High-power passively Q-switched 2  μm all-solid-state laser based on a Bi_2Te_3 saturable absorber

Abstract

By using the ultrasound-assisted liquid phase exfoliation method, Bi 2 Te 3 nanosheets are synthesized and deposited onto a quartz plate to form a kind of saturable absorber (SA), in which nonlinear absorption properties around 2 μm are analyzed with a home-made mode-locked laser. With the as-prepared Bi 2 Te 3 SA employed, a stable passively Q-switched all-solid-state 2 μm laser is successfully realized. Q-switched pulses with a maximum average output power of 2.03 W are generated under an output coupling of 5%, corresponding to the maximum single-pulse energy of 18.4 μJ and peak power of 23 W. The delivered shortest pulse duration and maximum repetition rate are 620 ns and 118 kHz under an output coupling of 2%, respectively. It is the first presentation of such Bi 2 Te 3 SA employed in a solid-state Q-switched crystalline laser at 2 μm, to the best of our knowledge. In comparison with other 2D materials suitable for pulsed 2 μm lasers, the saturable absorption performance of Bi 2 Te 3 SA is proved to be promising in generating high power and high-repetitionrate 2 μm laser pulses.

Recent Progress in 2D Material‐Based Saturable Absorbers for All Solid‐State Pulsed Bulk Lasers

“…With TMD SAs, the shortest pulse width of 220 ns was achieved with MoS 2 in a passively Q‐switched Tm:KLuW laser, while it was 181 ns with a BP SA . In 2017, Yang's group reported the only demonstration of Bi 2 Te 3 ‐SA passively Q‐switched 2.0 µm all solid‐state bulk lasers, which generated a pulse width of 620 ns and an output power of 2.03 W ( Figure b) . In 2017, Tu's group reported a passively Q‐switched Tm:YAP laser based on a Bi 2 Te 3 /G heterostructure, realizing a pulse width of 238 ns and an output power of 2.34 W .…”

Passively Q-switched Tm/Ho composite laser

“…With the development of 2 μm saturable absorbers, such as 1D materials (single wall carbon nanotube and gold nanorod) 14,15 , 2D materials (graphene, topological insulators, and ternary chalcogenides) [16][17][18] , and transition metal ion-doped II-VI crystals (Cr 2+ :ZnSe, Cr 2+ :ZnS) 19,20 , passively Q-switching (PQS) in 2 μm Tm-doped and Ho-doped lasers has become a hot topic, which is characterized by compactness, easy implementation, and cost-saving compared with the actively Q-switching (AQS) manners. Among the above SAs, Cr 2+ :ZnSe/ZnS crystals were demonstrated to be robust for achieving higher pulse energy and better PQS stability 19 , owing to the mature crystal growth process with fewer defects.…”

Graphdiyne as a saturable absorber for 2-µm all-solid-state Q-switched laser

“…In 2004, graphene (G) (sp 2 ) was successfully fabricated and used as SA for Q-switched or mode-locked regimes, thereby facilitating new opportunities for the development of pulsed lasers [9][10][11][12]. Since then, different kinds of twodimensional (2D) materials, such as topological insulators, transition metal dichalcogenides, black phosphorus, and MXenes, have been uninterruptedly discovered and widely used for generating pulsed lasers at spectral wavebands ranging from visible to mid-infrared [13][14][15][16][17][18][19][20][21]. The application of 2D materials based on SA is attributed to their excellent nonlinear optical absorption characteristics, such as ultrafast recovery time, controllable modulation depth and low nonsaturable loss, convenience, and low budget.…”