DOI: 10.1364/PRJ.498810 Received 26 Jun 2023; Accepted 17 Oct 2023; Posted 18 Oct 2023  View: PDF

Abstract: High-precision time-interval measurement is a fundamental technique in many advanced applications, including time and distance metrology, particle physics, and ultra-precision machining. However, many of these applications are confined by the imprecise time-interval measurement of electrical signals, restricting the performance of the ultimate system to a few picoseconds, which limits ultra-high-precision applications. Here, we demonstrate an optical means of the time-interval measurement of electrical signals that can successfully achieve femtosecond (fs)-level precision. The setup is established using the optical-frequency-comb (OFC)-based linear optical sampling technique to realize timescale-stretched measurement. We achieve the measurement precision of 82 fs for a one-shot measurement and 3.05 fs for the 100-times average with post-processing, which is three orders of magnitude higher than the results of older electrical methods. The high-precision time-interval measurement of electrical signals can substantially improve precision measurement technologies.

Reflection-type surface lattice resonances in all-metal metasurfaces for refractive index sensing

Liye Li, Yifan Ouyang, Lijun Ma, Hongshun Sun, Yusa Chen, Meizhang Wu, Zhi-mei Qi, and Wengang Wu

DOI: 10.1364/PRJ.502199 Received 01 Aug 2023; Accepted 15 Oct 2023; Posted 16 Oct 2023  View: PDF

Abstract: Surface lattice resonance (SLR) is a pretty effective mechanism to realize ultranarrow linewidths in the spectrum. Herein, we proposed and demonstrated reflection-type SLRs in all-metal metasurfaces experimentally, compared with the traditional transmission-type SLR, which can avoid the refractive index (RI) mismatch problem and are more suitable for high-efficiency RI sensing due to direct contact and strong light-matter interaction. The measured SLR linewidth is 13.5 nm influenced by the meta-atom size, which needs a compromise design to keep a balance between the narrow linewidth and noise immunity. Notably, the SLR sensitivity is determined by the lattice period along the polarization direction with regularity, which establishes an intuitive link between structures and optical responses and provides a theoretical guide for metasurface designs. Additionally, incident angle multiplexing will make resonance wavelength redshift or blueshift in the case of orthogonal polarization. The rectangular array metasurface can realize dual SLRs with different sensing performances. Flexibly, the SLR can also be formed by the different meta-atoms and arrays. This research supports SLR multifarious applications involving not only RI sensing but also nonlinear optics, nano-laser, etc.

Spin-decoupled meta-coupler empowered multiplexing and multifunction of guided wave radiation

Bin Fang, Zhizhang Wang, Yantao Li, Jitao Ji, kelei xi, Qing Cheng, Fangzhou Shu, Zhongwei Jin, Zhi Hong, Chunlian Zhan, changyu shen, and Tao Li

DOI: 10.1364/PRJ.503249 Received 14 Aug 2023; Accepted 15 Oct 2023; Posted 16 Oct 2023  View: PDF

Abstract: Employing couplers to convert guided wave into free-space modes and flexibly control their wavefront is one of the key technologies in chip-integrated displays and communications. Traditional couplers are mainly composed of gratings, which have limitations in footprint, bandwidth, as well as controllability. Though resonant/geometric metasurface newly emerges as a promising interface for bridging guided waves with free space ones, it either relies on complex optimizations of multiple parameters, or subjects to the locked phase response of opposite spins, and both of which hinder the functional diversity and practical multiplexing capability. Here, we propose and experimentally demonstrate an alternative with spin-decoupled meta-coupler, simultaneously integrating triple functions of guided wave radiation, polarization demultiplexing and dual-channel wavefront manipulation into a single device. By endowing polarization dependent functionalities into a pure geometric metasurface, the out-coupled left-hand and right-hand circular polarization (LCP and RCP) guided waves intelligently identify the predesigned phase modulation and reconstruct desired wavefronts, like bifocal focusing and holography multiplexing, with polarization extinction ratio over 13.4 dB in experiments. We envision that the robust, broadband and multifunctional meta-coupler could pave a way for the development of versatile multiplexed waveguide-based devices.

