J. H. Yu

456-nm deep-blue laser generation by intracavity frequency doubling of Nd:GdVO4 under 879-nm diode pumping

We report on a simple, compact continuous-wave 456-nm laser by intracavity frequency doubling of an end-pumped Nd:GdVO4 laser on the 4F3/2 → 4I9/2 transition. A 5-mm-long, 0.2-at % Nd:GdVO4 bulk crystal is employed as the gain medium and the Nd3+ ion is directly pumped into the emitting level (4F3/2) by a novel 879-nm laser diode. Intracavity frequency doubling with a 15-mm-long LBO crystal and a 10-mm-long BiBO crystal in a linear cavity yield 56- and 118-mW single-ended blue outputs at the absorbed pump power of 11.9 W, respectively. The corresponding values are scaled to 286 and 391 mW, respectively, in a V-type cavity, with optical conversion efficiencies of 2.4 and 3.3% versus the absorbed pump power. The fluctuations of the 456-nm output power for both cases are less than 3% at the maximum output level.

8.9-W continuous-wave, diode-end-pumped all-solid-state Nd:YVO4 laser operating at 914 nm

A high power laser-diode-array end-pumped 0.2 at % Nd:YVO4 continuous-wave (CW) laser operating at 914 nm is reported in this letter. The maximum output power of 8.9 W was obtained at the incident pump power of 48.0 W, giving the corresponding optical efficiency of 18.5% and the average slope efficiency of 25.7%. The beam quality factor was measured to be M2 = 2.71 at the output power of 8.0 W by the traveling knife-edge method.

High repetition rate, high peak power acousto-optical Q-switched 946 nm Nd:YAG laser

A diode-end-pumped high repetition rate, high peak power acousto-optical (AO) Q-switched 946 nm Nd:YAG laser was demonstrated in this paper. In our experiments, a 20 mm miniature acousto-optical Q-switch was employed in a 45 mm linear laser cavity for generating the short laser pulse. At a repetition rate of 10 kHz, a maximum average output power of 2.9 W was achieved with a pulse width of 24.4 ns, giving a peak power of 11.9 kW. To the best of our knowledge, this is the highest peak power 946 nm Nd:YAG laser at high repetition rate operation. Moreover, pulse train with good stability was also obtained at the repetition rate of 50 kHz. At an incident pump power of 22.3 W, up to an average output power of 3.5 W pulsed 946 nm laser was generated at 50 kHz with a pulse width of 69 ns, corresponding to an optical conversion efficiency of 15.7% and an average slope efficiency of 24.1%, respectively.

Diode-pumped short pulse passively Q-switched 912 nm Nd:GdVO4/Cr:YAG laser at high repetition rate operation

A diode-end-pumped passively Q-switched 912 nm Nd:GdVO4/Cr:YAG laser is demonstrated for the first time. In a concave-piano cavity, pulsed 912 nm laser performance is investigated using two kinds of Cr:YAG crystal with different unsaturated transmission (TU) of 95% and 90% at 912 nm as the saturable absorbers. When the TU = 90% Cr:YAG is used, as much as 2.6 W average output power for short pulsed 912 nm laser is achieved at an absorbed pump power of 34.0 W, corresponding to an optical efficiency of 7.6% and a slope efficiency of 20.3%. Moreover, 10.5 ns duration pulses and up to 2.3 kW peak power is obtained at the repetition rate around 81.6 kHz.

Laser performance of grown-together YVO4/Nd:YVO4 composite crystal at continuous-wave 914 nm

We demonstrated a diode-end-pumped continuous-wave 914 nm laser using a novel grown-together YVO4/Nd:YVO4 crystal for the first time. A maximum output power at 914 nm of 7.5 W with an optical-optical efficiency of 16.3% and a slope efficiency of 24.3% was obtained when the incident pump power was 46.2 W. The beam quality factor M2 was 3.2 at the output power of 6.0 W. The quality and specification of the grown-together composite YVO4/Nd:YVO4 crystal should be improved. Meanwhile, energy-transfer upconversion spectrum of the composite YVO4/Nd:YVO4 crystal laser was also investigated.

912 nm laser operation in diode-pumped grown-together composite Nd:GdVO4/GdVO4 crystal

Novel grown-together Nd:GdVO4/GdVO4 composite crystals were presented for the first time, which would be longitudinally pumped by 808 nm diode-laser to efficiently operate on continuous-wave (CW) 912 nm laser at room temperature. The maximum output power of 8.15 W at 912 nm laser was obtained successfully at the absorbed pump power of 28.0 W, giving the corresponding optical-to-optical conversion efficiency of 29.1% and the average slope-efficiency of 44.2%. Comparative experimental results show that the laser performance was influenced significantly by the Nd3+-doped concentration of the crystals, which would be optimized according to its energy-transfer upconversion (ETU) spectrum.

The influence of energy transfer upconversion on thermal loading in end-pumped Nd:GdVO4 laser

The influence of energy transfer upconversion on thermal loading in end-pumped Nd:GdVO4 laser was investigated. The dependence of thermal loading on absorbed pump power and pump radius was discussed. Higher absorbed pump power and smaller pump radius resulted in more serious ETU effect, which cause more extra thermal loading. The experimental results indicated that ETU effect in Nd:GdVO4 laser is a unneglectable mechanism to generate extra heat especially in end-pumped geometry

Improvement in the laser performances of an A-O Q-switched Nd:GdVO4 laser by direct-diode pumping into the emitting level

The laser performances of an A-O Q-switched Nd:GdVO4 laser are demonstrated under LD pumping at 808 and 879 nm, respectively. Results indicate that the pulse performances are improved markedly under 879-nm LD direct pumping. At a repetition rate of 100 kHz, a maximum average output power of 12.1 W, a pulse width of 20.3 ns, and a peak power of about 6 kW are reached under 879-nm pumping.

Passively Q-switched GdVO4/Nd:GdVO4 laser with Cr4+:YAG saturable absorber under direct 879 nm diode pumping to the emitting level

A passively Q-switched 1.06 μm laser with Cr4+:YAG saturable absorber by direct 879 nm diode pumping grown-together composite GdVO4/Nd:GdVO4 crystal to the emitting level was demonstrated in this paper. The characteristics of pulsed laser were investigated by using two kinds of Cr4+:YAG crystal with the initial transmissivity of 80 and 90%, respectively. When the T0 = 90% Cr4+:YAG was used, an average output power of 1.59 W was achieved at an incident pump power of 10 W. The pulse width and repetition rate were 64.5 ns and 170 kHz, respectively. The thermal lens effect of laser crystal was analyzed.

Improved performance of diode-end-pumped Nd:GdVO4 912 nm laser property with indium solder technology

A novel indium-solder technology is demonstrated to deal with the serious thermal dissipation problem in the 912 nm Nd:GdVO4 laser operation. By use of indium-solder between the laser rod and the heat-sink, the contact resistance is reduced by removing the air bubble and heat conducting silicon and the boundary heat transfer coefficient is raised. After the indium-solder was used, it is found that the temperature in the laser rod and the deformation in the pumping end surface are eased remarkably based on a simulation of finite element analysis. Experimental results show that the continuous-wave 912 nm laser performance is improved obviously, both in a plano-plano cavity and a plano-concave cavity.