Abstract

Orbital angular momentum (OAM) beams, featuring with unique spatial field distributions, have been extensively investigated and applied into a wide range of fields. In most applications, OAM beams covering a certain frequency band are usually required, and supercontinuum (SC) generation is a feasible method to provide broadband OAM source. As a short pulse is incident into a specially designed optical fiber with flat dispersion over broad bandwidth, a broadband SC could be generated along propagation due to the nonlinear spectral broadening. In this work, we propose a dual concentric-ring-core fiber design to achieve near-zero and flat dispersion profile over 3007-nm wavelength range with four zero-dispersion wavelengths for the OAM mode. The precise position of the zero-dispersion wavelengths can be tailored by varying the structural variables and the germanium-doped concentration of the silica-based fiber. The performance of the spectral broadening in terms of flatness and bandwidth is investigated under different input pulse and propagation conditions. Simulation results depict that the OAM_3,1 mode supercontinuum spectrum can achieve beyond three-octave spanning from 445 to 3942 nm at −40 dB level by pumping a 50-fs 600-kW Gaussian pulse at the central wavelength of 1900 nm into a 2-mm designed fiber. By further optimizing the proposed fiber structure for the OAM_1,1 mode with <60 ps/(nm·km) dispersion variation over a 3210-nm bandwidth, the generated supercontinuum can cover nearly three octaves.

Silicon waveguide with four zero-dispersion wavelengths and its application in on-chip octave-spanning supercontinuum generation

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Single-mode suspended large-core chalcohalide fiber with a low zero-dispersion wavelength for supercontinuum generation

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Experimental investigation on supercontinuum generation by single, dual, and triple wavelength pumping in a silica photonic crystal fiber

Weiqing Gao, Qiang Xu, Xue Li, Wei Zhang, Jigang Hu, Yuan Li, Xiangdong Chen, Zijun Yuan, Meisong Liao, Tonglei Cheng, Xiaojie Xue, Takenobu Suzuki, and Yasutake Ohishi
Appl. Opt. 55(33) 9514-9520 (2016)

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Opt. Express 15(18) 11553-11563 (2007)