Er-Doped Tapered Fiber Amplifier for High Peak Power Sub-ns Pulse Amplification

Maksim M Khudyakov,Mikhail E Likhachev,Mikhail M Bubnov,Konstantin K Bobkov,Svetlana S Aleshkina,Andrei E Levchenko,Aleksei N Gur’Yanov,Leonid V Kotov,Mikhail V Yashkov,Vladimir V Velmiskin

doi:10.3390/photonics8120523

Abstract

A tapered Er-doped fiber amplifier for high peak power pulses amplification has been developed and tested. The core diameter changed from 15.8 µm (mode field diameter (MFD) 14.5 µm) to 93 µm (MFD 40 µm) along 3.7 m maintaining single-mode performance at 1555 nm (according to the S2-method, the part of the power of high-order modes does not exceed 1.5%). The amplification of 0.9 ns pulses with spectral width below 0.04 nm up to a peak power above 200 kW (limited by self-phase modulation) with a slope pump-to-signal conversion efficiency of 15.6% was demonstrated.

Highlights

Erbium-doped fiber (EDF) lasers and amplifiers emitting at the spectral range near 1.55 μm are relatively eye-safe [1]
The shortening of the fiber length is mainly limited by the upconversion of Er3+ ions due to clustering at high concentrations, which leads to a decrease in the pump-to-signal conversion efficiency (PCE) and limits pump absorption
The goal of this work was an optimization of the Tapered EDFs (T-EDFs) parameters to increase the PCE and maintain a high threshold of nonlinear effects at the same time

Summary

Introduction

Erbium-doped fiber (EDF) lasers and amplifiers emitting at the spectral range near 1.55 μm are relatively eye-safe [1] They are widely used in a variety of applications requiring light transmission through the atmosphere, such as wind doppler LIDAR (Light Detection and Ranging) [2,3], atmospheric gas concentration detection from space [4,5], and atmospheric communication. The average power is usually increased by utilizing multimode high power laser diode modules for cladding-pumping double-clad (DC) active fibers In this case, a higher core diameter is beneficial because of the direct correlation between pump absorption and core/cladding ratio. The main way to solve all three issues is to find a way to increase core size while maintaining single-mode operation

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Conclusion