Joule-class sub-nanosecond pulses produced by end-pumped direct bonded YAG/sapphire modular amplifier.

A Joule-class room-temperature diode-pumped solid-state laser was developed. The energy scaling of the 100 mJ 1064 nm seed pulse was realized by a series of two diode-pumped amplifiers. The gain medium consists in free combinations of Nd:YAG ceramics bonded to sapphire transparent heat sinks, to relax the thermal load induced by the 34 kW pump power. At low repetition rate, parasitic lasing was the main limitation to energy scaling. By choosing a gain module combination producing a step-like gradual doping concentration profile, mitigation of parasitic oscillations was observed, and the system delivered 2.8 J, 800 ps pulses at 2 Hz.

Laser-induced damage study of bonded material for a high-brightness laser system.

In this work we evaluated the laser-induced damage threshold of the interface between two identical YAG crystals, bonded by an inter-layer assisted surface activated bonding method. The experimental results indicate slight damage threshold degradation for both single- and polycrystalline trivalent rear-earth (RE3+)-ion-doped YAG gain media in the sub-nanosecond pulse regime. Moreover, crystal annealing prior to damage testing could provide additional improvement for the laser damage threshold of the bulk and bonded interface.

High peak-power near-MW laser pulses by third harmonic generation at 355†nm in Ca5(BO3)3F nonlinear single crystals.

In this work, the performance of Ca5(BO3)3F (CBF) single crystals was investigated for the third harmonic generation at 355 nm. A high energy conversion efficiency of 16.9% at 355 nm was reached using a two-conversion-stage setup. First, using a high peak power, passively Q-switched Nd3+:YAG/Cr4+:YAG microlaser based gain aperture in micro-MOPA, the second harmonic at 532 nm was achieved with lithium triborate (LBO) crystal, reaching 1.35 MW peak power. On a second step, laser pulses at 355 nm were generated using a 5 mm-long CBF crystal growth by TSSG method with energy, pulse duration and peak power of 479 µJ, 568 ps and 0.843 MW, respectively. These results are currently the highest reported for CBF material.

>30 MW peak power from distributed face cooling tiny integrated laser.

The Distributed Face Cooling (DFC) chip was fabricated from four pieces of 1 mm-length Nd:YAG plate sandwiched in four pieces of sapphire heat spreaders through advanced surface activated bonding (SAB) at room temperature. A sub-nanosecond (665.7ps) pulsed DFC-chip tiny integrated laser was achieved with output energy of 21.5 mJ and peak power of 32.3 MW with saturable absorber Cr4+:YAG. By finite element analysis, we confirmed the advantages of heat dissipation from DFC-chip compared with conventional bulk-chip. The SAB-DFC-chip based ubiquitous high peak power tiny integrated laser was experimentally within reach for laser-armed robot.

Temperature stable operation of YCOB crystal for giant-pulse green microlaser.

In this work the performance of two yttrium calcium oxyborate (YCOB) crystals made by Czochralski and Bridgman growth process was measured. By using high peak power, passively Q-switched Nd3+:YAG/Cr4+:YAG microlaser, high conversion second harmonic generation efficiency were obtained. Laser pulses at 532 nm with 1.14 mJ energy and 223 ps duration were obtained with a 15-mm long YCOB crystal that was grown by Bridgman method. The conversion efficiency was 70.2%, comparable with the conversion efficiency of 72.8% that was achieved with 10-mm long lithium triborate (LBO) nonlinear crystal. Also, for the first time, experimental data on temperature tuning in type I YCOB crystal was measured with linear slope in 200°C temperature range equal to -0.057%/°C and -0.064%/°C for the Czochralski and Bridgman grown crystals, respectively. Such YCOB nonlinear crystal can become a serious option for developing laser sources with high-peak power at high repetition rate that can operate in harsh environment.

Giant-pulse Nd:YVO4 microchip laser with MW-level peak power by emission cross-sectional control.

We present a giant-pulse generation laser realized by the emission cross-section control of a gain medium in a passively Q-switched Nd:YVO4 microchip laser with a Cr4+:YAG saturable absorber. Up to 1.17 MW peak power and 1.03 mJ pulse energy were obtained with a 100 Hz repetition rate. By combining the Nd:YVO4 crystal with a Sapphire plate, lower temperature difference between a pump region in the gain crystal and a crystal holder was obtained which helped to keep the cavity in stability zone at elevated temperatures and allowed the achievement of the high peak power for this laser system.

>MW peak power at 266 nm, low jitter kHz repetition rate from intense pumped microlaser.

Intense pulse pumped microlaser is proposed for high peak power and low timing jitter at high repetition rate. It is based on Intense and Fast Pulse Pump (IFPP) technique, in which fast pulse pumps up the upper-level population and then dumps it rapidly by Q-switching. That could come close to complete pumping efficiency to reduce thermal problems and contribute to suppress the timing jitter of passively Q-switched laser. In this work, linearly polarized 1064 nm beam from [100]-cut YAG/Nd3+:YAG and [110]-cut Cr4+:YAG passively Q-switched microlaser is directly guided into nonlinear crystals to obtain 532 nm and 266 nm output. By implementing IFPP concept, over 1 MW peak power, 215 ps pulse duration, 1 kHz pulses at 266 nm with reduced standard deviation timing jitter of 37 ns were obtained.