An approach for frequency division of an optical pulse train (OPT) based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated
An approach for frequency division of an optical pulse train (OPT) based on an optoelectronic oscillator (OEO) is proposed and experimentally demonstrated. When the OPT is injected into the OEO, a microwave signal with a frequency equaling fractional multiples of the repetition rate of the OPT is generated. This signal is then fed back to the OEO, maintaining its oscillation, while simultaneously serving as the control signal of a Mach–Zehnder modulator (MZM) in the OEO. The MZM acts as an optical switch, permitting specific pulses to pass through while blocking others. As a result, the repetition rate of the OPT is manipulated. A proof-of-concept experiment is carried out. Frequency division factors of 2 and 3 are successfully achieved. The phase noises of the OPT before and after the frequency division are investigated. Compared to previously reported systems, no external microwave source and sophisticated synchronization structure are needed.show less
With the rapid development of sensor networks, machine vision faces the problem of storing and computing massive data. The human visual system has a very
With the rapid development of sensor networks, machine vision faces the problem of storing and computing massive data. The human visual system has a very efficient information sense and computation ability, which has enlightening significance for solving the above problems in machine vision. This review aims to comprehensively summarize the latest advances in bio-inspired image sensors that can be used to improve machine-vision processing efficiency. After briefly introducing the research background, the relevant mechanisms of visual information processing in human visual systems are briefly discussed, including layer-by-layer processing, sparse coding, and neural adaptation. Subsequently, the cases and performance of image sensors corresponding to various bio-inspired mechanisms are introduced. Finally, the challenges and perspectives of implementing bio-inspired image sensors for efficient machine vision are discussed.show less
Based on the wavelength transparency of the Butler matrix (BM) beamforming network, we demonstrate a multi-beam optical phased array (MOPA) with an emitti
Based on the wavelength transparency of the Butler matrix (BM) beamforming network, we demonstrate a multi-beam optical phased array (MOPA) with an emitting aperture composed of grating couplers at a 1.55 μm pitch for wavelength-assisted two-dimensional beam-steering. The device is capable of simultaneous multi-beam operation in a field of view (FOV) of 60°
We propose a joint look-up-table (LUT)-based nonlinear predistortion and digital resolution enhancement scheme to achieve high-speed and low-cost optical
We propose a joint look-up-table (LUT)-based nonlinear predistortion and digital resolution enhancement scheme to achieve high-speed and low-cost optical interconnects using low-resolution digital-to-analog converters (DACs). The LUT-based predistortion is employed to mitigate the pattern-dependent effect (PDE) of a semiconductor optical amplifier (SOA), while the digital resolution enhancer (DRE) is utilized to shape the quantization noise, lowering the requirement for the resolution of DAC. We experimentally demonstrate O-band intensity modulation and direct detection (IM/DD) transmission of 124-GBd 4 / 6-level pulse-amplitude modulation ( PAM ) -4 / 6 and 112-GBd PAM-8 signals over a 2-km standard single-mode fiber (SSMF) with 3 / 3.5 / 4-bit DACs. In the case of 40-km SSMF transmission with an SOA-based preamplifier, 124-GBd on-off-keying (OOK)/PAM-3/PAM-4 signals are successfully transmitted with 1.5 / 2 / 3-bit DACs. To the best of our knowledge, we have achieved the highest net data rates of 235.3-Gb / s PAM-4, 289.7-Gb / s PAM-6, and 294.7 Gb / s PAM-8 signals over 2-km SSMF, as well as 117.6-Gb / s OOK, 173.8-Gb / s PAM-3, and -231.8 Gb / s PAM-4 signals over 40-km SSMF, employing low-resolution DACs. The experimental results reveal that the joint LUT-based predistortion and DRE effectively mitigate the PDE and improve the signal-to-quantization noise ratio by shaping the noise. The proposed scheme can provide a powerful solution for low-cost IM/DD optical interconnects beyond 200 Gb / s.show less
Random fiber lasers have attracted extensive attention due to their rich physical properties and wide applications. Here, a novel random fiber laser (RFL) using a cascaded fiber loop mirror (FLM
