High-repetition-rate eye-safe intracavity KTA OPO driven by a diode-end-pumped Q-switched Nd:YVO4 laser

An eye-safe, high-repetition-rate, single-resonant nanosecond intracavity optical parametric oscillator (IOPO), based on a non-critically phase-matched KTA crystal driven by a diode-end-pumped acousto-optically Q-switchedNd:YVO4 laser, was demonstrated for the first time to our knowledge. With an absorbed pump power of 11.3 W, 1.1 W average power and 2.5 ns pulse width at the signal (1534 nm) wavelength for 30-kHz repetition rate are synchronously achieved with the 25 mm long KTA crystal. The corresponding peak power and single pulse energy are estimated to be up to 14.7 kW and 36.7 μJ. The conversion efficiency from diode laser power to OPO signal output power was 9.8% and the corresponding slope efficiency was 15.4%. PACS 42.60.Gd; 42.65.Yj; 42.55.Xi     

Study on optical characteristics of Nd:YVO4/YVO4 composite crystal laser

Thermal effect in crystals is the main obstacle blocking diode-pumped solid state laser to get high and stable output power. Diffusion bonding crystal has been demonstrated to be an effective method to relieve the thermal lensing theoretically based on the numerical heat analysis to the end-pumped anisotropic laser crystal. The temperature distributions in Nd:YVO4/YVO4 composite crystal and conventional crystal were analyzed and compared. The end-pumped Nd:YVO4/YVO4 composite crystal laser was designed and set up with z-cavity. The maximum output powers of 9.87 W at 1064 nm and 6.14 W at 532 nm were obtained at the incident pump power of 16.5 W. The highest optical-optical conversion efficiencies were up to 59.8% at 1064 nm and 37.2% at 532 nm respectively.     

Second-Stokes YVO4/Nd:YVO4/YVO4 self-frequency Raman laser

We demonstrated an efficient second-Stokes Raman laser emission at 1313 nm based on self-frequency stimulated Raman scattering from a diode-end-pumped actively Q-switched YVO(4)/Nd:YVO(4)/YVO(4) laser at 1064 nm for the first time, to the authors' knowledge. A double-end diffusion-bonded Nd:YVO(4) composite crystal was adopted for sufficiently improving the thermal lensing effect in the course of self-frequency stimulated Raman scattering operation. With an incident pump power of 14.6 W and a pulse repetition (PRR) of 40 kHz, a maximum average output power of 2.34 W was obtained, corresponding to an optical-to-optical conversion efficiency of 16%. Pulse width and peak power were 1.2 ns and 49 kW, respectively.     

A compact efficient continuous-wave self-frequency Raman laser with a composite YVO4/Nd:YVO4/YVO4 crystal

We report a low-threshold continuous-wave self-Raman laser with a composite YVO₄/Nd:YVO₄/YVO₄ crystal. The use of the composite crystal can reduce the thermal effects and achieve the low-threshold and high Raman output operation. The Raman threshold is as low as 2.2 W for the 808-nm diode pump. Under the pump of a diode power of 25.5 W, the highest Raman output of 2.8 W is obtained at 1175 nm, corresponding to a slope efficiency of 12% and a diode-to-Stokes optical conversion efficiency of 11%. The power fluctuation is less than 1.1% under the highest Raman output.     

An eye-safe KTiAsO4 intracavity optical parametric oscillator driven by a diode pumped composite Nd:YAG/Cr4+:YAG laser

A mini eye-safe KTiAsO₄ intracavity optical parametric oscillator (IOPO) employing the shared cavity configuration and driven by a diode-end-pumped composite Nd:YAG/Cr⁴⁺:YAG laser is demonstrated in this paper. Under an incident laser diode power of 11 W, a maximum average output power of 424 mW at 1534 nm was obtained. The corresponding signal pulse width and repetition rate were 1.2 ns and 16.7 kHz, respectively. The fluctuation of the average signal output power over long-term operation was found to be ±3.0%. A theoretical model for the compact IOPO was also presented in this paper.     

