Abstract: A system for nonlinear frequency conversion includes an acousto-optic modulator for diffracting a portion of an input laser beam as a first-order beam and transmitting a non-diffracted portion of the input laser beam as a zeroth-order beam. The system also includes a nonlinear crystal arranged to receive and frequency convert each of the zeroth-order and first-order beams to generate two respective frequency-converted laser beams, whereby, when the acousto-optic modulator changes the average-power ratio between the zeroth-order and first-order beams, variations of the heat load in the nonlinear crystal are minimized. Either one of the two frequency-converted laser beams may be used as an output laser beam of the system, while the other one of the two frequency-converted laser beams serves to stabilize the heat load in the nonlinear crystal when the acousto-optic modulator is operated to change the average power in the output laser beam.

Abstract: A multipass laser amplifier includes a mirror, a mirror device, a gain crystal, and refractive or diffractive beam-steering element. The gain crystal is positioned on a longitudinal axis of the multipass laser amplifier between the mirror and the mirror device. The beam-steering element is positioned on the longitudinal axis between the gain crystal and the mirror device. The beam-steering element has no optical power and deflects a laser beam, by refraction or diffraction, for each of multiple passes of the laser beam between the first mirror and the mirror device, such that each pass goes through the gain crystal for amplification of the laser beam and goes through a different respective off-axis portion of the beam-steering element. The no optical power of the beam-steering element enables maintaining a large beam size in the gain crystal, thereby facilitating amplification to high average power.

Abstract: In pulsed-laser apparatus for filamentary cutting a glass-sheet, a laser-beam is focused by a plano-convex focusing lens into the glass-sheet through a first surface of the sheet to a point close to a second surface of the sheet. Pulses from the laser are delivered in repeated bursts. The laser-beam fills the clear-aperture of the lens such that uncorrected spherical aberration in the focusing lens causes radial modulation of the beam between the lens and the focus point. This provides that each burst of pulses generates a filament extending between the first and second surfaces of the sheet.