Simultaneously enhancing capacity and security in free-space optical chaotic communication utilizing orbital angular momentum

Xiangang Luo, Mingfeng Xu, Mingbo Pu, Mengjie Zhou, jiazheng ding, Shuangcheng Chen, Kun Qiu, Ning Jiang, and Yiqun Zhang

DOI: 10.1364/PRJ.496535 Received 26 May 2023; Accepted 13 Oct 2023; Posted 16 Oct 2023  View: PDF

Abstract: Optical chaotic signals emitted from an external-cavity feedback or injected laser diode enable small-signal information concealment in noise-like carrier for secure optical communications. Due to the chaotic bandwidth limitation resulting from intrinsic relaxation oscillation frequency of lasers, multiplexing of optical chaotic signal, such as wavelength division multiplexing in fiber, is a typical candidate for high-capacity secure application. However, the utilization of the spatial dimension of optical chaos for free-space secure communication has not yet been reported. Here, we experimentally demonstrate a free-space all-optical chaotic communication system that simultaneously enhances transmission capacity and security by orbital angular momentum (OAM) multiplexing. Optical chaotic signals with two different OAM modes totally carrying 20 Gbps on-off keying signals are secretly transmitted over a 2 m free-space link, where the channel crosstalk of OAM modes is less than -20 dB, with the mode spacing no less than 3. The receiver can extract valid information only when capturing approximately 92.5% of the OAM beam and correctly demodulating the corresponding mode. Bit error rate below the 7% hard-decision forward error correction threshold of 3.8×10-3 can be achieved for the intended recipient. Moreover, a simulated weak turbulence is introduced to comprehensively analyze the influence on the system performance, including channel crosstalk, chaotic synchronization, and transmission performance. Our work may inspire structured light application in optical chaos and pave a new way for developing future high-capacity free-space chaotic secure communication systems.

Three-dimensional nanoscale vortex line visualization and chiral nanostructure fabrication of tightly focused multi-vortex beams via direct laser writing

Mengdi Luo, Jisen Wen, Pengcheng Ma, Qiuyuan Sun, Xianmeng Xia, Gangyao Zhan, Zhenyao Yang, Liang Xu, Dazhao Zhu, Cuifang Kuang, and Xu Liu

DOI: 10.1364/PRJ.499405 Received 30 Jun 2023; Accepted 13 Oct 2023; Posted 16 Oct 2023  View: PDF

Abstract: Optical singularity is pivotal in nature and has attracted wide interests from many disciplines nowadays, including optical communication, quantum optics, and biomedical imaging. Visualizing vortex lines formed by phase singularities and fabricating chiral nanostructures using the evolution of vortex lines are of great significance. In this paper, we introduce a promising method based on two-photon polymerization direct laser writing (2PP-DLW) to record the morphology of vortex lines generated by tightly focused multi-vortex beams (MVBs) at the nanoscale. Due to Gouy phase, the singularities of the MVBs rotate around the optical axis and move towards each other when approaching the focus. The propagation dynamics of vortex lines were recorded by 2PP-DLW, which explicitly exhibit the evolution of the phase singularities. Additionally, the MVBs were employed to fabricate stable three-dimensional chiral nanostructures due to the spiral-forward property of the vortex line. Because of the obvious chiral features of the manufactured nanostructures, the strong vortical dichroism is observed when excited by the light carrying orbital angular momentum. A number of applications can be envisioned with these chiral nanostructures, such as optical sensing, chiral separation, and information storage.

