Spatial Beam Self-Cleaning in Bi-Tapered Multimode Fibers

Xiao-Jun Lin,Xiang-Yue Li,Yu-Xin Gao,Ai-Ping Luo,Jia-Wen Wu,Jin-Gan Long,Wen-Cheng Xu,Zhi-Chao Luo,Wei-Yi Hong,Hu Cui

doi:10.3390/photonics8110479

Xiao-Jun Lin, Xiang-Yue Li + Show 8 more

Open Access

https://doi.org/10.3390/photonics8110479

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Journal: Photonics	Publication Date: Oct 27, 2021
Citations: 2	License type: CC BY 4.0

Affiliation: South China Normal University, Jinhua Polytechnic

Abstract

We report the spatial beam self-cleaning in bi-tapered conventional multimode fibers (MMFs) with different tapered lengths. Through the introduction of the bi-tapered structure in MMFs, the input beam with poor beam quality from a high-power fiber laser can be converted to a centered, bell-shaped beam in a short length, due to the strengthened nonlinear modes coupling. It is found that the bi-tapered MMF with longer tapered length at the same waist diameter shows better beam self-cleaning effect and larger spectral broadening. The obtained results offer a new method to improve the beam quality of high-power laser at low cost. Furthermore, it may be interesting for manufacturing bi-tapered MMF-based devices to obtain the quasi-fundamental mode beam in spatiotemporal mode-locked fiber lasers.

Highlights

Since we find that the bi-tapered multimode fibers (MMFs) with waist diameter less than 10 μm could not bear the high-power laser, which always causes damage to the waist section of the bi-tapered
The MMF with a tapered length of 3.6 cm is the first sample for spatial beam selfcleaning experiments
The spatial beam self-cleaning behavior in MMFs have been explained in many articles [21,25,28,30,32,33,39]

Summary

Introduction

Since the birth of optical communication, its capacity has grown exponentially, especially with the development of fiber and relevant devices. Such great progress has been achieved with the support of multiplexing and modulation technologies such as wavelength division multiplexing [1], time division multiplexing [2], polarization division multiplexing [3], quadrature amplitude modulation [4], and so on. Space division multiplexing technique [5] shows a possible solution to improve the capacity of communication system, including core division multiplexing in multicore fibers [6,7] and mode division multiplexing in multimode fibers (MMFs) [8,9]. MMF plays an important role in other applications, such as optical imaging [10], high-power laser [11] and mode-locking devices [12]

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