H. Kan

>1 MW peak power single-mode high-brightness passively Q-switched Nd 3+ :YAG microchip laser

A high-brightness diode end-pumped Nd:YAG microchip laser, passively Q-switched by a Cr(4+):YAG saturable absorber (SA), has been developed. The dependences of pulse energy and width were investigated based on theoretical verification to enhance the peak power. As a result, the peak power exceeded 1.2 MW with M(2) = 1.04 and spectrum width Delta lambda < 5.1 pm at a repetition rate of 100 Hz. Brightness of 98 TW/sr x cm(2) was obtained with a supplied average electrical power of 2.3 W. The peak power increased up to 2.1 MW with M(2) = 1.36. Peak power of 1.7 MW was obtained from a 2-cm-diameter x 5-cm-long monolithic laser head.

Polarization Stabilizing for Diode-Pumped Passively Q-Switched Nd:YAG Microchip Lasers

We have demonstrated the new way of the polarization stabilizing in the passively Q-switched laser by using a [110]-cut Cr4+:YAG crystal. The 355-nm ultra-violet light was generated with 32 % conversion efficiency from 1064 nm.

Passively Q-switched Nd:YAG microchip laser over 1-MW peak output power for micro drilling

We report a palm top size passively Q-switched Nd:YAG microchip laser capable of producing lineally polarized 1.7-MW peak-power. This high-brightness laser enables to realize the efficient frequency doubling for micro drilling to stainless plates.

Down-scattered neutron imaging detector for areal density measurement of inertial confinement fusion

A custom developed (6)Li glass scintillator (APLF80+3Pr) for down-scattered neutron diagnostics in inertial confinement fusion experiments is presented. (6)Li provides an enhanced sensitivity for down-scattered neutrons in DD fusion and its experimentally observed 5-6 ns response time fulfills the requirement for down-scattered neutron detectors. A time-of-flight detector operating in the current mode using the APLF80+3Pr was designed and its feasibility observing down-scattered neutrons was demonstrated. Furthermore, a prototype design for a down-scattered neutron imaging detector was also demonstrated. This material promises viability as a future down-scattered neutron detector for the National Ignition Facility.

High power and high repetition Nd:YAG laser pumped by cw LDs

We have been developing a high repetition (5 kHz) and high power (5 kW) Nd:YAG laser system for EUV lithography. Key subjects are (1) reliable front-end, (2) uniform and high density pumping of main amplifier rods, and (3) compensation of thermal effects. Fairly good uniformity was achieved by adjusting pumping geometry. Detail system analysis suggests that 8 amplifier modules pumped at 24.0 kW power are required to get output of 5 kW under relatively small thermal effects.

Development of cryogenic TGG ceramic based Faraday rotator for inertial fusion driver

As the first demonstration of Faraday effect with a TGG ceramics, the Verdet constant was experimentally evaluated to be 36.4 rad/Tm at 1053 nm, which is same as that of the single crystal. The Verdet constant was improved for 87 times greater than that at room temperature. The measured thermal conductivity was corresponding to TGG single crystal between 100 K and room temperature. We have confirmed the feasibility of Faraday material for IFE driver by use of cryogenic TGG ceramics.

Diode-pumped passively Q-switched high-brightness microchip lasers

We have demonstrated the diode end-pumped high-brightness Nd3+:YAG microchip lasers, passively Q-switched by Cr4+:YAG as a saturable absorber (SA). In order to optimize the output characteristic of the laser, we have investigated the transmission of Cr4+:YAG, and acquired the dependence of the pulse energy density on the initial transmission with the final transmission that was provided from the measurement. As a result, its maximum output pulse energy was 0.95 mJ with the pulse width of 480 ps and the peak power was 1.7 MW and a beam quality was M2= 1.05 with 100 Hz repetition frequency.

Demonstration of high energy-extraction efficiency in a novel laser-diode pumped eight-pass Nd:YAG zig–zag slab amplifier

Abstract A novel laser-diode pumped eight-pass Nd:YAG zig–zag slab amplifier architecture was developed with the aim of achieving high energy-extraction efficiency. High energy-extraction efficiency of up to 71% for the laser mode volume has been achieved in this amplifier operating at an initial small signal gain of 3.25. The compensation of thermal birefringence in this amplifier was successfully performed.

High order wavefront correction for a 1 joule class Nd:YLF rod amplifier by phase conjugate plate

Wavefront correction until Zernike polynomial of degree three by a phase conjugate plate has been demonstrated in a high-energy Nd:YLF amplifier system. 108, amplification of 380 mJ has been achieved with a near-diffraction-limited beam quality.

High order wavefront correction for high-energy Nd:YLF rod amplifier by phase conjugate plate

Wavefront correction until Zernike polynomial of degree three by a phase conjugate plate has been demonstrated in a high-energy Nd:YLF amplifier system. 108 amplification of 380 mj has been achieved with a near-diffraction-limited beam quality.