Comparison of eye-safe KTA OPOs pumped by Nd:YVO4 and Nd:YLF lasers

An eye-safe KTA OPO pumped by a Nd:YLF laser is demonstrated and a comparison with that pumped by a Nd:YVO₄ laser is performed. Although the slope efficiency of the continuous-wave free-running Nd:YLF laser is lower than that of the Nd:YVO₄ laser, the performance of KTA OPOs pumped by the Q-switched Nd:YLF laser is better, especially at lower repetition rates. The slope efficiency of KTA OPO pumped by a Nd:YLF laser is 14.6% at 30 kHz and 11.04% at 10 kHz. The better energy storage ability of Nd:YLF makes it an excellent laser medium in IOPOs.     

High-power diode-pumped nonlinear mirror mode-locked Nd:YVO4 laser with periodically-poled KTP

We demonstrate a high-power nonlinear mirror (NLM) mode-locked Nd:YVO₄ laser with a periodically poled KTP (PPKTP). With a 10-mm-long PPKTP crystal, 5.6 W of average power with 20-ps of pulse duration was generated at 18-W of pump power. Compared with conventional type-II KTP crystal with the same length, the stability against the Q-switched mode-locking (QML) is significantly increased with PPKTP in NLM laser; and the pulse duration was also considerably reduced. Received: 21 July 2000 / Revised version: 30 August 2000 / Published online: 10 January 2001     

High-power diode-pumped picosecond Nd(3+):YVO(4) laser

A diode-pumped Nd(3+):YVO(4) laser passively mode locked by a nonlinear mirror based on second-harmonic generation has been developed. Pumping with a fiber-coupled 10-W diode array, we generated nearly diffraction limited, linearly polarized 11-ps pulses at 1064nm, with average power of 2.7 W at a 150-MHz repetition rate. Pulses as short as 7.9 ps were measured with reduced output power (1.35 W) by optimal focusing in the nonlinear crystal.     

High-power diode-end-pumped Nd:YVO4 laser: thermally induced fracture versus pump-wavelength sensitivity

We report two kinds of compact and efficient diode-end-pumped TEM₀₀ lasers with output power >25 W at ≈50 W of incident pump power. One laser consists of a single 0.3 at. % Nd:YVO₄ crystal in a V-type cavity, the other laser includes two 0.5 at. % Nd:YVO₄ crystals in a linear cavity. Experimental results show that lowering Nd³⁺ concentration can be beneficial in extending the fracture-limited pump power but it also increases the sensitivity of the pump wavelength due to the overlapping efficiency. Received: 19 February 2000 / Revised version: 30 May 2000 / Published online: 20 September 2000     

High-power air-cooled SiC-clad Nd:YVO4 slab lasers

We demonstrate a diode-pumped, air-cooled, 100 W class SiC-clad Nd:YVO(4) active slab laser based on diffusion bonding of two SiC plates to a thin Nd:YVO(4) slab. We obtained 83 W of cw output power with a slope efficiency of 27% without water cooling. This demonstration initiates a novel (to the best of our knowledge) cooling design for efficient removal of waste heat generated from the diode edge-pumped high-power slab laser at room temperature.     

Compact efficient all-solid-state eye-safe laser with self-frequency Raman conversion in a Nd:YVO4 crystal

An efficient compact eye-safe laser at 1525 nm is presented by use of self-frequency Raman conversion in a diode-pumped actively Q-switched Nd:YVO4 1342-nm laser. At an incident pump power of 13.5 W, the self-stimulated Raman laser produces 1.2 W of 1525-nm average output power at a repetition rate of 20 kHz. The corresponding peak power at 1525 nm is generally greater than 10 kW for repetition rates from 5 to 20 kHz.     

High-power diode-pumped Q-switched intracavity frequency-doubled Nd:YVO4 laser with a sandwich-type resonator

A compact and efficient diode-pumped acousto-optically Q -switched intracavity frequency-doubled Nd:Y VO(4)/KTP green laser is demonstrated. With 0.5-at. % Nd:Y VO(4), greater than 4.6 W of 532-nm average power at a repetition rate of 50 kHz was generated with 17-W pump power, corresponding to a conversion efficiency of 27%. At 10-30 kHz the pulse width is shorter than 10 ns, and the peak power is higher than 13 kW.     

