[20p-P3-1~10] 3.6 Ultrashort-pulse and high-intensity lasers

▲ [20p-P3-10] 1.2MW-peak-power sub-picosecond optical pulse source based on a gain-switched laser diode

〇YICHENG FANG^1,2, Tomohiro Chaki^1,2, Hirohito Yamada^1,2, Hiroyuki Yokoyama^1,2 (1.NICHe, Tohoku Univ., 2.Grad.Sch. of Eng., Tohoku Univ.)

Keywords:gain-switched laser diode,self phase modulation,noise reduction

Development of a compact high-peak-power ultrashort optical pulse source is in demand toward wide applications in multi-photon fluorescent microscopy and high-precision material processing. We have generated over 10kW-peak-power picosecond pulses from a light source composed of a gain-switched laser diode (GSLD) and multistage optical fiber amplifiers (OFAs) for two-photon microscopy applications. In a simple mind, we expect to increase further the optical pulse peak-power by reducing the GSLD’s repetition rate under saturation amplification condition of the main OFA. However, due to the low optical average power obtaining from a GSLD at low repetition rate, the amplified spontaneous emission (ASE) noise takes place a large ratio in the optical power after a chain of OFAs, and this reduces the optical pulse peak power significantly. We report that the ASE noise can be reduced by employing self-phase-modulation (SPM) in a passive fiber. In contrast, we demonstrate that a simplified noise reduction scheme is also accomplished by employing SPM in an OFA. Combining with nonlinear pulse compression after the main OFA, our present method has enabled to increase the optical-pulse peak power to over 1 MW.