ABSTRACT
The Laser Shock Station in the Dynamic Compression Sector (DCS) [Advanced Photon Source (APS), Argonne National Laboratory] links a laser-driven shock compression platform with high energy x-ray pulses from the APS to achieve in situ, time-resolved x-ray measurements (diffraction and imaging) in materials subjected to well-characterized, high stress, short duration shock waves. This station and the other DCS experimental stations provide a unique and versatile facility to study condensed state phenomena subjected to shocks with a wide range of amplitudes (to above â¼350 GPa) and time-durations (â¼10 ns-1 µs). The Laser Shock Station uses a 100 J, 5-17 ns, 351 nm frequency tripled Nd:glass laser with programmable pulse shaping and focal profile smoothing for maximum precision. The laser can operate once every 30 min. The interaction chamber has multiple diagnostic ports, a sample holder to expose 14 samples without breaking vacuum, can vary the angle between the x-ray and laser beams by 135°, and can translate to select one of the two types of x-ray beams. The x-ray measurement temporal resolution is â¼90 ps. The system is capable of reproducible, well-characterized experiments. In a series of 10 shots, the absolute variation in shock breakout times was less than 500 ps. The variation in peak particle velocity at the sample/window interface was 4.3%. This paper describes the entire DCS Laser Shock Station, including sample fabrication and diagnostics, as well as experimental results from shock compressed tantalum that demonstrate the facility's capability for acquiring high quality x-ray diffraction data.
ABSTRACT
Conventional lens-based image relays introduce radial group delay that significantly reduces focal-spot intensity of ultra-broadband short pulses. A direct compensation scheme that can be used with conventional singlet image relays is proposed. The compensation scheme is based on using two negative lenses embedded within an Offner imaging system. The setup allows a single-pass configuration and eliminates the need for polarization switching optics. The performance of this setup is calculated using ray tracing. The compensation improves the spatiotemporal Strehl ratio from 0.02 to 0.97.
ABSTRACT
Spatially resolved spectral interferometry is used to measure the mode content of a Yb-doped photonic-crystal fiber rod amplifier with a 2300 µm(2) mode area. The technique, known as S(2) imaging, was adapted for the short fiber amplifier at full power and revealed a small amount of a copolarized LP(11) mode. Simulations illustrate the potential for weak mode suppression in this fiber and agree qualitatively with the measurements of S(2) and M(2). Higher-order-mode content depends on the alignment of the input signal at injection and ranged from -18 dB for optimized alignment to -13 dB when the injection alignment was offset along the LP(11) axis by 30% of the 55 µm mode-field diameter.
ABSTRACT
A high-resolution, high-precision beam-shaping system for high-power-laser systems is demonstrated. A liquid-crystal-on-silicon spatial light modulator is run in closed-loop to shape laser-beam amplitude and wavefront. An unprecedented degree of convergence is demonstrated, and important practical issues are discussed. Wavefront shaping for the applications in OMEGA EP laser is demonstrated, and other interesting examples are presented.
ABSTRACT
We characterize spatiotemporal aberrations induced in noncollinear optical parametric amplifiers (NOPAs), for the first time (to our knowledge), using spatially resolved spectral interferometry. Measurements show that when the submillimeter pump and signal beams are not correctly aligned, several degrees of pulse-front tilt caused by angular dispersion are introduced by the NOPA angular-dependent gain, without significant loss of bandwidth. After eliminating the pulse-front tilt, analysis of the residual higher-order aberrations shows that far-field intensities reaching 80% of the theoretical limit can be achieved without complex spatiospectral phase optimization.
ABSTRACT
A spot-shadowing technique to mitigate damage growth in a high-energy laser is studied. Its goal is to minimize the energy loss and undesirable hot spots in intermediate planes of the laser. A nonlinear optimization algorithm solves for the complex fields required to mitigate damage growth in the National Ignition Facility amplifier chain. The method is generally applicable to any large fusion laser.
ABSTRACT
We present an on-shot focal-spot characterization technique based on a phase-retrieval scheme that retrieves near-field phase from multiplane focal-spot measurements in an experimental target chamber. The technique is easy to implement inside a target chamber and is demonstrated in a multiterawatt laser system. It is also found that phase retrieval can quantitatively detect residual angular dispersion coming from the pulse compressor misalignment.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
A 250 mJ, 5 Hz repetition rate optical parametric chirped-pulse amplifier with near-Fourier-transform-limited, 430 fs pulses and a beam that can be focused to near the diffraction limit is demonstrated. A pump laser with engineered spatial and temporal profiles allows an overall pump-to-signal conversion efficiency of 34% to be achieved.
ABSTRACT
A high-energy, high-average-power laser system, optimized to efficiently pump a high-performance optical parametric chirped-pulse amplifier at 527 nm, has been demonstrated. The crystal large-aperture ring amplifier employs two flash-lamp-pumped, 25.4-mm-diameter Nd:YLF rods. The transmitted wave front of these rods is corrected by magnetorheological finishing to achieve nearly diffraction-limited output performance with frequency-doubled pulse energies up to 1.8 J at 5 Hz.
ABSTRACT
A diode-pumped Nd:YLF regenerative amplifier (regen) has been developed and is in use in the 60-beam, 30-kJ UV Omega laser system's 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).
ABSTRACT
We report a ytterbium fiber laser mode locked at its 281st harmonic, which corresponds to a repetition rate greater than 10 GHz. The laser produces linearly polarized, 2-ps pulses with up to 38-mW of average output power. The mode-locked pulses are tunable over a 58-nm window centered on 1053 nm.
ABSTRACT
An efficient, 10.4-GHz bulk phase modulator is demonstrated that produces frequency-modulated optical bandwidths in excess of 300 GHz in a double-pass configuration with modest microwave drive power. The waveguide resonator design employs velocity matching to maximize phase-modulation efficiency and a modified form of cutoff waveguide coupling to achieve a high microwave cavity Q factor that reduces power requirements. The measured microwave performance of the modulator agrees well with performance predicted from fully anisotropic, three-dimensional numerical simulations.
ABSTRACT
A phase-only spatial light modulator is used in conjunction with a spatial filter to provide independent control of the phase and amplitude of a laser beam. Continuous amplitude modulation of the beam is achieved with a resolution relevant to beam shaping of high-energy laser beams. Amplitude beam correction in a closed loop is demonstrated.
