Spectral-temporal measurement capabilities of third-order correlators.

We present a method extending scanning third-order correlator temporal pulse evolution measurement capabilities of high power short pulse lasers to spectral sensitivity within the spectral range exploited by typical chirped pulse amplification systems. Modelling of the spectral response achieved by angle tuning of the third harmonic generating crystal is applied and experimentally validated. Exemplary measurements of spectrally resolved pulse contrast of a Petawatt laser frontend illustrate the importance of full bandwidth coverage for the interpretation of relativistic laser target interaction in particular for the case of solid targets.

Enhanced ion acceleration from transparency-driven foils demonstrated at two ultraintense laser facilities.

Laser-driven ion sources are a rapidly developing technology producing high energy, high peak current beams. Their suitability for applications, such as compact medical accelerators, motivates development of robust acceleration schemes using widely available repetitive ultraintense femtosecond lasers. These applications not only require high beam energy, but also place demanding requirements on the source stability and controllability.

Laser-driven multi-MeV high-purity proton acceleration via anisotropic ambipolar expansion of micron-scale hydrogen clusters.

Multi-MeV high-purity proton acceleration by using a hydrogen cluster target irradiated with repetitive, relativistic intensity laser pulses has been demonstrated. Statistical analysis of hundreds of data sets highlights the existence of markedly high energy protons produced from the laser-irradiated clusters with micron-scale diameters. The spatial distribution of the accelerated protons is found to be anisotropic, where the higher energy protons are preferentially accelerated along the laser propagation direction due to the relativistic effect.

Highly stable sub-nanosecond Nd:YAG pump laser for optically synchronized optical parametric chirped-pulse amplification.

We developed an optically synchronized highly stable frequency-doubled Nd:YAG laser with sub-nanosecond pulse duration. The 1064 nm seed pulses generated by soliton self-frequency shift in a photonic crystal fiber from Ti:sapphire oscillator pulses were stabilized by controlling input pulse polarization. The seed pulses were amplified to 200 mJ by diode-pumped amplifiers with a high stability of only <0.

Discriminative detection of laser-accelerated multi-MeV carbon ions utilizing solid state nuclear track detectors.

A new diagnosis method for the discriminative detection of laser-accelerated multi-MeV carbon ions from background oxygen ions utilizing solid-state nuclear track detectors (SSNTDs) is proposed. The idea is to combine two kinds of SSNTDs having different track registration sensitivities: Bisphenol A polycarbonate detects carbon and the heavier ions, and polyethylene terephthalate detects oxygen and the heavier ions. The method is calibrated with mono-energetic carbon and oxygen ion beams from the heavy ion accelerator.

High-contrast high-intensity repetitive petawatt laser.

We report the generation of 63 J of broadband pulse energies at 0.1 Hz from the J-KAREN-P laser, which is based on an OPCPA/Ti:sapphire hybrid architecture. Pulse compression down to 30 fs indicates a peak power of over 1 PW.

Approaching the diffraction-limited, bandwidth-limited Petawatt.

J-KAREN-P is a high-power laser facility aiming at the highest beam quality and irradiance for performing state-of-the art experiments at the frontier of modern science. Here we approached the physical limits of the beam quality: diffraction limit of the focal spot and bandwidth limit of the pulse shape, removing the chromatic aberration, angular chirp, wavefront and spectral phase distortions. We performed accurate measurements of the spot and peak fluence after an f/1.

Simple synchronization technique of a mode-locked laser for Laser-Compton scattering γ-ray source.

We propose a simple and effective synchronization technique between a reference electrical oscillator and a mode-locked laser for a narrowband picosecond Laser-Compton scattering γ-ray source by using a commercial-based 1-chip frequency synthesizer, which is widely used in radio communication. The mode-locked laser has been successfully synchronized in time with a jitter of 180 fs RMS for 10 Hz-100 kHz bandwidth. A good stability of 640 μHz at 80 MHz repetition rate for 10 h operation has also been confirmed.

Temporal contrast enhancement of petawatt-class laser pulses.

We demonstrate the temporal contrast enhancement in a petawatt-class Ti:sapphire chirped-pulse amplification (CPA) laser system. An extra saturable absorber, introduced downstream after a low-gain optical parametric chirped-pulse amplification (OPCPA) preamplifier, has improved the temporal contrast in the system to 1.4×10(12) on the subnanosecond time scale at 70 TW power level.

Proton acceleration to 40 MeV using a high intensity, high contrast optical parametric chirped-pulse amplification/Ti:sapphire hybrid laser system.

Using a high-contrast (10(10):1) and high-intensity (10(21) W/cm(2)) laser pulse with the duration of 40 fs from an optical parametric chirped-pulse amplification/Ti:sapphire laser, a 40 MeV proton bunch is obtained, which is a record for laser pulse with energy less than 10 J. The efficiency for generation of protons with kinetic energy above 15 MeV is 0.1%.

