Optical-to-optical conversion efficiencies of as high as 32% with a slope efficiency of 44% were obtained with a novel diode-bar, side-pumped laser cavity design. A slab geometry with a single, high-angle-of-incidence reflection was used to extract gain from near the pump face of a Nd:YVO(4) bar that absorbed strongly at the pump wavelength. Small-signal gains of greater than 8 cm(-1) and pulse energies of as much as 3.2 mJ were obtained in an almost TEM(00) mode. Aperturing effects by the laser rod were found to limit the effects of nonuniform gain on the laser mode.

A High Efficiency Diode-Pumped Nd:YVO 4 Slab Laser

We demonstrated >80 W picosecond output at a pulse repetition frequency of 100 MHz from a dual Nd:YVO4 amplifier laser system consisting of a phase-conjugate Nd:YVO4 bounce amplifier combined with a second diode-side-pumped Nd:YVO4 bounce amplifier. The output exhibited high quality spatial form with M2 7.4 MW with an average power of 78.5 W was also achieved at a pulse repetition frequency of 1.0 MHz.

Sub-100 W picosecond output from a phase-conjugate Nd:YVO 4 bounce amplifier

For years, solid-state lasers have replaced traditional systems in numerous laser applications. Now, fiber lasers bring the ultimate in solid-state reliability and operating convenience to applications in materials processing, telecom, sensing, and medicine and so on. Various configurations of continuous wave (cw), mode-locked, Q-switched, or singlefrequency lasers have been reported, offering a large variety in performance characteristics. Ytterbium-doped silica fiber lasers operating near 1 µm as well as erbium fibers at 1.5 µm have been among the most successful fiber lasers creating a great impact on many areas of technology. Current progresses in fiber lasers are associated with further scaling of the output power. In particular, such power scaling could be achieved through coherent combining of the beams delivered by a number of regular fiber sources. In this perspective, apart from the use of active fibers as a gain media, it has appeared that the unique and rather special properties of Yb-doped fibers discussed in this Chapter have still to be exploited in novel high-brightness all-fiber laser systems. The Chapter is dedicated to the effect of refractive index changes taking place in standard commercial Yb-doped optical fibers under diode pumping, and also to applications of this effect for coherent combining of fiber lasers. Being associated with changes of population of different ion states, the effect of refractive index changes (RIC) is essentially a side effect of the population inversion mechanism that is responsible for light amplification in lasers. The electronic and thermal RIC mechanisms, which are important both for laser crystals and glasses, are intensively investigated for several years. Correct understanding of these phenomena is vital for Yb-doped fiber lasers and amplifiers, whose performance characteristics rely on physical processes in the active medium. The Chapter includes remarkable amount of original experimental studies, theoretical modeling and demonstration of advanced fiber configurations. The structure of the Chapter is logical and easy to follow. Part 2 contains judicially selected background material to

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Resonantly Induced Refractive Index Changes in Yb-doped Fibers: the Origin, Properties and Application for all-fiber Coherent Beam Combining

The current trends in stimulated Brillouin scattering and optical phase conjugation are overviewed. This report is formed by the selected papers presented in the “Fifth International Workshop on stimulated Brillouin scattering and phase conjugation 2010” in Japan. The nonlinear properties of phase conjugation based on stimulated Brillouin scattering and photo-refraction can compensate phase distortions in the high power laser systems, and they will also open up potentially novel laser technologies, e.g., phase stabilization, beam combination, pulse compression, ultrafast pulse shaping, and arbitrary waveform generation.

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The Current Trends in SBS and phase conjugation

The beam combination method using stimulated Brillouin scattering phase conjugate mirrors (SBS-PCMs) is a promising technique for a high energy and high power laser output operating with a high repetition rate. The two-beam combined system was previously demonstrated with an amplitude dividing method. A four-beam combined laser system with amplitude dividing method is demonstrated in this work, and the phase stabilization experiment of this system is performed using the self phase control and the long-term stabilization technique. The phase differences between the SBS waves are stabilized with λ/30 and the fluctuation of the four-beam combined output energy is 6.16% during 2000 shots (200 s).

Phase stabilization of the amplitude dividing four-beam combined laser system using stimulated Brillouin scattering phase conjugate mirrors

An overview on current trends in stimulated Brillouin scattering and optical phase conjugation is given. This report is based on the results of the “Second International Workshop on stimulated Brillouin scattering and phase conjugation” held in Potsdam/Germany in September 2007. The properties of stimulated Brillouin scattering are presented for the compensation of phase distortions in combination with novel laser technology like ceramics materials but also for e.g., phase stabilization, beam combination, and slow light. Photorefractive nonlinear mirrors and resonant refractive index gratings are addressed as phase conjugating mirrors in addition.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/8305A06ED0CA6FD9A9145EF40CBD06B6/S0263034608000335a.pdf/div-class-title-trends-in-stimulated-brillouin-scattering-and-optical-phase-conjugation-div.pdf

Trends in stimulated Brillouin scattering and optical phase conjugation

We demonstrate a high average power ~4 ps output from a phase conjugate laser system based on a diode-side-pumped Nd:Gd0.6Y0.4VO4 bounce amplifier. An average output power of 16.2 W with a peak power of 210 kW was achieved. A corresponding extraction efficiency of 23% was measured.

Picosecond master-oscillator, power-amplifier system based on a mixed vanadate phase conjugate bounce amplifier.

A 78.5 W pico-second master-oscillator power-amplifier system based on a Nd:YVO4 bounce amplifier with a phase conjugator was demonstrated. The peak power of the output pulses was 8-11 MW in a pulse-repetition-frequency region of 0.7-1 MHz.

11 MW pico-second pulses with ≫70 W average power from a phase-conjugate Nd:YVO 4 bounce laser system

11 MW pico-second pulses with >70 W average power from a phase-conjugate Nd: YVO4 bounce laser system

We demonstrated a 44 W near diffraction-limited pico-second output from a phase-conjugate laser system in combination with a diode-side-pumped Nd:GdVO 4 booster amplifier. Peak power of 0.35 MW was achieved.

N. Shiba

Papers

Trends in stimulated Brillouin scattering and optical phase conjugation

Picosecond master-oscillator, power-amplifier system based on a mixed vanadate phase conjugate bounce amplifier.

11 MW pico-second pulses with ≫70 W average power from a phase-conjugate Nd:YVO 4 bounce laser system

11 MW pico-second pulses with >70 W average power from a phase-conjugate Nd: YVO4 bounce laser system

0.35 MW Pulses with 44 W Average Power from a Picosecond Phase-Conjugate Nd:GdVO 4 Laser System