High-power diode-pumped actively Q-switched Nd:YVO4 self-Raman laser: influence of dopant concentration

Efficient self-Raman frequency conversion from a diode-pumped actively Q-switched Nd:YVO4 laser at 1064 nm to Stokes emission at 1176 nm is achieved for the first time to the author's knowledge. With a 0.2-at.% Nd:YVO4 crystal, greater than 1.5 W of power at a wavelength of 1176 nm at a repetition rate of 20 kHz was generated with a diode pump power of 10.8 W, corresponding to a conversion of 13.9%. Pulse width and peak power were 18 ns and 4.2 kW, respectively.     

A 15.1 W continuous wave TEM00 mode laser using a YVO4/Nd:YVO4 composite crystal

A effective continuous-wave (CW), high power laser generated using a YVO₄/Nd:YVO₄ composite crystal is presented. 18.8 W output power in multi-mode has been achieved with a maximum absorbed pump power of 31.2 W, corresponding to an optical-to-optical efficiency of 60.26%. In TEM₀₀ mode operation, 15.1 W output power also has been achieved with the maximum absorbed pump power of 31.2 W, corresponding to an optical-to-optical efficiency of 47.69%. With a 200 mm focal-length positive lens and using the moving knife-edge method, the beam quality factor is measured to be M² = 1.2 for TEM₀₀ mode beam.     

Frequency-stabilized Nd:YVO4 thin-disk laser

We have developed a Nd:YVO₄ thin-disk laser at 914 nm with single-frequency operation and active frequency stabilization to a low-finesse reference cavity. The spectral density of laser frequency noise is analysed by means of noise measurements at the error point of the frequency control loop. To address the 3¹S₀→3³P₁ magnesium intercombination line at 457 nm, we use an external frequency doubling stage based on periodically poled KTiOPO₄ for the generation of more than 150-mW output power at 457 nm. Optical beat signal measurements at 457 nm with a frequency-stable dye laser show a short-time line width of the thin-disk laser of less than 100 kHz. PACS 42.55.Xi; 42.60.Lh; 42.62.Fi; 42.65.Ky     

高效率多程折叠Nd:YVO4激光放大器

采用具有近共焦、非稳腔特点的多程折叠光路结构,使激光光束多次通过增益介质,实现了高提取效率的激光放大器.实验中在注入22W种子激光的条件下,以43.9%的提取效率得到了63 W的激光输出,斜效率超过52%,激光放大器的输出光束质量从种子激光的M2X=2.08,M2Y=1.92变为M2X=2.84,M2Y=1.79.     

LD连续泵浦Nd:YVO4声光调Q激光器

利用半导体激光器（LD）连续单端泵浦Nd:YVO4晶体,实现了声光调Q输出1 064nm的短脉冲。分析并用实验验证了不同透过率输出耦合镜及不同重复频率条件下,输出调Q脉冲能量、脉冲宽度及平均输出功率的规律。在泵浦功率为20.7W,重复频率为50kHz时,获得了最大平均输出功率为5.72W的脉冲,光 光转换效率为28%,斜效率为32.4%;在重复频率为10kHz时,最大单脉冲能量为0.286mJ,脉宽为22ns,峰值功率为13kW。     

LD-pumped Q-switched Nd:YVO4 self-Raman laser

LD-pumped actively Q-switched Nd:YVO₄ self-Raman laser is presented. The maximum average output power of the self-Raman laser at 1173.6 nm was obtained to be 2.21 W at the incident pump power of 18 W and the pulse repetition frequency (PRF) of 30 kHz, with the corresponding optical conversion efficiency of 12.28%.     

LD连续泵浦Nd:YVO4声光调Q激光器

 利用半导体激光器（LD）连续单端泵浦Nd:YVO₄晶体，实现了声光调Q输出1 064nm的短脉冲。分析并用实验验证了不同透过率输出耦合镜及不同重复频率条件下，输出调Q脉冲能量、脉冲宽度及平均输出功率的规律。在泵浦功率为20.7W，重复频率为50kHz时，获得了最大平均输出功率为5.72W的脉冲，光 光转换效率为28%，斜效率为32.4%；在重复频率为10kHz时，最大单脉冲能量为0.286mJ，脉宽为22ns，峰值功率为13kW。