Chao Luan

WS 2 as a saturable absorber for Q-switched 2 micron lasers

We prepared WS2 nanosheets by using the thermal decomposition method and demonstrated for the first time its nonlinear saturable absorption property at around 2 μm. With the as-prepared WS2 nanosheets as saturable absorber (SA), a passively Q-switched Tm:LuAG laser was realized successfully, and 660 ns laser pulses with an average output power of 1.08 W and pulse peak power of 26 W at a repetition rate of 63 kHz were obtained for an incident pump power of 7 W. Our experimental results definitely demonstrate that WS2 could be a kind of promising SA for solid-state 2 μm lasers.

High-Peak Power Passively Q-Switched 2-μm Laser With MoS 2 Saturable Absorber

The passive Q-switching characteristics of a diode-pumped Tm,Ho:YAP laser at 2 μm based on a MoS2 saturable absorber (SA) is presented for the first time. Pulses as short as 435 ns under a repetition rate of about 55 kHz were generated at the incident pump power of 8.4 W, corresponding to the pulse peak power up to 11.3 W. This is, to the best of our knowledge, the highest pulse peak power, ever obtained from MoS2 based passively Q-switched 2-μm lasers. The experimental results sufficiently validated the feasibility of MoS2 as SA for solid-state 2-μm lasers.

Passively Q-Switched Laser at 1.3 μm With Few-Layered MoS2 Saturable Absorber

Solid-state passively Q-switched Nd:LuAG laser at 1.3 μm with few layered MoS2 as saturable absorber has been experimentally realized and demonstrated. The shortest pulse width of 188 ns and pulse repetition rate of 73 kHz were obtained. The experimental results verified the broadband saturable absorption characteristics of MoS2 and indicated its ability to generate short pulses.

Diode-pumped mode-locked Tm:LuAG laser at 2 μm based on GaSb-SESAM

Mode-locking of a directly diode-pumped Tm:LuAG laser is demonstrated using GaSb-based semiconductor saturable absorber mirrors (SESAMs). Stable and self-starting mode-locked operation was realized, generating pulses as short as 13.6 ps at 2024 nm with a maximum output power of 98 mW. Two GaInAs-based SESAMs were used for comparison with the operation based upon the use of the GaSb SESAM; in this case, longer pulses with durations of 27 ps and 34 ps were obtained under the same experimental conditions. Our work sets a new record in pulse duration for mode-locked Tm:LuAG lasers and confirms that lattice-matched GaSb-based SESAMs are beneficial for mode-locked solid-state lasers in the 2 μm range.

Growth and lasing performance of a Tm,Y:CaF 2 crystal

A Tm3+ ion and Y3+ ion co-doped CaF2 crystal was grown and characterized, in which spectral and lasing performance was presented for the first time, to the best of our knowledge. Under diode end-pumping, in a continuous-wave regime, maximum output power of 453 mW was delivered under an absorption pump power of 2.5 W, corresponding to an optical-to-optical conversion efficiency of 17.9% and a slope efficiency of 21%. With a birefringent quartz plate, wavelength-tunable operation with a tunable range of more than 190 nm was realized. The results show that Tm,Y:CaF2 is a promising laser crystal operating in a spectral region ranging from 1850 nm to 2050 nm.

High peak power, 28 ns Q-switched Tm:LuAG laser at a 2 μm wavelength by dual-loss-modulation

By employing output couplers (OCs) with different transmissions T and GaAs saturable absorbers (SAs) with different modulation depth ΔR in a passively Q-switched Tm:LuAG laser at 2 μm, the optimal parameters of OCs and SAs for obtaining short pulse width and high peak power were investigated. By inserting an electro-optical modulator (EOM) into the optimized passively Q-switched Tm:LuAG laser (T = 2%/ΔR = 19%), a dual-loss-modulated Q-switched Tm:LuAG laser with an EOM and GaAs was realized. The experimental results show that the dual-loss-modulated Q-switched laser can generate a shorter pulse width and higher peak power than the single-loss-modulated case. At an incident pump power of 8.4 W, the shortest pulse width achieved was 28 ns and the highest peak power reached 74 kW.

Doubly Q-Switched Laser With AOM- and SWCNT-SA-Driven KTP Intracavity OPO

By simultaneously using an acousto-optic modulator (AOM) and a single-walled carbon nanotube saturable absorber, an intracavity optical parametric oscillation (IOPO) in KTiOPO4 pumped by a dual-loss-modulated Q-switched laser has been demonstrated. With an incident pump power of 8.3 W and an AOM modulation rate of 20 kHz, the maximum output power of 375 mW for signal waves was obtained, corresponding to an optical-conversion efficiency of 4.5%. In comparison with IOPO pumped by a singly Q-switched laser with an AOM, the IOPO pumped by doubly Q-switched laser can generate signal light with shorter pulse width and higher peak power as well as better pulse stability.

Diode-pumped mode-locked Tm:LuAG 2 μm laser based on GaSb-SESAM

Ultrafast 2μm lasers are capturing a growing interest for the use as pump and seed sources in optical parametric systems operating in the mid-IR, for IR super-continuum generation, and for time-resolved spectroscopy. However, the demonstration of solid-state ultrashort 2 μm laser based on passive mode-locking lacks behind similar developments with established gain media, at 1 μm for example, partially due to a lack of technological developments of the key components — saturable absorbers (SAs) [1]. In the mid-IR wavelength region, GaSb material exhibits exceptional advantages. The GaSb-based SESAMs comprising GaInSb/GaSb (Quantum-wells) QWs exhibit a fast sub-ps absorption recovery time as a result of the significantly stronger Auger recombination, so a fast relaxation time without the need for ion implantation or low-temperature growth, combined with possibility to vary the number of QWs almost without any strain-related limitation, makes GaSb-based SESAMs attractive for mode-locking at 2 μm.

High-peak-power sub-nanosecond intracavity KTiOPO4 optical parametric oscillator pumped by a dual-loss modulated laser with acousto-optic modulator and single-walled carbon nanotube

A high-peak-power low-repetition-rate sub-nanosecond intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) pumped by a doubly Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser with an acousto-optic modulator (AOM) and a single-walled carbon nanotube saturable absorber (SWCNT-SA) has been demonstrated. A maximum output power of 373 mW at a signal wavelength of 1570 nm was obtained. The smallest pulse width, highest pulse energy, and greatest peak power of mode-locking pulses were estimated to be 119 ps, 124 µJ, and 1.04 MW, respectively, under a maximum incident pump power of 8.3 W and an AOM repetition rate of 2 kHz. This OPO operation paves a simple way to produce eye-safe laser sources at 1570 nm with low repetition rates, small pulse widths, and high peak powers.