All-fiber short-wavelength tunable mode-locked fiber laser using normal dispersion thulium-doped fiber

• Main Authors: Chen, Shaoxiang, Chen, Yuhao, Liu, Kun, Sidharthan, Raghuraman, Li, Huizi, Chang, Chen Jian, Wang, Qi Jie, Tang, Dingyuan, Yoo, Seongwoo
• Other Authors: School of Electrical and Electronic Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Electrical and electronic engineering; Fiber Lasers; Normal Dispersion
• Online Access: https://hdl.handle.net/10356/141563
• Institution: Nanyang Technological University

We report an all-fiber high pulse energy ultrafast laser and amplifier operating at the short wavelength side of the thulium (Tm) emission band. An in-house W-type normal dispersion Tm-doped fiber (NDTDF) exhibits a bending-induced distributed short-pass filtering effect that efficiently suppresses the otherwise dominant long wavelength emission. By changing the bending diameter of the fiber, we demonstrated a tunable mode-locked Tm-doped fiber laser with a very wide tunable range of 152 nm spanning from 1740 nm to 1892 nm. Pulses at a central wavelength of 1755 nm were able to be amplified in an all-fiber configuration using the W-type NDTDF, without the use of any artificial short-pass filter or pulse stretcher. The all-fiber amplifier delivers 2.76 ps pulses with an energy of ∼32.7 nJ without pulse break-up, due to the normal dispersion nature of the gain fiber, which marks so far, the highest energy amongst fiber lasers in the 1700 nm-1800 nm region.