We present the design for a high-speed adaptive optics system that will be used to achieve the necessary laser pointing and beam-quality performance for initial fast-ignition coupling experiments. This design makes use of a 32×32 pixellated MEMS device as the adaptive optic and a two-channel interferometer as the wave-front sensor. We present results from a system testbed that demonstrates improvement of the Strehl ratio from 0.09 to 0.61 and stabilization of beam pointing from ∼75μrad to <2μrad.

Several techniques have been developed to phase apertures in the context of astronomical telescopes with segmented mirrors. Phasing multiple apertures, however, is important in a wide range of optical applications. The application of primary interest in this paper is the phasing of multiple short pulse laser beams for fast ignition fusion experiments. In this paper analytic expressions are derived for parameters such as the far-field distribution, a line-integrated form of the far-field distribution that could be fit to measured data, enclosed energy or energy-in-a-bucket and center-of-mass that can then be used to phase two rectangular apertures. Experimental data is taken with a MEMS device to simulate the two apertures and comparisons are made between the analytic parameters and those derived from the measurements. Two methods, fitting the measured far-field distribution to the theoretical distribution and measuring the ensquared energy in the far-field, produced overall phase variance between the 100 measurements of less than 0.005 rad(2) or an RMS displacement of less than 12 nm.

We have commissioned a turnkey 500 mJ, 10 Hz front end laser. The system delivers temporally and spectrally tailored pulses to correct signal distortions within itself or subsequent amplifiers from single longitudinal mode to 250 GHz RF bandwidth.

The laser is nearing completion with demonstration of 73% frequency-conversion efficiency, deformable mirror operation that generated a 4-times diffraction limited spot, and commissioning of an advanced front end to be installed on the main laser.

We have produced over 500 mJ using a hybrid fiber-based master-oscillator system coupled with a Yb:S-FAP power amplifier. This system is designed with spatial, temporal, and spectral sculpting enabling broadband amplification correctable for gain narrowing.

Hundred-joule, kilowatt-class lasers based on diode-pumped solid-state technologies, are being developed worldwide for laser-plasma interactions and as prototypes for fusion energy drivers. The goal of the Mercury Laser Project is to develop key technologies within an architectural framework that demonstrates basic building blocks for scaling to larger multi-kilojoule systems for inertial fusion energy (IFE) applications. Mercury has requirements that include: scalability to IFE beamlines, 10 Hz repetition rate, high efficiency, and 10(9) shot reliability. The Mercury laser has operated continuously for several hours at 55 J and 10 Hz with 2 fourteen 4 x 6 CM ytterbium doped strontium fluoroapatite amplifier slabs pumped by eight 100 kW diode arrays. A portion of the output 1047 nm was converted to 523 nm at 160 W average power with 73 % conversion efficiency using yttrium calcium oxy-borate (YCOB).

We report on the operation of the Mercury laser with fourteen 4 × 6 cm 2 Yb:S-FAP amplifier slabs pumped by eight 100 kW peak power diode arrays. The system was continuously run at 55 J and 10 Hz for several hours, (2 × 10 5 cumulative shots) with over 80% of the energy in a 6 times diffraction limited spot at 1.047 μm. Improved optical quality was achieved in Yb:S-FAP amplifiers with magneto-rheological finishing, a deterministic polishing method. In addition, average power frequency conversion employing YCOB was demonstrated at 50% conversion efficiency or 22.6 J at 10 Hz.

The Mercury laser operated continuously for several hours at 55J and 10Hz with fourteen 4×6 cm2 Yb:S-FAP amplifier slabs pumped by eight 100kW diode arrays. Average power frequency conversion employing YCOB yielded 50% conversion efficiency.

The Mercury laser project is part of a national inertial fusion energy program in which four driver technologies are being considered including solid-state lasers, krypton fluoride gas lasers, Z-Pinch and heavy ions. Mercury's operational goals of 100 J, 10 Hz, 10% efficiency in a 5 times diffraction limited spot will demonstrate the critical technologies required for scaling the system to the multi-kilojoule level. Five one hour runs were conducted to assess system stability and reliability; energy fluctuations during the 55 J operations showed a 0.6% rms deviation. Current beam quality during average power operation is approximately 10 times diffraction limited. In the future, active wavefront control, and corrector plates for steady state thermal distortions will be implemented to achieve the 5 times diffraction limited spot.

We report initial operation of the Mercury laser with seven 4 x 6 cm S-FAP amplifier slabs pumped by four 80 kW diode arrays. The system produced up to 33.5 J single shot, 23.5 J at 5 Hz, and 10 J at 10 Hz for 20 minute runs at 1047 nm. During the initial campaign, more than 2.8 x 10(4) shots were accumulated on the system. The beam quality of the system was measured to be 2.8 x 6.3 times diffraction limited at 110 W of output, with 96% of the energy in a 5X diffraction limited spot. Static wavefront glass plates were used to correct for the low order distortions in the slabs due to fabrication and thermal loading. Scaling of crystal growth has begun with the first full size slab produced from large diameter growth. Using an energetics optimization code we find the beam aperture is scalable up to 20 x 30 cm and 4.2 kJ.

