- 标题
- 摘要
- 关键词
- 实验方案
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Large-Dynamic Frequency Response Measurement for Broadband Electro-Optic Phase Modulators
摘要： A novel method for characterizing the frequency responses of broadband electro-optic phase modulators (PMs) by employing stimulated Brillouin scattering (SBS) is proposed and experimentally demonstrated. In the proposed method, the SBS amplifies the +1st-order sideband and attenuates the -1st-order sideband of the phase-modulated signal from a PM under test. Thereby, the phase-modulated signal is converted into an optical single-sideband (OSSB) modulation signal. After square-law photodetection, the overall frequency responses are obtained. Removing the frequency responses of the SBS gain and the photodetector (PD) from the overall responses, the responses of the PM are thus achieved. Benefitting from the amplification of the SBS, the proposed method possesses a large dynamic range. Sub-Hz resolution and broadband measurement range are also achievable. A commercial broadband PM is experimentally characterized from 10 MHz to 50 GHz with a resolution of 5 MHz. According to the amplification of the SBS, the dynamic range is enhanced by 17.74 dB. The measurement result is verified by the conventional method utilizing optical spectrum analysis.
关键词： stimulated Brillouin scattering,Electrooptic modulation,Phase modulation,microwave photonics,optical variables measurement
更新于2025-11-28 14:24:03
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Enhanced optical Kerr nonlinearity of graphene/Si hybrid waveguide
摘要： In this work, we experimentally study the optical Kerr nonlinearities of graphene/Si hybrid waveguides with enhanced self-phase modulation. In the case of CMOS compatible materials for nonlinear optical signal processing, Si and silicon nitride waveguides have been extensively investigated over the past decade. However, Si waveguides exhibit strong two-photon absorption (TPA) at telecommunication wavelengths, which leads to a signi?cant reduction of the nonlinear ?gure-of-merit (FOM). In contrast, a silicon nitride based material system usually suppresses the TPA but simultaneously leads to the reduction of Kerr nonlinearity by one order of magnitude. Here, we introduce a graphene/Si hybrid waveguide, which maintains the optical properties and CMOS compatibility of Si waveguides, while enhancing the Kerr nonlinearity, by transferring over to the top of the waveguides. The graphene/Si waveguides are measured to have an enhanced nonlinear parameter of 510 W(cid:2)1 m(cid:2)1, compared with that of the Si waveguide of 150 W(cid:2)1 m(cid:2)1. An enhanced nonlinear FOM of 2.48 6 0.25 has been achieved, which is four times larger than that of the Si waveguide of 0.6 6 0.1. This work reveals the potential application of graphene/Si hybrid waveguides with high Kerr nonlinearity and FOM for nonlinear all-optical signal processing.
关键词： nonlinear all-optical signal processing,graphene/Si hybrid waveguide,optical Kerr nonlinearity,CMOS compatible,self-phase modulation
更新于2025-11-28 14:23:57
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Vacuum-enhanced optical nonlinearities with disordered molecular photoswitches
摘要： It is well known that nonlinear optical signals such as cross-phase modulation can be coherently enhanced in multilevel atomic gases under conditions of electromagnetically induced transparency, but analogous results in solids are challenging to obtain due to natural energetic disorder. We propose a solid-state cavity QED scheme to enable cross-phase modulation between two arbitrarily weak classical fields in the optical domain, using a highly disordered intracavity medium composed of organic molecular photoswitches. Even in the presence of strong energetic and orientational disorder, the unique spectral properties of organic photoswitches can be used to enhance the desired nonlinearity under conditions of vacuum-induced transparency, enabling cross-phase modulation signals that surpass the detection limit imposed by absorption losses. Possible applications of the scheme include integrated all-optical switching with low photon numbers.
关键词： organic photoswitches,cavity QED,vacuum-induced transparency,cross-phase modulation,disorder
更新于2025-09-23 15:23:52
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Analogue Wireless Beamforming Exploiting the Fiber-Nonlinearity of Radio Over Fiber Based C-RANs
摘要： As a key technique of supporting the fixed backbone network, radio over fiber (RoF) systems transmit the radio frequency signals over optical fiber in order to take advantage of their large available bandwidth. In this context, optical fiber aided phased antenna array (PAA) based beamforming techniques have attracted substantial research interest with the goal of improving the cell-edge coverage of cellular base stations. In this paper, we conceive a novel optical fiber aided beamforming technique based on the fiber's nonlinearity to be applied in cloud radio access network (C-RAN). In our proposed technique, the PAA elements are fed by the phase-shifted signals introduced by our highly nonlinear fiber (HNLF) aided phase-shifting solution, which results in an angular beamsteering range of around 90°. This can be exploited by sectorization in cellular networks to reduce the cochannel interference imposed. Furthermore, we exploit the proposed RoF-aided phase shifting technique in C-RAN, where our proposed system takes advantage of the centralized signal processing capability of the RoF system to conceive an all-optical processing based tunable beamforming system. While our flexible HNLF-aided phase-shifting process is confined to the central office of the C-RAN, the end users in the C-RAN cellular networks are capable of flexibly choosing the serving remote radio heads (RRHs) and employing diverse wireless transmission techniques. Through integrating our HNLF-aided phase-shifting design into the proposed C-RAN, we impose as little as 0.1 dB signal-to-noise Ratio (SNR) degradation compared to its traditional electronic counterpart, which requires extra phase-shifters.
