Ultralow Saturation Intensity Topological Insulator Saturable Absorber for Gigahertz Mode-Locked Solid-State Lasers

Abstract

The successful demonstration of Q-switched and mode-locked fiber-laser operations using a topological insulator (TI) as saturable absorber (SA) has opened an application window besides TI's originally expected features. However, to date, all-solid-state mode-locked lasers base on TISAs are still unavailable and became a desired goal not only due to their application as light sources, but also because of providing a way for deeper investigation of the nature of ultrafast dynamics present in TISAs. In this paper, the realization of a continuous-wave mode-locked all-solid-state laser with a repetition rate of around 1 GHz is reported using a high-quality TI SA mirror (TI-SAM) with ultralow saturation intensity, fabricated by a spin coating-co-reduction approach. An output power of 180 mW and pulse duration of 8 ps are observed. In addition, a 61 dB pulse-train quality from the radio frequency spectrum of mode-locked operation prove the feasibility of the proposed laser. To the best of our knowledge, this is the first experimental demonstration of a mode-locked solid-state laser based on TIs. In addition, this paper shows that the use of TISAs is a promising option for the realization of scaling solid-state mode-locked lasers with higher repetition rates, reaching order of GHz.

Recent Progress of Two-Dimensional Materials for Ultrafast Photonics

“…In 2018, Wang et al demonstrated an all-solid-state mode-locked laser based on a large-area Bi Te SA mirror prepared by the spinning coating-co-reduction approach (SCCA), which had a repetition rate up to 1 GHz, output power up to 180 mW, and SNR of 61 dB [ 230 ]. These results indicates that TIs could be potential SAs in solid-state lasers for the generation of highly stable ultrafast pulses.…”

Dynamic cavity effects in topological insulator Bi2Te3 based passive Q-switched solid state laser

“…However, special care can be taken in the cavity design to maintain sufficient modulation depth. For example, increasing the mode area at the SA become crucial to initiate QS-ML and even CW-ML under a relative low absorbed pump power of 100mW and 500 mW, respectively at a relatively high repetition rate of agigahertz [35].…”

2 μm passively mode-locked thulium-doped fiber lasers with Ta2AlC-deposited tapered and side-polished fibers

“…It was expected that Ta 2 AlC-deposited tapered fiber would have the lowest mode-locking threshold, as it had the lowest saturation intensity compared to the 1.63% of the Ta 2 AlC-deposited SPF and 1.03% of the Ta 2 AlC-deposited arc-shaped fiber. A low saturation intensity would allow the SA to be saturated at a lower pump power to induce the mode-locking operation 79 .…”