A new family of laser diode packages has been developed using silicon V-groove technology. Different versions of the package that tradeoff simplicity and performance for applications requiring low duty factor and high peak power operation, or high duty factor and high average power operation, have been demonstrated.

A monolithic microchannel-cooled laser diode array is demonstrated that allows multiple diode-bar mounting with negligible thermal cross talk. The heat sink comprises two main components: a wet-etched Si layer that is anodically bonded to a machined glass block. The continuous wave (cw) thermal resistance of the 10 bar diode array is 0.032 °C/W, which matches the performance of discrete microchannel-cooled arrays. Up to 1.5 kW/cm2 is achieved cw at an emission wavelength of ∼808 nm. Collimation of a diode array using a monolithic lens frame produced a 7.5 mrad divergence angle by a single active alignment. This diode array offers high average power/brightness in a simple, rugged, scalable architecture that is suitable for large two-dimensional areas.

InGaAsP/InP laser bars with an emission wavelength of 1.73 {micro}m have been fabricated using compressively-strained multiple-quantum-well separate-confinement heterostructures. One-cm-wide, 0.7-fill-factor, diode bars are bonded onto Si microchannel heatsinks. A maximum cw power of 16 W was produced from a one-cm bar. Derated to SW cw, the extrapolated lifetime is 10,000 hours of operation with a 20% degradation in output power. A 10-bar microlensed diode array with a one-square-cm aperture produced 200 W of peak power and was focused onto a Cr:ZnSe slab laser. Over 3 watts of pulsed power and xxmw of average power was generated at a wavelength of 2.5 {micro}m.

We derive approximate expressions for transient output power and wavelength chirp of high-peak-power laser-diode bars assuming one-dimensional heat flow and linear temperature dependences for chirp and efficiency. The model is derived for pulse durations, 10 less than (tau) less than 1000 microseconds, typically used for diode-pumped solid-state lasers and is in good agreement with experimental data for Si heatsink mounted 940 nm laser-diode bars operating at 100 W/cm. The analytic expressions are more flexible and easily used than the results of operating point dependent numerical modeling. In addition, the analytic expressions used here can be integrated to describe the energy per unit wavelength for a given pulse duration, initial emission bandwidth and heatsink material. We find that the figure-of-merit for a heatsink material in this application is ((rho) CpK)1/2 where (rho) Cp is the volumetric heat capacity and K is the thermal conductivity. As an example of the utility of the derived expressions, we determine an effective absorption coefficient as a function of pump pulse duration for a diode-pumped solid-state laser utilizing Yb:Sr5(PO4)3F (Yb:S-FAP) as the gain medium.

In high-peak-power diode-pumped solid-state laser systems, diode chirp and sag during the pump pulse can play a major role in determining the pump energy absorbed in the laser medium. For pulse durations, 10 < τ < 1000 μs, typically used for diode-pumped solid-state lasers, we find that transient output power and wavelength chirp of high-peak-power laser-diode bars can be modeled assuming one-dimensional heat flow and linear temperature dependences for chirp and efficiency. The model is in good agreement with experimental data for Si heatsink mounted 940 nm laser-diode bars operating at an initial power of 100 W/cm. The figure-of-merit for a heatsink material in this application is (ρCpK)1/2 where ρCp is the volumetric heat capacity and K is the thermal conductivity. As an example of the utility of the derived expressions, we determine an effective absorption coefficient as a function of pump pulse duration for a diode-pumped solid-state laser utilizing Yb:Sr5(PO4)3F (Yb:S-FAP) as the gain medium.

Applications using high energy ''petawatt-class'' laser drivers operating at repetition rates beyond 0.01 Hz are only now being envisioned. The Mercury laser system is designed to operate at 100 J/pulse at 10 Hz. We investigate the potential of configuring the Mercury laser to produce a rep-rated, ''petawatt-class'' source. The Mercury laser is a prototype of a high energy, high repetition rate source (100 J, 10 Hz). The design of the Mercury laser is based on the ability to scale in energy through scaling in aperture. Mercury is one of several 100 J, high repetition rate (10 Hz) lasers sources currently under development (HALNA, LUCIA, POLARIS). We examine the possibility of using Mercury as a pump source for a high irradiance ''petawatt-class'' source: either as a pump laser for an average power Ti:Sapphire laser, or as a pump laser for OPCPA based on YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB), ideally producing a source approaching 30 J /30 fs /10 Hz--a high repetition rate petawatt. A comparison of the two systems with nominal configurations and efficiencies is shown in Table 1.