关键词： phase-shifter,self-phase modulation,phased array antenna beamforming,C-RAN,cross-phase modulation,highly nonlinear fiber,Optical fiber,optical nonlinearity
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET) - Chennai (2018.3.22-2018.3.24)] 2018 International Conference on Wireless Communications, Signal Processing and Networking (WiSPNET) - An Efficient Photonic-based Millimeter Wavelength Switching Techniques Towards 5G
摘要： Millimeter Waves (MMWs) operating at 30–300 GHz band, is very encouraging to the next-generation 5G wireless communication systems, supporting data rates of multiple Gbps per user. By using the Four Wave Mixing (FWM), Self-Phase Modulation (SPM) and Cross Phase Modulation (XPM) effects in the Semiconductor Optical Amplifier (SOA) and Erbium Doped Fiber Amplifier (EDFA), the photonic millimeter switching is realized. These effects can reduce the switching crosstalk since the Optical Single Sideband (OSSB) signal occupies the least optical bandwidth. The best operating conditions improve the Sideband Suppression Ratio (SSR) and at the same time reduce the intensity of unintended sideband signal. This leads to a dispersion-free transmission in the optical fiber and improves the data rate as required in 5G communication. In this paper, the wavelength switching of a 9 Gbps QPSK signal carried on the 30 GHz over a spacing of 1.6 nm as a function of probe wavelength of 1548.515 nm and pump wavelength of 1550.115 nm is achieved.
关键词： Millimeter Waves,Four Wave Mixing,Self Phase Modulation,Cross Phase Modulation,Erbium Doped Fiber Amplifier
更新于2025-09-23 15:22:29
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Fast Optical Phased Array Calibration Technique for Random Phase Modulation LiDAR
摘要： Optical phased array (OPA) imaging technique, which uses electro-optic modulation to achieve beam steering rather than mechanical scanning, is a raster scanning imaging method with great potential due to its non-inertia and high-speed. However, fabrication imperfection of an OPA causes pre-designed phase modulations not yielding desired steering angles, and a time-consuming calibration is usually required before practical use. Alternatively, it is possible to obtain images with a random phase modulation OPA. In this work, we propose a fast calibration for the random phase modulation OPA LiDAR. Experimental results demonstrate that, to obtain images of the same quality, the proposed calibration is 3 times faster than the calibration used in raster scanning scheme. In the meantime, the proposed calibration simultaneously retrieves the point spread function of the imaging system during the process, which can be used to remove the image blurring caused by the sidelobes and further improve the image quality.
关键词： calibration,Optical phased array,point spread function,random phase modulation
更新于2025-09-23 15:22:29
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[IEEE 2018 20th International Conference on Transparent Optical Networks (ICTON) - Bucharest (2018.7.1-2018.7.5)] 2018 20th International Conference on Transparent Optical Networks (ICTON) - Offsetting Self-Phase Modulation in Optical Fibre by Sinusoidally Time-Varying Phase
摘要： We report on our recent experimental and theoretical results on the use of a sinusoidally time-varying phase to suppress undesirable self-phase modulation of optical pulses propagating in fibre-optic systems.
关键词： phase modulation,nonlinear fibre optics
更新于2025-09-23 15:22:29
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Experimental Demonstration of Subband Index Techniques for m-CAP in Short Range SI-POF Links
摘要： In this letter, novel spectrally-efficient subband index (SI) techniques have been developed for multiband carrierless amplitude and phase modulation (m-CAP). The subband index techniques transmit additional information bit on the index of the conventional m-CAP subbands. Experimental demonstrations are performed in a short range optical data link using step-index plastic optical fibre (SI-POF). The demonstrations show that the proposed techniques enable flexibility in design and significantly improve the power/spectral efficiency of the conventional m-CAP.
关键词： step-index plastic optical fibre (SI-POF),multiband carrierless amplitude phase modulation (m-CAP),index modulation,Optical communication
更新于2025-09-23 15:21:21
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Highly longitudinally polarized coherent anti-Stokes Raman scattering microscopy with improved spatial resolution
摘要： We proposed a method to enhance the longitudinally polarized component and improve the spatial resolution of radially polarized coherent anti-Stokes Raman scattering (CARS) microscopy by phase modulation. A specially designed phase pattern is applied onto the pump beam to suppress the radially polarized ?eld component at the focal region. With this modulation, the calculated intensity ratio between the longitudinally and radially polarized CARS ?eld is increased from 2.57 to 14.7, and the simulation of CARS imaging on a 120 nm polystyrene bead shows more than 3-fold spatial resolution improvement for both forward and backward detection. It is expected that this method could also be applied to other nonlinear optical imaging modalities for enhancing the longitudinally polarized component.
关键词： spatial resolution,microscopy,phase modulation,longitudinally polarized,coherent anti-Stokes Raman scattering
更新于2025-09-23 15:21:21
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Mathematical Operations of Transmissive Near Fields Controlled by Metasurface with Phase and Amplitude Modulations
摘要： Metasurfaces show great potential due to their powerful ability to manipulate electromagnetic waves as desired, which has been widely investigated in the microwave, terahertz, infrared, and visible regimes. Here, it is proposed to control near-field distributions through use of a metasurface with both amplitude and phase modulations. A C-shaped particle is designed to provide stable and continuous amplitude and phase profiles independently of transmitted waves by varying its opening and orientation angles. Benefiting from both amplitude and phase modulations on the metasurface, differentiation and integration on electric-field distributions can be achieved by changing the arrangements of complex coefficients on the metasurface. Besides, the differential operation can be utilized to show the edges of predesigned electric-field distributions. It is believed that the proposed method will accelerate the pace of metasurfaces towards many applications by engineering and operating the near-field distributions.
关键词： metasurfaces,complex amplitudes,amplitude modulation,phase modulation,integral operations,differential operations
更新于2025-09-23 15:21:01