Andrey V. Okishev

High-contrast optical-parametric amplifier as a front end of high-power laser systems

A high-contrast preamplifier based on optical-parametric amplification with a short pump pulse is demonstrated. A gain larger than 10(5) and measurement-limited contrast higher than 10(11) are obtained over a large temporal range extending within less than 10 ps of the peak of the pulse, because of the high instantaneous parametric gain provided by a short pump pulse in a nonlinear crystal. The energy gain and high contrast of this preamplifier make it a good seed source for high-power laser systems.

OMEGA EP high-energy petawatt laser: progress and prospects

OMEGA EP (extended performance) is a petawatt-class addition to the existing 30-kJ, 60-beam OMEGA Laser Facility at the University of Rochester. It will enable high-energy picosecond backlighting of high-energy-density experiments and inertial confinement fusion implosions, the investigation of advanced-ignition experiments such as fast ignition, and the exploration of high-energy-density phenomena. The OMEGA EP short-pulse beams have the flexibility to be directed to either the existing OMEGA target chamber, or the new, auxiliary OMEGA EP target chamber for independent experiments. This paper will detail progress made towards activation, which is on schedule for completion in April 2008.

Intracavity-pumped Raman laser action in a mid-IR, continuous-wave (cw) MgO:PPLN optical parametric oscillator

Intracavity-pumped Raman laser action in a fiber-laser-pumped, single-resonant, continuous-wave (cw) MgO:PPLN optical parametric oscillator with a high-Q linear resonator has been observed for the first time to our knowledge. Experimental results of this phenomenon investigation will be discussed.

Highly stable, all-solid-state Nd:YLF regenerative amplifier

A diode-pumped Nd:YLF regenerative amplifier (regen) has been developed and is in use in the 60-beam, 30-kJ UV Omega laser systems driver line. The high stability, the compactness, and the reliability of this all-solid-state modular design are the key features of this concept. Stable, millijoule-level output-pulse energies with an overall gain of 10(9) have been demonstrated. Excellent long-term output-pulse-energy stability of better than 1% rms fluctuations has been achieved with excellent beam quality (<1% ellipticity).

Diode-pumped Nd:YLF master oscillator for the 30-kJ (UV), 60-beam OMEGA laser facility

The operational conditions of the OMEGA laser system require an extremely reliable and low-maintenance master oscillator. We have developed a diode-pumped, single-frequency, pulsed Nd:YLF laser for this application. The laser generates Q-switched pulses of /spl sim/160-ns duration and /spl sim/10-/spl mu/J energy content at the 1053-nm wavelength with low amplitude fluctuation, (<0.6% rms) and low temporal (build-up time) jitter (<7-ns rms). Amplitude and frequency feedback stabilization systems have been used for high long-term amplitude and frequency stability.

Spectral filtering in a diode-pumped Nd:YLF regenerative amplifier using a volume Bragg grating

Instrument-limited suppression of out-of-band Amplified Spontaneous Emission (ASE) is demonstrated in a Nd:YLF Diode-Pumped Regenerative Amplifier (DPRA) using a Volume Bragg Grating (VBG) as a spectrally selective reflective element. A VBG with 99.4% diffraction efficiency and 230-pm-FWHM reflection bandwidth produced a 43-pm- FWHM output spectral width in an unseeded DPRA compared to 150-pm FWHM in the same DPRA with no VBG. Instrument-limited ASE suppression is even observed when the DPRA seed pulse energy approaches the ASE background.

Fiber Front End With Multiple Phase Modulations and High-Bandwidth Pulse Shaping for High-Energy Laser-Beam Smoothing

The design and performance of a fiber front end delivering temporally shaped, phase-modulated optical pulses to a large-scale, high-energy laser system to demonstrate beam-smoothing concepts are presented. High-bandwidth LiNbO3 (lithium niobate) Mach-Zehnder modulators and arbitrary waveform generators temporally shape the power of the optical pulses. High-bandwidth, three-section LiNbO3 phase modulators precisely modulate the optical phase of the pulses at up to three microwave frequencies. Various calibration procedures and fail-safe systems are described. Sources of frequency-modulation-to-amplitude-modulation conversion, which can lead to unsafe operation of the high-energy laser system, are identified and compensated by amplitude and dispersion compensators.

Highly efficient room-temperature Yb:YAG ceramic laser and regenerative amplifier

A room-temperature, diode-pumped, pulsed Yb:YAG ceramic free-running laser with a 78% slope efficiency has been demonstrated. It has been shown that fine tuning of the mode diameter to the diameter of the pumped volume with a ratio of the pump to the mode diameter of 0.6 is important for achieving maximum laser efficiency with a Gaussian-like beam profile. A regenerative Yb:YAG ceramic amplifier with a maximum output energy of 14.5 mJ and a super-Gaussian beam profile is demonstrated.

Pulse-shaping system for the 60-beam, 30-kJ (UV) OMEGA laser

The optical pulse-shaping system for the 60-beam 30-kJ (UV) OMEGA fusion laser is capable of producing complex temporally shaped optical pulses for amplification and delivery to fusion targets. The pulse-shaping system consists of optical modulators driven by an optically activated electrical waveform generator. The electrical waveform generator consists of Si photoconductive switches, and variable impedance microstrip lines. Complex optical pulse shapes with 50 to 100 ps structure have been produced.

Optical Parametric Chirped-Pulse-Amplification Contrast Enhancement by Regenerative Pump Spectral Filtering

A method for fundamentally improving the temporal contrast of optical parametric chirped-pulse amplification (OPCPA) systems by using a volume Bragg grating to regeneratively filter the OPCPA pump spectrum is demonstrated for the first time.