Optomechanical feedback cooling of a 5 mm long torsional mode

dianqiang su, Yuan Jiang, Pablo Solano, Luis Orozco, John Lawall, and yanting zhao

DOI: 10.1364/PRJ.487035 Received 06 Feb 2023; Accepted 11 Oct 2023; Posted 11 Oct 2023  View: PDF

Abstract: We report three orders of magnitude optical cooling of the fundamental torsional mode of a 5 mm long, 550 nm diameter optical nanofiber. The rotation of the nanofiber couples to the polarization of guided laser fields. We use a weak laser probe to monitor the rotation, and use feedback to modulate the polarization of an auxiliary drive laser providing torque. Our results present a tool for the optomechanical control of large-scale torsional resonators, with metrological applications and potential implications for studying macroscopic objects in quantum states.

Scalable orthogonal delay-division multiplexed OEO artificial neural network

Andrea Zazzi, Arka Dipta Das, Jeremy Witzens, and Lukas Hüssen

DOI: 10.1364/PRJ.493888 Received 24 Apr 2023; Accepted 09 Oct 2023; Posted 09 Oct 2023  View: PDF

Abstract: We propose a new signaling scheme for on-chip optical-electrical-optical artificial neural networks that utilizes orthogonal delay division multiplexing and pilot-tone based self-homodyne detection. This scheme offers a more efficient scaling of the optical power budget with increasing network complexity. Our simulations, based on a 220 nm SOI silicon photonics technology, suggest that the network can support 31 x 31 neurons, with 961 links and freely programmable weights, using a single 500 mW optical comb and an SNR of 21.3 dB per neuron. Moreover, it features a low sensitivity to temperature fluctuations, ensuring that it can be operated outside of a laboratory environment. We demonstrate the network’s effectiveness in nonlinear equalization tasks by training it to equalize a time-interleaved ADC architecture, achieving an ENOB over 4 over the entire 75 GHz ADC bandwidth. We anticipate that this network architecture will enable broadband and low latency nonlinear signal processing in practical settings such as ultra-broadband data converters and real-time control systems.

Learning imaging mechanism directly from optical microscopy observations

Zehao Wang, Long-Kun Shan, Tong-Tian Weng, Tian-Long Chen, Xiangdong Chen, Zhangyang Wang, Guang-can Guo, and Fang-Wen Sun

DOI: 10.1364/PRJ.488310 Received 22 Feb 2023; Accepted 09 Oct 2023; Posted 16 Oct 2023  View: PDF

Abstract: Optical microscopy image plays an important role in scientific research through the direct visualization of the nanoworld, where the imaging mechanism is described as the convolution of the point spread function (PSF) and emitters. Based on a priori knowledge of the PSF or equivalent PSF, it is possible to achieve more precise exploration of the nanoworld. However, it is an outstanding challenge to directly extract the PSF from microscopy images. Here, with the help of self-supervised learning, we propose a physics-informed masked autoencoder (PiMAE) that enables a learnable estimation of the PSF and emitters directly from the raw microscopy images. We demonstrate our method in synthetic data and real-world experiments with significant accuracy and noise robustness. PiMAE outperforms DeepSTORM and the Richardson-Lucy algorithm in synthetic data tasks with an average improvement of 19.6% and 50.7% (35 tasks), respectively, as measured by the normalized root mean square error (NRMSE) metric. This is achieved without prior knowledge of the PSF, in contrast to the supervised approach used by DeepSTORM and the known PSF assumption in the Richardson-Lucy algorithm. Our method, PiMAE, provides a feasible scheme for achieving the hidden imaging mechanism in optical microscopy and has the potential to learn hidden mechanisms in many more systems.

Fano Resonance Enhanced Si/MoS₂ Photodetector

Tianxun Gong, Boyuan Yan, Taiping Zhang, Wen huang, Yuhao He, Xiaoyu Xu, Song Sun, and Xiaosheng Zhang

DOI: 10.1364/PRJ.500883 Received 18 Jul 2023; Accepted 08 Oct 2023; Posted 16 Oct 2023  View: PDF

