Hongwei Chu

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.

Dual-Wavelength Passively Q-Switched Nd,Mg:LiTaO 3 Laser With a Monolayer Graphene as Saturable Absorber

Compact LD pumped, CW, and passively Q-switched Nd,Mg:LiTaO3 lasers with a stable, synchronous dual-wavelength operation near 1082 and 1092 nm were demonstrated for the first time. Under an incident pump power of 7.69 W, a maximum CW output power of 464 mW was obtained, corresponding to a slope efficiency of 7.6%. By using a monolayer graphene as saturable absorber, the steadily Q-switched Nd,Mg:LiTaO3 laser with dual-wavelength oscillation was achieved. The maximum output power of the Q-switched laser was 365 mW with a repetition rate of 133 kHz. The minimum pulse duration was measured to be 176 ns. The corresponding maximum pulse energy and peak power were 2.75 μJ and 15.7 W, respectively.

Simultaneous operations at 1125 nm, 1161 nm, and 1567 nm from a single KTiOPO4 crystal pumped by a passively Q-switched Nd:GGG laser.

A multiwavelength operation generated from an intracavity optical parametric oscillator (OPO) pumped by a passively Q-switched Nd:GGG laser with a Cr(4+):YAG saturable absorber is demonstrated. KTiOPO4 simultaneously worked as nonlinear OPO and Raman crystal. Maximum output powers of 302 mW at 1566.8 nm and 115 mW at 1124.9/1160.7 nm were obtained at a diode power of 10.5 W, corresponding to the optical-to-optical conversion efficiencies of 2.88% and 1.1%, respectively. The measured shortest pulse duration at 1566.8 nm was 1.61 ns, while the obtained minimum pulse duration at 1124.9/1160.7 nm was 2.88 ns.

Intracavity KTP-based OPO pumped by a dual-loss modulated, simultaneously Q-switched and mode-locked Nd:GGG laser

An intracavity KTiOPO(4) (KTP) optical parametric oscillator (OPO) pumped by a simultaneously Q-switched and mode-locked (QML) Nd:Gd(3)Ga(5)O(12) (Nd:GGG) laser with an acousto-optic modulator (AOM) and a Cr(4+):YAG saturable absorber is presented. A minimum mode-locking pulse duration underneath the Q-switched envelope was evaluated to be about 290 ps. A maximum QML output power of 82 mW at the signal wavelength of 1570 nm was achieved, corresponding to a maximum mode-locked pulse energy of about 5.12 μJ. The M(2) values were measured to be about 1.3 and 1.5 for tangential and sagittal directions using knife-edge technique.

Diode-pumped passively Q-switched Nd:GGG laser with a double-walled carbon nanotube saturable absorber

A diode-end-pumped passively Q-switched Nd:GGG laser with a double-walled carbon nanotube (DWCNT) saturable absorber is demonstrated for the first time. A maximum output power of 1.03 W and a minimum pulse duration of 24.3 ns with a highest peak power of 121 W were obtained. The pulse repetition rate varied from 122 to 350 kHz as the pump power increased. The experimental results show that DWCNT is an excellent saturable absorber for passive Q-switched lasers.

Simultaneous dual-wavelength operation around 1.06 μm of a LD-end-pumped, passively Q-switched Nd:GGG laser with GaAs as saturable absorber

By using neodymium-doped gadolinium gallium garnet (Nd:GGG) as the laser medium, a passively Q-switched simultaneous dual-wavelength Nd:GGG laser with a GaAs saturable absorber has been realized. The Nd:GGG laser operates at a stable dual-wavelength peaked at 1060.8 and 1062.7?nm without any wavelength selective elements in the cavity. Stable Q-switched pulses with a shortest duration of 6?ns have been obtained, corresponding to a single pulse energy of 2.1??J and a peak power of 335?W.

KTP OPO with signal wave at 1630 nm intracavity pumped by an efficient σ-polarized Nd,MgO:LiNbO 3 laser

An efficient, 808-nm-laser-diode end-pumped, σ-polarized Nd,MgO:LiNbO3 laser emitting at 1094 nm was demonstrated for the first time. The maximum output power of 1.49 W was obtained at the absorbed diode pump power of 6.48 W, corresponding to an optical-to-optical conversion efficiency of about 23%. The slope efficiency was approximately 25.7%. For applications, an intracavity optical parametric oscillator (IOPO) pumped by an actively Q-switched Nd,MgO:LiNbO3 laser with an acousto-optic modulator (AOM) was realized. An X-cut KTiOPO4 (KTP) worked as the nonlinear crystal for type II noncritical phase matching (NCPM). A maximum output power of the signal wavelength at 1630 nm was about 96 mW with a minimum pulse duration of 1.69 ns at an AOM repetition rate of 5 kHz, giving a peak power of 11.4 kW.

Diode-pumped Nd:Gd3Ga5O12–KTiOPO4 green laser doubly passively Q-switched mode-locked by GaAs and Cr4+:YAG saturable absorbers

By simultaneously employing GaAs and Cr4+:YAG saturable absorbers, a diode-pumped doubly passively Q-switched and mode-locked (DP-QML) Nd:Gd3Ga5O12 (Nd:GGG)/KTiOPO4 (KTP) green laser has been presented. At the maximum incident pump power of 7.69 W, the obtained average output power, the pulse duration of the Q-switched envelope, the mode-locked pulse width and the pulse repetition rate are 62 mW, 16.8 ns, 352 ps, and 15.5 kHz, respectively, corresponding to a pulse energy of 4.2 µJ and a peak power of 0.25 kW. In comparison with singly passively Q-switched and mode-locked (SP-QML) green laser with GaAs or Cr4+:YAG saturable absorbers, the DP-QML green laser can generate shorter pulse width, deeper modulation depth and higher peak power. The coupled equations for diode-pumped doubly passively QML Nd:GGG/KTP green laser are given and the numerical simulations are in good agreement with the experimental results.

Simultaneous Stokes and Anti-Stokes Lines Operation Within a Yb:YAG Laser at 1050 nm

An intracavity cascaded Raman laser with the Stokes and anti-Stokes emissions from a single KTiOPO4 crystal pumped by a passively Q-switched Yb:YAG laser near 1050 nm was demonstrated. A total conversion output power of 666 mW was obtained at a repetition rate of 9.8 kHz with an overall conversion efficiency of ~3%. The shortest pulse duration of the third Stokes radiation near 1148 nm was measured to be 764 ps, giving out a pulse energy of 13 μJ and peak power of 17.1 kW. Meanwhile, pulse duration of 1.54 ns at anti-Stokes line was also obtained with a peak power of 3.5 kW. The effective Raman gain was estimated to be ~2.1 cm/GW.