Random fiber lasers have attracted extensive attention due to their rich physical properties and wide applications. Here, a novel random fiber laser (RFL) using a cascaded fiber loop mirror (FLM) is proposed and presented. A cascaded FLM with ten FLMs is simulated by the transfer matrix method and used to provide the random feedback. Multiple spikes are observed in both the simulated and measured reflection spectra. The RFL operates in a single longitudinal mode near the threshold and a time-varying multi-longitudinal mode at higher pump powers. The RFL exhibits a time-varying radio frequency spectrum. The Levy-Gaussian distribution transition is observed as in many RFLs. The operation mechanism of the lasing longitudinal modes and the impact of complex mode competition and mode hopping on the output characteristics are discussed through experimental and theoretical results. This study unveils a new artificial random feedback structure and paves a new way for the realization of RFLs, which should be a novel platform for multidisciplinary studies in complex systems.show less
High-order Laguerre-Gaussian (LG) petal-like beams have become a topic of significant interest due to their potential application in next generation optical trapping, quantum optics, and materia
High-order Laguerre-Gaussian (LG) petal-like beams have become a topic of significant interest due to their potential application in next generation optical trapping, quantum optics, and materials processing technologies. In this work we demonstrate the generation of high-order LG beams with petal-like spatial profiles and tunable orbital angular momentum (OAM) in the mid-infrared wavelength region. These beams are generated using idler-resonant optical parametric oscillation (OPO) in a KTiOAsO4 (KTA) crystal. By adjusting the length of the resonant cavity, the OAM of the mid-infrared idler field can be tuned and we demonstrate tuning in the range 0 ~ ±10. When using a maximum pump energy of 20.2 mJ, the maximum output energy of high-order modes LG0,±5, LG0,±8 and LG0,±10 were 0.8 mJ, 0.53 mJ and 0.46 mJ respectively. The means by which high-order LG modes with petal-like spatial profiles and tunable OAM were generated from the OPO is theoretically modelled by examining the spatial overlap efficiency of the beam waists of the pump and resonant idler fields within the center of KTA crystal. The methodology presented in this work offers a simple and flexible method to wavelength convert laser emission and generate high-order LG modes.show less
In the field of long-wave infrared (LWIR) thermal imaging, vital for applications such as military surveillance and medical diagnostics, metalenses show immense potential for compact, lightweigh
In the field of long-wave infrared (LWIR) thermal imaging, vital for applications such as military surveillance and medical diagnostics, metalenses show immense potential for compact, lightweight, and low-power optical systems. However, to date, the development of LWIR broadband achromatic metalenses with dynamic tunable focus, which are suitable for both coaxial and off-axis applications, remains a largely unexplored area. Herein, we have developed an extensive database of broadband achromatic all-As2Se3 microstructure units for the LWIR range. Utilizing this database with the Particle Swarm Optimization (PSO) algorithm, we have designed and demonstrated LWIR broadband achromatic metalenses capable of coaxial and off-axis focusing with three dynamic tunable states. This research may have potential applications for the design of compact, high-performance optical devices, including those with extreme depth-of-field and wide-angle imaging capabilities.show less
Lasers from ¹I₆ to ³F₄ transitions were first demonstrated in a Pr³⁺:YLF crystal by inserting a birefringent filter. Output powers up to 2.44 W, 2.10 W, 2.01 W and 2.42 W were obt
Lasers from ¹I₆ to ³F₄ transitions were first demonstrated in a Pr³⁺:YLF crystal by inserting a birefringent filter. Output powers up to 2.44 W, 2.10 W, 2.01 W and 2.42 W were obtained at 691.7 nm, 701.4 nm, 705.0 nm and 708.7 nm. Their slope efficiencies were 19.8%, 16.5%, 15.8% and 19.4%, respectively. The Mx² and My² factors were measured to be 2.29 and 2.03 at 691.7 nm, 2.23 and 1.86 at 701.4 nm, 2.31 and 2.08 at 705.0 nm, and 2.41 and 2.04 at 708.7 nm, with corresponding power fluctuations of less than 5.3%, 5.6%, 5.8%, and 2.9%.show less