The relationship between the laser damaged threshold and step velocity in different supersaturation regions.

The laser damaged threshold (LDT) of potassium dihydrogen phosphate (KDP) crystals grown at different supersaturation points were investigated using a Nd:YAG nanosecond laser. The growth rate was measured by a laser polarization interference system. Combining the step slopes, the dependence of v-(σ) was obtained. It is interesting that the dependence of LDT-(σ) can also be divided into three areas and shows a similar dependence to that of v-(σ). The LDT reduces rapidly at the transition supersaturation area, and has the lowest value at σ = 0.07. In different supersaturation regions, the micro morphology of the KDP crystals was observed using an atomic force microscope. The nature of the step movement and bunching together of steps may contribute to the dependence of LDT-(σ).

Single frequency MOPA based on Nd:YAG single crystal fiber and rods.

We demonstrate a single frequency 1064 nm master oscillator power amplifier (MOPA) system operating in macro-micro pulse scheme. The repetition rate for the macro pulses was 300 Hz with pulse duration of 300 µs. Micro pulses operated at 25 kHz. The master laser was a single-longitudinal-mode electro-optically Q-switched Nd:YAG laser with an output power of 250 mW and pulse duration of 33 ns. Three stages of power amplifiers based on Nd:YAG single crystal fiber and rods were designed. The final output power reached 31.3 W with pulse duration of 30 ns and linewidth of less than 130 MHz. Micro pulse energy of 13.9 mJ was obtained with a peak power of up to 464 kW. The beam quality factors (M2) were measured to be 1.56 and 1.76 in horizontal and vertical directions, respectively.

High power broadband LiF:F(2)(-) color center laser.

A high power LiF:F(2)(-) color center laser is demonstrated with broadband emission. The excitation source is a quasi-continuous wave diode side-pumped acousto-optically Q-switched Nd:YAG laser. Under an incident 1064-nm laser power of 25.4 W, the highest output power of up to 4.7 W is obtained with a macro pulse repetition rate of 400 Hz and a micro pulse repetition rate of 50 kHz. The broadband emission is centered at 1142 nm with a bandwidth of 13 nm.

Single-frequency CaWO4 Raman amplifier at 1178 nm.

Single-frequency crystalline Raman amplifications at 1178 nm were demonstrated. The seeding laser was generated from a single-frequency continuous wave fiber Raman amplifier. Three stages of Raman amplifications from CaWO4 single crystals were realized with a pulsed 1064 nm Nd:YAG laser as the pumping source. The final output pulse energy at 1178 nm was 26.7 mJ, and the pulse width was 2.9 ns, corresponding to a peak power of 5.2 MW. The overall Raman amplification ratio was up to 4.6×10(6). The linewidth was less than 500 MHz.

Multiple-beam output of a surface-emitted terahertz-wave parametric oscillator by using a slab MgO:LiNbO3 crystal.

A MgO:LiNbO3 slab configuration for the surface-emitted terahertz-wave parametric oscillator (TPO) is presented. The pump and the oscillating Stokes beams were totally reflected at the slab surface and propagated zigzaggedly in the slab MgO:LiNbO3 crystal. Up to five terahertz beams were emitted perpendicularly to the surface of the crystal. The total output energy of the five THz-wave beams was 3.56 times as large as that obtained from the conventional surface-emitted TPO at the same experimental conditions. The intensity distributions of the THz wave beams were measured, and they were unsymmetrical in the horizontal direction while symmetrical in the vertical direction.