Efficient generation of Xe K-shell x rays by high-contrast interaction with submicrometer clusters.

The interaction between a 25 TW laser and Xe clusters at a peak intensity of 1 × 10¹⁹ W/cm² has been investigated. Xe K-shell x rays, whose energies are approximately 30 keV, were clearly observed with a hard x-ray CCD at 3.4 MPa.

Laser ceramic materials for subpicosecond solid-state lasers using Nd3+-doped mixed scandium garnets.

We have successfully developed and demonstrated broadband emission Nd-doped mixed scandium garnets based on laser ceramic technology. The inhomogeneous broadening of Nd(3+) fluorescence lines results in a bandwidth above 5 nm that is significantly broader than that for Nd:YAG and enables subpicosecond mode-locked pulse durations. We have also found the emission cross section of 7.

High temporal and spatial quality petawatt-class Ti:sapphire chirped-pulse amplification laser system.

Optical parametric chirped-pulse amplification (OPCPA) operation with low gain by seeding with high-energy, clean pulses is shown to significantly improve the contrast to better than 10(-10) to 10(-11) in a high-intensity Ti:sapphire laser system that is based on chirped-pulse amplification. In addition to the high-contrast broadband, high-energy output from the final amplifier is achieved with a flat-topped spatial profile of filling factor near 77%. This is the result of pump beam spatial profile homogenization with diffractive optical elements.

High-spatiotemporal-quality petawatt-class laser system.

We have developed a femtosecond high-intensity laser system that combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric CPA (OPCPA) techniques and produces more than 30 J broadband output energy, indicating the potential for achieving peak powers in excess of 500 TW. With a cleaned high-energy seeded OPCPA preamplifier as a front end in the system, for the compressed pulse without pumping the final amplifier, we found that the temporal contrast in this system exceeds 10(10) on the subnanosecond time scales, and is near 10(12) on the nanosecond time scale prior to the peak of the main femtosecond pulse. Using diffractive optical elements for beam homogenization of a 100 J level high-energy Nd:glass green pump laser in a Ti:sapphire final amplifier, we have successfully generated broadband high-energy output with a near-perfect top-hat-like intensity distribution.

High-contrast, high-intensity laser pulse generation using a nonlinear preamplifier in a Ti:sapphire laser system.

We report a high-contrast, high-intensity Ti:sapphire chirped-pulse amplification system that incorporates a nonlinear preamplifier based on optical parametric chirped-pulse amplification (OPCPA). By cooling the Ti:sapphire crystal in the final amplifier down to 77 K, the chirped-pulses are amplified to 2.9 J at a 10 Hz repetition rate without a thermal lensing effect.

High-energy, high-contrast, multiterawatt laser pulses by optical parametric chirped-pulse amplification.

We describe a compact, reliable, high-power, and high-contrast noncollinear optical parametric chirped-pulse amplifier system. With a broadband Ti:sapphire oscillator and grating-based stretching and compression, the chirped pulses are amplified from 0.1 nJ to 122 mJ in type I beta-barium borate optical parametric chirped-pulse amplifiers with a total gain of over 10(9) at 10 Hz repetition rate.

Prepulse-free, multi-terawatt, sub-30-fs laser system.

We have built a prepulse-free, multi-terawatt, ultrashort pulse laser system, which combines both conventional laser amplification and optical parametric chirped pulse amplification (OPCPA) techniques. By employing an OPCPA system after the regenerative amplifier in a Ti:sapphire chirped pulse amplification laser chain, we have dramatically enhanced the prepulse contrast by 6 orders of magnitude. A prepulse contrast of better than 4.

360-W average power operation with a single-stage diode-pumped Nd:YAG amplifier at a 1-kHz repetition rate.

We report a high-average-power laser-diode-pumped Nd:YAG master oscillator power amplifier system that has a minimum number of elements in the single multipass zigzag-slab amplifier stage and is used to pump a high-peak-power and high-average-power Ti:sapphire laser system. This phase-conjugated system produces an average power of 362 W at 1 kHz in a 30-ns pulse with an optical-to-optical conversion efficiency of 14%. With an external KTP doubler this system generates 132 W of green average output power at 1 kHz with a conversion efficiency of 60% when pumped at a power level of 222 W.

High energy second-harmonic generation of Nd:glass laser radiation with large aperture CsLiB6O10 crystals.

We have demonstrated the generation of a high-energy green laser pulse using large aperture CsLiB6O10 (CLBO) crystals for the first time to our knowledge. A pulsed energy of 25 J at 532-nm was generated using the 1064-nm incident Nd:glass laser radiation with an energy of 34 J. High conversion efficiency of 74 % at intensities of only 370 MW/cm2 was obtained using a two-stage crystal architecture.