分类： 光学 >> 量子光学 提交时间： 2023-02-19
Lili Gui
Chuanshuo Wang
Fei Ding
Hao Chen
Xiaosheng Xiao
Sergey I. Bozhevolnyi
Xiaoguang Zhang
Kun Xu
摘要： Wavelength-tunable vortex fiber lasers that could generate beams carrying orbital angular momentum (OAM) hold great interest in large-capacity optical communications. The wavelength tunability of conventional vortex fiber lasers is however limited by the range of 35 nm due to narrow bandwidth and/or insertion loss of mode conversion components. Optical metasurfaces apart from being compact planar components can flexibly manipulate light with high efficiency in a broad wavelength range. Here, we propose and demonstrate for the first time, to the best of our knowledge, a metasurface-assisted vortex fiber laser that can directly generate OAM beams with changeable topological charges. Due to the designed broadband gap-surface plasmon metasurface, combined with an intracavity tunable filter, the laser enables OAM beam with center wavelength continuously tunable from 1015 nm to 1075 nm, nearly twice of other vortex fiber lasers ever reported. The metasurface can be designed at will to satisfy requirements for either low pump threshold or high slope efficiency of the laser. Furthermore, the cavity-metasurface configuration can be extended to generate higher-order OAM beams or more complex structured beams in different wavelength regions, which greatly broadens the possibilities for developing low-cost and high-quality structured-beam laser sources.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Breathers are localized structures that undergo a periodic oscillation in their duration and amplitude. Optical microresonators, benefiting from their high quality factor, provide an ideal test bench for studying the breathing phenomena. In the monochromatically pumped microresonator system, intrinsic breathing instabilities are widely observed in the form of temporal dissipative Kerr solitons which only exist in the effectively red detuned regime. Here, we proposed a novel bichromatic pumping scheme to create compulsive breathing microcombs via respectively distributing two pump lasers at the effectively blue and red detuned side of a single resonance. We experimentally discover the artificial cnoidal wave breathers and molecular crystal-like breathers in a chip-based silicon nitride microresonator, and theoretically describe their intriguing temporal dynamics based on the bichromatic pumping Lugiato-Lefever equation. In particular, the corresponding breathing microcombs exhibit diverse comb line spacing ranging from 2 to 17 times of the free spectral range of the resonator. Our discovery not only provides a simple and robust method to produce microcombs with reconfigurable comb line spacing, but also reveals a new type of breathing waves in driven dissipative nonlinear systems.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Xingyuan Xu
Weiwei Han
Mengxi Tan
Yang Sun
Yang Li
Jiayang Wu
Roberto Morandotti
Arnan Mitchell
Kun Xu
David J. Moss
摘要： Optical neural networks (ONNs), or optical neuromorphic hardware accelerators, have the potential to dramatically enhance the computing power and energy efficiency of mainstream electronic processors, due to their ultralarge bandwidths of up to 10s of terahertz together with their analog architecture that avoids the need for reading and writing data back and forth. Different multiplexing techniques have been employed to demonstrate ONNs, amongst which wavelength division multiplexing (WDM) techniques make sufficient use of the unique advantages of optics in terms of broad bandwidths. Here, we review recent advances in WDM based ONNs, focusing on methods that use integrated microcombs to implement ONNs. We present results for human image processing using an optical convolution accelerator operating at 11 Tera operations per second. The open challenges and limitations of ONNs that need to be addressed for future applications are also discussed.
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