Fumiaki Matsuoka

Nd:YAG oscillator–amplifier system with a passive ring self-pumped phase-conjugate mirror

A ring self-pumped phase-conjugate mirror with rhodium-doped barium titanate is used to correct aberrations in a laser-diode-pumped zigzag slab Nd:YAG oscillator-amplifier system. A diffraction-limited output of 360 mJ is achieved in a 36-ns pulse duration at a repetition rate of 100 Hz.

High-repetition rate 1-J green laser system

A laser-diode-pumped high-repetition-rate zigzag slab Nd:YAG oscillator-amplifier system is developed as the pumping source of a high-average-power and terawatt Ti:sapphire chirped pulse amplification laser system. This system can produce a greater than 2-J high-energy fundamental laser pulse at a repetition rate of 100 Hz. The frequency-doubled energy with a diffusion-bonded KTP crystal is 1 J at a repetition rate of 100 Hz.

High-repetition-rate 2-J Nd:YAG oscillator-amplifier system

Advances in high-repetition-rate high-average-power ultrashort-pulse laser systems1–3 are expected to be utilized in many applications, such as higher-harmonic generation4 and material processing,5 that require high average flux. However, the average power of such systems is still limited to several watts because the average power of pump sources has been limited to tens of watts.

Diffusion Bonded KTiOPO4 Crystal for the Second Harmonic Generation of High Average Power Zigzag Slab Nd:YAG Laser

For the second harmonic generation (SHG) of a high-repetition rate and high pulse energy zigzag slab Nd:YAG laser, the direct bonding of two KTiPO4 (KTP) crystals is carried out and their characteristics are studied using the zigzag slab laser that produces 2.1 J energy pulses with a beam having a rectangular cross section at a pulse repetition rate of 100 Hz. Although an angle mismatch of four minutes between two tuning curves is observed for the bonded crystals, the energy conversion efficiency is the same as that of a single KTP crystal. The second harmonic produced is 1 J.

Photorefractive phase conjugator for Nd:YAG laser system

Abstract An external loop phase conjugate mirror with a 45°-cut rhodium-doped BaTiO3 is constructed and characterized. The external loop is composed of an image-relay telescope, a 90°-image rotator and a phase modulator. An Nd:YAG laser with the phase conjugate mirror produces a pulse energy of 330 mJ at 100 Hz with a beam quality of 1.2×DL.

Through-hole processing of aluminum nitride and silicon wafers using short-pulse lasers

Compact short pulse (200 - 350 ps) laser systems using SBS and SRS pulse compression techniques have been constructed. Fine processing of aluminum nitride and silicon wafer has been studied by using these laser pulses and compared with the results processed by 60 femto second laser system. Through-holes are formed on wafers by irradiation of the laser pulses, and the relationship between hole shapes and the processing conditions has been studied. The hole shape relates with the focusing length of the lens, laser fluence, pulse width and the wave length. Trepanning technique has been examined also to improve the hole shape. The result is quite.

X-ray spectroscopic study on femto- and pico-second laser irradiated solid and gaseous targets

The soft x-ray emission from He-like and H-like were obtained by using the double nozzle gas-puff (Nitrogen, and Oxygen) target irradiated by the laser which delivered a laser energy of 50 mJ in 400 ps pulse width. Efficient absorption of the incident laser energy into the double gas-puff target was demonstrated experimentally such as 15%, and 29% for Nitrogen and Oxygen, respectively. The sub keV x-ray emission from He-β(1s2-1s2p, 1s2-1s3p, and 1s2-1s4p) lines are observed around the 0.4 nm wavelength region by using the double nozzle Argon gas-puff target irradiated by a 5 J, 1 ns, 1 μm laser. Using the gas-puff target irradiated by a femto-second laser pulse, highly ionized ions of Cr-, Fe- and Ni-like Kr at the 5 - 20 nm wavelength region have been observed in a laser produced plasma. However, the intensity of the x-ray emissions from double nozzle gas-puff target are lower than that from the single nozzle gas-puff targets, using the Krypton gas. Using xenon gas, the intensity of the x-ray emissions from double nozzle gas-puff target is equivalent to that from the single nozzle target.

Nd:YAG oscillator-amplifier with a photorefractive phase conjugator

A ring type self-pumped phase-conjugate mirror with rhodium- doped barium titanate is used to correct aberrations of an LD- pumped sigzag slab Nd:YAG oscillator-amplifier system. A diffraction limited output of 360 mJ is achieved at the repetition rate of 100 Hz.