High output mode-locked laser empowered by defect regulation in 2D Bi2O2Se saturable absorber

Junting Liu; Fang Yang; Junpeng Lu; Shuai Ye; Haowen Guo; Hongkun Nie; Jialin Zhang; Jingliang He; Baitao Zhang; Zhenhua Ni

doi:10.1038/s41467-022-31606-8

High output mode-locked laser empowered by defect regulation in 2D Bi₂O₂Se saturable absorber

Nat Commun. 2022 Jul 5;13(1):3855. doi: 10.1038/s41467-022-31606-8.

Authors

Junting Liu^#¹, Fang Yang^#², Junpeng Lu³, Shuai Ye¹, Haowen Guo¹, Hongkun Nie¹, Jialin Zhang², Jingliang He¹, Baitao Zhang⁴, Zhenhua Ni⁵

Affiliations

¹ State Key Laboratory of Crystal Materials, Institute of Novel Semiconductors, Shandong University, 250100, Jinan, Shandong, China.
² School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing, 211189, China.
³ School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing, 211189, China. phyljp@seu.edu.cn.
⁴ State Key Laboratory of Crystal Materials, Institute of Novel Semiconductors, Shandong University, 250100, Jinan, Shandong, China. btzhang@sdu.edu.cn.
⁵ School of Physics and Key Laboratory of MEMS of the Ministry of Education, Southeast University, Nanjing, 211189, China. zhni@seu.edu.cn.

^# Contributed equally.

Abstract

Atomically thin Bi₂O₂Se has emerged as a novel two-dimensional (2D) material with an ultrabroadband nonlinear optical response, high carrier mobility and excellent air stability, showing great potential for the realization of optical modulators. Here, we demonstrate a femtosecond solid-state laser at 1.0 µm with Bi₂O₂Se nanoplates as a saturable absorber (SA). Upon further defect regulation in 2D Bi₂O₂Se, the average power of the mode-locked laser is improved from 421 mW to 665 mW, while the pulse width is decreased from 587 fs to 266 fs. Moderate Ar⁺ plasma treatments are employed to precisely regulate the O and Se defect states in Bi₂O₂Se nanoplates. Nondegenerate pump-probe measurements show that defect engineering effectively accelerates the trapping rate and defect-assisted Auger recombination rate of photocarriers. The saturation intensity is improved from 3.6 ± 0.2 to 12.8 ± 0.6 MW cm^-2 after the optimized defect regulation. The enhanced saturable absorption and ultrafast carrier lifetime endow the high-performance mode-locked laser with both large output power and short pulse duration.