Wenchao Qiao

Diode-pumped continuous wave tunable and graphene Q-switched Tm:LSO lasers

We have investigated the lasing characteristics of Tm:LSO crystal in three operation regimes: continuous wave (CW), wavelength tunable and passive Q-switching based on graphene. In CW regime, a maximum output power of 0.65 W at 2054.9 nm with a slope efficiency of 21% was achieved. With a quartz plate, a broad wavelength tunable range of 145 nm was obtained, corresponding to a FWHM of 100 nm. By using a graphene saturable absorber mirror, the passively Q-switched Tm:LSO laser produced pulses with duration of 7.8 μs at 2030.8 nm under a repetition rate of 7.6 kHz, corresponding to pulse energy of 14.0 μJ.

A diode-pumped passively Q-switched Tm,Ho:YAP laser with a single-walled carbon nanotube

In this letter we present diode-pumped continuous wave (CW) and passively Q-switched a-cut and b-cut Tm,Ho:YAP lasers with a single-walled carbon nanotube saturable absorber (SWCNT-SA). In the CW regime, a maximum output power of 1.61 W at 2118.3 nm corresponding to a slope efficiency of 33.7% and a maximum output power of 1.23 W with a slope efficiency of 28.7% at 2129.6 nm were achieved from the a- and b-cut Tm,Ho:YAP lasers, respectively. With a SWCNT employed as the saturable absorber, passively Q-switched a- and b-cut Tm,Ho:YAP lasers were both realized. The a-cut Tm,Ho:YAP laser generated a 245 ns pulse at 2128.3 nm with a repetition rate of 400 kHz, while the b-cut Tm,Ho:YAP laser produced a 135 ns pulse at 2130 nm with a repetition rate of 245 kHz.

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.

Diode-pumped continuous wave and passively Q-switched Tm, Mg: LiTaO3 lasers

We have demonstrated the continuous wave and passively Q-switched Tm, Mg: LiTaO3 lasers for the first time. In continuous wave (CW) regime, a maximum CW output power of 1.03 W at 1952 nm was obtained, giving a slope efficiency of 9.5% and a beam quality M2 = 2.2. In passive Q-switching regime, a single walled carbon nanotube (SWCNT) was employed as saturable absorber (SA). The Tm,Mg:LiTaO3 laser has yielded a pulse of 560 ns under repetition rate of 34.2 kHz at 1926 nm, corresponding to a single pulse energy of 10.1 μJ. The results indicate a promising potential of nonlinear crystals in the applications for laser host materials.

Pulse compression and threshold decrease in high- repetition-rate doubly Q-switched intracavity optical parametric oscillator

By using RbTiOPO4 (RTP) crystals as an electro-optic (EO) modulator and Cr4+:YAG saturable absorber as a passive Q switch, a high repetition rate doubly Q-switched intracavity optical parametric oscillator (IOPO) is realized. In comparison to an EO Q-switched IOPO, the lower threshold energy, the higher output energy, the narrower pulse width, and the higher conversion efficiency from the doubly Q-switched IOPO can be obtained. By considering the gradual loss from the delayed switched time of the EO switch, the coupled rate equations of doubly Q-switched IOPO under the assumption of the uniform distributions of the intracavity photon densities are given, and the numerical solution of the equations fits the experimental data well.

Efficient CW Dual-Wavelength and Passively

Efficient diode-pumped Tm:LuAG lasers operating in continuous wave, dual-wavelength,and passive Q-switching regimes have been demonstrated. A maximum output power of 4.42 W with a beam quality of M2 ≤1.45 at 2021.2 nm was obtained, corresponding to a slope efficiency of 49.5%. Using a birefringent quartz plate, the Tm:LuAG laser emitted the highest output power of 2.3 W at dual-wavelength of 2022 and 2030 nm. With a SWCNT-SA employed as saturable absorber, passively Q-switched Tm:LuAG laser was realized, which generated the shortest pulses of 405 ns at 2021.6 nm and a maximum single pulse energy of 40.6 μJ at 2019.7 nm.

Q

A diode-pumped passively Q-switched mode-locked (QML) intracavity frequency-doubled Nd:GdVO4/KTP green laser with a semiconductor saturable absorber is presented. Nearly 100% modulation depth for the mode-locked green pulses can be achieved at any pump power over 1.92 W. The width of the mode-locked green pulse was estimated to be about 150 ps. The mode-locked pulse interval within the Q-switched envelope of 320 ns and the repetition rate of 97.5 kHz were obtained, at an incident pump power of 4.4 W. The repetition rate of the mode-locked green pulses inside the Q-switched envelope was 140 MHz.

-Switched Tm:LuAG Lasers

A watt-level output passively mode-locked Tm:LuAG bulk laser with an InGaAs semiconductor saturable absorber mirror (SESAM) is demonstrated for the first time. A maximum average output power of 1.21 W at 2022.9 nm has been achieved with a pulse duration of 38 ps and a repetition rate of 129.2 MHz. The results indicate the potential of Tm:LuAG crystals as candidate for realizing high power ultrafast lasers at 2 μm.

Analysis of a laser-diode end-pumped intracavity frequency-doubled passively Q-switched and mode-locked Nd:GdVO4/KTP laser with a semiconductor saturable absorber

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.