Semiconductor saturable absorber mirror in the 3–5 µm mid-infrared region

• DOI: 10.1364/ol.444485
• Publication Date: 2022-01-03T17:32:49Z
• Authors: Zhipeng Qin; Xuliang Chai; Guoqiang Xie; Zhicheng Xu; Yi Zhou; Qi Wu; Jie Li; Zhuan Wang; Yuxiang Weng; Ting Hai; Peng Yuan; Jingui Ma; Jianxin Chen; Liejia Qian
• Keywords: 0103 physical sciences; 01 natural sciences

Semiconductor saturable absorber mirrors (SESAMs) have been regarded as a revolutionary technology for ultrafast mode-locked lasers, producing numerous landmark laser breakthroughs. However, the operating wavelength of existing SESAMs is limited to less than 3 µm. In this study, we create a 3–5 µm mid-infrared (MIR) SESAM by engineering an InAs/GaSb type-II superlattice. Bandgap engineering and the strong coupling between potential wells in a superlattice enable a broadband response of saturable absorption in the 3–5 µm spectral range. Using the fabricated SESAM, we realize a SESAM mode-locked Er:ZBLAN fiber laser at 3.5 µm, which delivers MIR ultrashort pulses with high long-term stability. The breakthrough of SESAM fabrication in the MIR will promote the development of MIR ultrafast coherent sources and related application fields.