Abstract: In this work, a Si/MoS₂ heterojunction photodetector enhanced by hot electron injection through Fano resonance is developed. By preparing Au oligomers using capillary-assisted particle assembly (CAPA) on the silicon substrate with nano-hole array, and covering few-layer MoS₂ with Au electrodes on top of the oligomer structure, the Fano resonance couples with Si/MoS₂ Heterojunction. With on-resonance excitation, Fano resonance generated a large number of hot electrons on the surface of oligomers and the hot electrons were injected into MoS₂, providing increased current in the photodetector under a bias voltage. The photodetectors exhibit broadband photoresponse ranging from 450 to 1064 nm, large responsivity up to 52 A/W at wavelength of 785 nm under a bias voltage of 3 V. The demonstrated Fano resonance enhanced Si/MoS₂ heterojunction photodetector provides a strategy to improve the photo responsivity of the two-dimensional materials based photodetectors for optoelectronic applications in the field of visible–near-infrared detection.

Lensless polarimetric coded ptychography for high-resolution, high-throughput gigapixel birefringence imaging on a chip

Liming Yang, Ruihai Wang, Qianhao Zhao, Pengming Song, Shaowei Jiang, Tianbo Wang, Xiaopeng Shao, Chengfei Guo, Rishikesh Pandey, and Guoan Zheng

DOI: 10.1364/PRJ.504378 Received 29 Aug 2023; Accepted 07 Oct 2023; Posted 11 Oct 2023  View: PDF

Abstract: Polarimetric imaging provides valuable insights into the polarization state of light interacting with a sample. It can infer crucial birefringence properties of specimens without using any labels, thereby facilitating the diagnosis of diseases such as cancer and osteoarthritis. In this study, we present a novel polarimetric coded ptychography (pol-CP) approach that enables high-resolution, high-throughput gigapixel birefringence imaging on a chip. Our platform deviates from traditional lens-based systems by employing an integrated polarimetric coded sensor for lensless coherent diffraction imaging. Utilizing Jones calculus, we quantitatively determine the birefringence retardance and orientation information of bio-specimens from the recovered images. Our portable pol-CP prototype can resolve the 435-nm linewidth on the resolution target and the imaging field of view for a single acquisition is limited only by the detector size of 41 mm². The prototype allows for the acquisition of gigapixel birefringence images with a 180-mm² field of view in ~3.5 minutes, a performance that rivals high-end whole slide scanner but at a small fraction of the cost. To demonstrate its biomedical applications, we perform high-throughput imaging of malaria-infected blood smears, locating parasites using birefringence contrast. We also generate birefringence maps of label-free thyroid smears to identify thyroid follicles. Notably, the recovered birefringence maps emphasize the same regions as autofluorescence images, underscoring the potential for rapid on-site evaluation of label-free biopsies. Our approach provides a turnkey and portable solution for lensless polarimetric analysis on a chip, with promising applications in disease diagnosis, crystal screening, and label-free chemical imaging, particularly in resource-constrained environments.

Ultrasensitive tunable terahertz lithium niobate metasurface sensing based on bound states in the continuum

Xinyao Yu, Fanghao Li, Tingting Lang, Jianyuan Qin, and Xiao Ma

DOI: 10.1364/PRJ.501124 Received 21 Jul 2023; Accepted 06 Oct 2023; Posted 06 Oct 2023  View: PDF

Abstract: Lithium niobate's substantial nonlinear optical and electro-optic coefficients have recently thrust it into the limelight. This study presents a thorough review of bound states in the continuum (BICs) in lithium niobate metasurfaces, also suggesting their potential for sensing applications. We propose an all-dielectric tunable metasurface, which offers high Q-factor resonances in the terahertz range, triggered by symmetry-protected BICs. With exceptional sensitivity to changes in the refractive index of the surrounding medium, the metasurface can reach a sensitivity as high as 947 GHz/RIU. This paves the way for ultrasensitive tunable terahertz sensors, offering an exciting path for further research.

