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