Highly efficient second-harmonic generation of ultraintense Nd:glass laser pulses

Three-wave mixing mediated femtosecond pulse compression in β-barium borate

Nonlinear pulse compression mediated by three-wave mixing is demonstrated for ultrashort Ti:sapphire pulses in a type II phase-matched β-barium borate (BBO) crystal using noncollinear geometry. 170 μJ pulses at 800 nm with a pulse duration of 74 fs are compressed at their sum frequency to 32 fs with 55 μJ of pulse energy. Experiments and computer simulations demonstrate the potential of sum-frequency pulse compression to match the group velocities of the interacting waves to crystals that were initially not considered in the context of nonlinear pulse compression.

Ultrahigh contrast from a frequency-doubled chirped-pulse-amplification beamline

This paper describes frequency-doubled operation of a high-energy chirped-pulse-amplification beamline. Efficient type-I second-harmonic generation was achieved using a 3 mm thick 320 mm aperture KDP crystal. Shots were fired at a range of energies achieving more than 100 J in a subpicosecond, 527 nm laser pulse with a power contrast of 10(14).

Simple and sensitive technique for alignment of the pinhole of a spatial filter of a high-energy, high-power laser system

In this paper, a new method for alignment of the pinhole of a spatial filter (SF) has been proposed and demonstrated experimentally. The effect of the misalignment of the pinhole on the laser beam profiles has been calculated for circular and elliptical Gaussian laser beams. Theoretical computation has been carried out to illustrate the effect of an intensity mask, placed before the focusing lens of the SF, on the spatial beam profile after the pinhole of the SF. It is shown, both theoretically and experimentally, that a simple intensity mask, consisting of a black dot, can be used to visually align the pinhole with a high accuracy of 5% of the pinhole diameter. The accuracy may be further improved using a computer-based image processing algorithm. Finally, the proposed technique has been demonstrated to align a vacuum SF of a compact 40 J Nd:phosphate glass laser system.

Energy transfer from wide-band supercontinuum to narrow-band second harmonic generation

We present an experimental and theoretical study of energy transfer from a wide-band supercontinuum to narrow-band second harmonic light during propagation of a femtosecond pulse in a MgO:LiNbO(3) crystal. The energy removed from the supercontinuum at 1038 nm by phase-matched second harmonic generation is compensated by energy transfer from other wavelengths within the supercontinuum by self phase modulation via the Kerr effect.

High-efficiency second-harmonic generation of superintense ultrashort laser pulses

The effect of instantaneous cubic nonlinearity on second-harmonic generation of femtosecond laser pulses is investigated. The possibility of improving generation efficiency and shortening pulse duration is analyzed. Energy conversion efficiency of 60% was obtained in an experiment in a 1 mm thickness KDP crystal at the peak intensity of 0.6 TW/cm(2) and the duration of 60 fs.

Asymmetric spectral broadening and temporal evolution of cross-phase-modulated third harmonic pulses

The influence of cross-phase modulation on third-harmonic generation is theoretically studied. Generalized phase-matching conditions for third-harmonic generation including pump-intensity-dependent phase shifts related to self- and cross-phase modulation effects are discussed. The phase mismatch between the pump and third-harmonic pulses is shown to vary from the leading edge of the pump pulse to its trailing edge, resulting in an asymmetric spectral broadening of the third harmonic.

Second-harmonic generation and wave-front correction of a terawatt laser system

By combining second-harmonic generation and wave-front correction of a hybrid Ti:sapphire-Nd:glass terawatt laser chain, we were able to generate a focused intensity above 10(19) W/cm(2), with an estimated 10(9):1 intensity contrast ratio. The frequency of the laser is doubled by use of a type I KDP crystal, and wave-front correction is achieved with a deformable mirror coupled to a wave-front sensor.

Three-wave interaction solitons in optical parametric amplification

This paper applies three-wave interaction (TWI)-soliton theory to optical parametric amplification when the signal, idler, and pump wave can all contain TWI solitons. We use an analogy between two different velocity regimes to compare the theory with output from an experimental synchronously pumped optical parametric amplifier. The theory explains the observed inability to compress the intermediate group-velocity wave and 20-fold pulse compression in this experiment. The theory and supporting numerics show that one can effectively control the shape and energy of the optical pulses by shifting the TWI solitons in the pulses.

Determination of the optical-axis orientation of a uniaxial crystal by frequency-domain interferometry

Frequency-domain interferometry has been used to find the optical axis of a uniaxial, birefringent crystal. The dependence of the interference fringe spacing on the incident angle and the direction of the optical axis were determined in a 4.6-cm-thick KDP crystal.

Second-harmonic generation under phase-velocity and group-velocity mismatch:influence of cascading self-phase and cross-phase modulation

Temporal and spectral characteristics of pulses resulting from second-harmonic generation of 120-fs amplified Ti:sapphire laser pulses up to 0.1 mJ at a wavelength of 815 nm in type I KDP crystal were experimentally and theoretically analyzed. Widely different behaviors were observed, according to the sign of the phase mismatch. Comparison between the theoretical simulation and experimental data demonstrates that the competition between third- and second-order nonlinear phenomena strongly modifies the structure of the pulses generated.

Second-harmonic pulse compression in the soliton regime

Analytical soliton solutions of the three-wave interaction equations are shown to exhibit high power conversion for a range of nonlinear materials with no satellite peaks and energy conversion close to 100%. Related numerical solutions that yield power conversion up to 10 times those of the initial waves with less than 3% energy in the small satellite peaks and high-energy efficiency are exhibited for KDP crystals; substantial compression of the fundamental pulses is observed in this case.

Generation of compressed 600-720-nm tunable femtosecond pulses by transient frequency mixing in a beta-barium borate crystal

We demonstrate the feasibility of the compression of tunable pulses by means of sum-frequency generation under special group-velocity mismatch conditions. beta-Barium borate crystal has been shown to support the upconversion process, resulting in 160-fs pulses tunable within 600-720 nm when mixing 1.3-ps 1055-nm pulses from a Nd:glass laser with 0.95-ps pulses tunable within 1400-2200 nm from a traveling-wave parametric generator. A similar compression of ~150-fs Ti:sapphire pulses predicted for the sum-frequency tuning range of 520-590 nm.