Flexible, Self-Powered and Polarization-Sensitive Photodetector Based on Perovskite Lateral Heterojunction microwire Arrays

Shun-Xin Li, Jia-Cheng Feng, Yang An, and Hong Xia

DOI: 10.1364/PRJ.496838 Received 31 May 2023; Accepted 05 Oct 2023; Posted 06 Oct 2023  View: PDF

Abstract: The fabrication of different perovskite materials with superior properties into lateral heterostructures can greatly improve device performance and polarization sensitivity. However, the sensitivity of perovskites to solvents and environmental factors makes the fabrication of lateral heterojunctions difficult. Here, we realize high-quality perovskite microwire crystal heterojunction arrays using regioselective ion exchange. Photodetectors with Responsivity and Detectivity up to 748 AW¯¹ and 8.2×10¹² Jones are fabricated. The photodetector exhibits Responsivity as high as 13.5 AW¯¹ at 0 V bias. In addition, the device exhibits ultra-high polarization sensitivity with a dichroic ratio of 5.6. 81% of its performance was maintained after 144 d of exposure to air.

Long distance all-optical logic operations through a single multimode fiber empowered by wavefront shaping

Zhipeng Yu, Tianting Zhong, huanhuan Li, Haoran Li, Chi Man Woo, shengfu cheng, Shuming Jiao, Honglin Liu, Chao Lu, and Puxiang Lai

DOI: 10.1364/PRJ.499523 Received 05 Jul 2023; Accepted 20 Sep 2023; Posted 22 Sep 2023  View: PDF

Abstract: Multimode fibers (MMFs) are a promising solution for high-throughput signal transmission in the time domain. However, crosstalk among different optical modes within the MMF scrambles input information and creates seemingly random speckle patterns at the output. To characterize this process, a transmission matrix (TM) can be used to relate input and output fields. Recent innovations use TMs to manipulate the output field by shaping the input wavefront for exciting advances in deep-brain imaging, neuron stimulation, quantum networks, and analog operators. However, these approaches consider input/output segments as independent, limiting their use for separate signal processing, such as logic operations. Our proposed method which makes input/output segments as interdependent adjusts the phase of corresponding output fields using phase bias maps superimposed on input segments. Coherent superposition enables signal logic operations through a 15-meter-long MMF. In experiments, a single optical logic gate containing three basic logic functions and cascading multiple logic gates to handle binary operands is demonstrated. Bitwise operations are performed for multi-bit logic operations, and multiple optical logic gates are reconstructed simultaneously in a single logic gate with polarization multiplexing. The proposed method may open new avenues for long-range logic signal processing and transmission via multimode fibers.

High speed silicon photonic electro-optic Kerr modulation

Jonathan peltier, Weiwei Zhang, Leopold Virot, Christian Lafforgue, Lucas Deniel, Delphine Marris-Morini, GUY AUBIN, Farah Amar, Denh Tran, Xingzhao Yan, Callum Littlejohns, Carlos Alonso Ramos, David Thomson, Graham Reed, and Laurent Vivien

DOI: 10.1364/PRJ.488867 Received 28 Feb 2023; Accepted 07 Aug 2023; Posted 08 Aug 2023  View: PDF

Abstract: Silicon-based electro-optic modulators contribute to ease the integration of high-speed and low-power consumption circuits for classical optical communications and data computations.Beyond the plasma dispersion modulation, an alternative solution in silicon is to exploit the DC Kerr effect, which generates an equivalent linear electro-optical effect enabled by applying a large d.c. electric field.Although some theoretical and experimental studies have shown its existence in silicon, limited contribution relative to plasma dispersion have been achieved in high speed modulation so far.This paper presents high-speed optical modulation based on the DC Kerr effect in silicon PIN waveguide.The contributions of both plasma dispersion and Kerr effects have been analyzed in diferent waveguide configurations and we demonstrated that the Kerr induced modulation is dominant when a high external DC electric field is applied in PIN waveguide.High-speed optical modulation response is analyzed and eye diagrams up to 80 Gbits/s in NRZ format are obtained under a d.c. voltage of 30 V.This work paves the way to exploit Kerr effect to generate high speed Pockels-like optical modulation.