Programmable amplitude- and phase-modulated femtosecond laser pulses in the mid-infrared.

We present a scheme to produce programmable phase- and amplitude-modulated femtosecond laser pulses in the mid-infrared regime of 3-10mum by difference frequency mixing. The 80-fs signal output of an optical parametric amplifier is shaped with a liquid-crystal mask and mixed in an AgGaS(2) crystal with a temporally stretched idler pulse. Without changing the mechanical alignment, we produce programmable amplitude modulations and chirped pulses at lambda=3mum with energy as high has thas 1muJ . This scheme, further, allows the generation of controllable pulse sequences. The results are in good agreement with theoretical simulations.

Optical parametric amplification of a shaped white-light continuum.

Phase-locked two-color sub-40-fs double pulses in the visible are produced by noncollinear parametric amplification of white light tailored in a pulse shaper with a liquid-crystal mask. The carrier phase between the pulses is conserved during the amplification process and can be adjusted, as can the temporal separation and the center of wavelengths of the pulses.

Lensless imaging through phase-conjugated backscattering in SF(6).

A phase-conjugate mirror based on stimulated Brillouin scattering in gaseous SF(6) at 248 nm was used for pattern transfer. We measured the pressure dependence of backscattering efficiency of the Brillouin mirror, which approached 40% reflectivity and was limited by the onset of gas breakdown. Measurement of the image contrast ratio showed high statistical fluctuation due to the threshold behavior of Brillouin scattering.

Highly efficient, high-quality phase-conjugate reflection at 308 nm using stimulated Brillouin scattering.

We report efficient, diffraction-limited phase conjugation of a XeCl laser beam (308 nm) using stimulated Brillouin scattering. Reflectivities approaching 100% are obtained by focusing a XeCl laser (<0.15-cm(-1) linewidth) at 300 GW/cm(2) into heptane or ethanol.

Efficient tunable ultraviolet source based on stimulated Raman scattering of an excimer-pumped dye laser.

We report on the design and performance of a tunable ultraviolet source based on stimulated Raman scattering in compressed hydrogen. The 440-nm output of an excimer-pumped dye laser was employed as pump source. By lowering the gas temperature to 78 K, an improvement of ~70% was obtained in the efficiency of conversion to the seventh anti-Stokes order at 193 nm.