High-power deep-ultraviolet light generation at 266†nm from frequency quadrupling of a picosecond pulsed 1064†nm laser with a Nd:YVO4 amplifier pumped by a 914†nm laser diode.

We report the generation of picosecond pulsed light at a 266 nm wavelength with an average power of 53 W. We developed a picosecond pulsed 1064 nm laser source with an average power of 261 W, a repetition rate of 1 MHz, and a pulse duration of 14 ps, using a gain-switched DFB laser diode as a seed laser and a 914 nm laser-diode-pumped Nd-doped YVO4 power amplifier. We achieved stable generation of 266 nm light with an average power of 53 W from frequency quadrupling using an LBO and a CLBO crystals. The amplified power of 261 W and the 266 nm average power of 53 W from the 914 nm pumped Nd:YVO4 amplifier are the highest ever reported, to the best of our knowledge.

Stable 10,000-hour operation of 20-W deep ultraviolet laser generation at 266†nm.

We report 10,000-hour stable operation of a 266-nm picosecond laser with an average power of 20 W. We have developed a narrow-linewidth, high-peak-power 1064-nm laser source with a repetition rate of 600 kHz, an average power of 129 W, a linewidth of 0.15 nm, and a pulse duration of 14 ps using a gain-switched DFB-LD as a picosecond pulse seed source and a four-stage power amplifier with an Nd:YVO4 crystal. A 266-nm laser with a maximum average power of 25.4 W was generated by frequency conversion using LBO and CLBO crystals and had a pulse duration of 8 ps and beam quality factor of 1.5 at 20W. To the best of our knowledge, we also demonstrated that the average power and the beam quality can be maintained for 10,000 hours for the first time. We have confirmed the durability of the developed deep ultraviolet laser for industrial applications.

High-power DUV picosecond pulse laser with a gain-switched-LD-seeded MOPA and large CLBO crystal.

We report the generation of a 266 nm deep ultraviolet (DUV) picosecond pulse with an average output power of 14 W by the fourth-harmonic generation (FHG) from two consecutive frequency-doubling stages of a 1064 nm pulse based on a gain-switched-laser-diode (LD)-seeded hybrid fiber/solid-state master oscillator and power amplifier (MOPA) system. Through the gain-switched operation of a narrow-spectral-linewidth distributed-feedback laser diode and by using a Yb-doped fiber and a two-stage ${\rm Nd}:{{\rm YVO}_4}$Nd:YVO4 solid-state amplifier, we achieved an average power of 46.5 W near the Fourier transform limit for a 13 ps pulse with a repetition rate of 200 kHz. The narrow linewidth pulse characteristics enabled highly efficient frequency conversion, and the efficiency of conversion from 532 to 266 nm was 54%, and from 1064 to 266 nm was 31%. The beam quality factor ${M^2}$M2 of the generated DUV pulse was below 1.2. The highly efficient FHG process resulted in appeasing thermal stress caused by nonlinear absorption in the crystal, and more than 5000 h of continuous operation were achieved without any power down or beam profile degradation.

Transverse-flow radio-frequency-excited amplifier seeded by a cavity-dumped CO2 laser for an extreme ultraviolet light source.

A transverse-flow radio-frequency-exited CO2 laser amplifier was evaluated by a short-pulse seed laser. We constructed a prototype transverse-flow amplifier for the extreme UV laser-produced-plasma source. The electrical power for the discharge was enhanced to 100 kW at a 100% duty cycle. A Q-switched cavity-dumped CO2 seed laser emitting 13 ns pulses with a repetition rate of 100 kHz was amplified along a fivefold optical path in the amplifier gain medium. As a result, the amplifier output an average power of 3.07 kW with an 8.5 W laser input. The electrical-to-optical efficiency was 3.1%, which was far higher than that of axial-flow amplifiers at the same laser input power. The pulse showed a slight stretch from an input duration of 13 ns to an output of 15 ns.

Efficient pulse amplification using a transverse-flow CO2 laser for extreme ultraviolet light source.

We constructed a master oscillator power amplifier CO2 laser system using a transverse-flow, RF-pumped CW CO2 laser. We carried out an amplification test at a 100% duty cycle of pumping discharge with the electrical input for the discharge up to 60 kW. An output power of 1.90 kW was achieved at the oscillator repetition rate of 100 kHz and the optical input power of 13 W. The electrical-to-optical efficiency was 3.1%.

Development of line-shaped optical system for green laser annealing used in the manufacture of low-temperature poly-Si thin-film transistors.

We have developed a new optical system that transforms the circle profile beam generated with near-Gaussian intensity distribution by a pulse green laser (YAG2omega laser; second harmonics of a Q-switched Nd:YAG laser) into a line-profile beam. For homogenization in the longitudinal direction, we employed a waveguide plate-type homogenizer. We successfully reduced interference fringes. In the width direction, the laser beam was focused up to the limited M2 value. This transformed beam has a uniform distribution to within 5% in the longitudinal direction, and it is approximately 100 mm long and 40 microm wide.

Diode-pumped 1 kW Q-switched Nd:YAG rod laser with high peak power and high beam quality.

We have demonstrated high-peak-power generation at 1 kW average power by applying an acousto-optic Q switch to a quasi-cw diode-pumped Nd:YAG master oscillator power amplifier. We achieved a maximum peak power of 2.3 MW by driving the Q switch in burst mode. The average repetition rate was 6 kHz. The corresponding beam quality was M2 = 9.