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: Apparatus for generating ultraviolet (UV) pulsed laser-radiation for material-processing includes a laser-source providing infrared (IR) pulsed laser-radiation and a frequency-conversion module. A lithium tetraborate (Li2B4O7) crystal located within the frequency-conversion module converts the IR pulsed laser-radiation to UV pulsed laser-radiation by non-linear harmonic generation. The frequency-conversion module is an airtight enclosure that may be evacuated or contain a dry gas. A flexible optical fiber-assembly transports the IR pulsed laser-radiation from the laser-source to the frequency-conversion module.

Abstract: Apparatus for generating ultraviolet (UV) pulsed laser-radiation for material-processing includes a laser-source providing infrared (IR) pulsed laser-radiation and a frequency-conversion module. A lithium tetraborate (Li2B4O7) crystal located within the frequency-conversion module converts the IR pulsed laser-radiation to UV pulsed laser-radiation by non-linear harmonic generation. The frequency-conversion module is an airtight enclosure that may be evacuated or contain a dry gas. A flexible optical fiber-assembly transports the IR pulsed laser-radiation from the laser-source to the frequency-conversion module.

Abstract: A solid-state MOPA includes a mode-locked laser delivering a train of pulses. The pulses are input to a fast E-O shutter, including polarization-rotating elements, polarizing beam-splitters, and a Pockels cell that can be driven alternatively by high voltage (HV) pulses of fixed long and short durations. A multi-pass amplifier follows the E-O shutter. The E-O shutter selects every Nth pulse from the input train and delivers the selected pulses to the multi-pass amplifier. The multi-pass amplifier returns amplified seed-pulses to the E-O shutter. The shutter rejects or transmits the amplified pulses depending on whether the HV-pulse duration is respectively short or long. Transmitted amplified pulses are delivered to a transient amplifier configured for separately suppressing first-pulse over-amplification and residual pulse leakage.

Abstract: A solid-state MOPA includes a mode-locked laser delivering a train of pulses. The pulses are input to a fast E-O shutter, including polarization-rotating elements, polarizing beam-splitters, and a Pockels cell that can be driven alternatively by high voltage (HV) pulses of fixed long and short durations. A multi-pass amplifier follows the E-O shutter. The E-O shutter selects every Nth pulse from the input train and delivers the selected pulses to the multi-pass amplifier. The multi-pass amplifier returns amplified seed-pulses to the E-O shutter. The shutter rejects or transmits the amplified pulses depending on whether the HV-pulse duration is respectively short or long. Transmitted amplified pulses are delivered to a transient amplifier configured for separately suppressing first-pulse over-amplification and residual pulse leakage.

Abstract: An optically pumped laser oscillator or amplifier includes a laser head having a gain medium exhibiting polarization-dependent absorption along two crystallographic axes and a pump source producing a pump beam. The medium's absorption coefficients along both said crystallographic axes are equal or the difference between the absorption coefficients relative to the lowest absorption coefficients R=Abs(?c??a)/(min(?c, ?a)) is reduced at least by a factor of two compared to the same relative difference between the two absorption coefficients at the medium's absorption peaks, used for conventional pumping by pumping with unpolarized or partially polarized pump light at a wavelength around which the average absorption coefficients along both of said crystallographic axes are equal or present a relative difference that is reduced by a factor of two or better compared to conventional pumping around the medium's absorption peaks.

Abstract: An optically pumped laser oscillator or amplifier includes a laser head having a gain medium exhibiting polarization-dependent absorption along two crystallographic axes and a pump source producing a pump beam. The medium's absorption coefficients along both said crystallographic axes are equal or the difference between the absorption coefficients relative to the lowest absorption coefficients R=Abs(?c-?a)/(min(?c, ?a)) is reduced at least by a factor of two compared to the same relative difference between the two absorption coefficients at the medium's absorption peaks, used for conventional pumping by pumping with unpolarized or partially polarized pump light at a wavelength around which the average absorption coefficients along both of said crystal-lographic axes are equal or present a relative difference that is reduced by a factor of two or better compared to conventional pumping around the medium's absorption peaks.

Abstract: An optically pumped laser oscillator or amplifier including a laser head including a gain medium exhibiting polarization-dependent absorption along two crystallographic axes and a pump source producing a pump beam. The medium's absorption coefficients along both of the crystallographic axes are equal or the difference between the absorption coefficients relative to the lowest absorption coefficients is reduced at least by a factor of two compared to the same relative difference between the two absorption coefficients at the medium's absorption peaks. In some embodiments, the gain medium is a crystal, e.g., a Neodymium-doped Vanadate (Nd:YVO4) crystal, greater than 15 mm. In various embodiments, the optically pumped laser oscillator or amplifier includes two pump sources producing two pump beams.

Abstract: Driver for Pockels cells and using this Pockels cell within laser systems The driver i.e. the electrical control of the Pockels cell is modified from the standardly known H-configuration using the switches S1, S2A; S1A, S2 A by adding at least one more switch (S2B; S1B; S2B). This switch can either replace the usually used recharging resistors (R2) or can be placed to these in parallel. It is also possible to use an arrangement using 4 switches (S1A, S2A, S1B, S2B) and no recharging resistors at all. Using such a driver with a Pockels cell pulses can be selected in laser systems more efficiently. Pulse sequences with well defined widths and spacing can be produced for certain application.

Abstract: A device for the optical excitation of laser-active crystals with a diode laser (1) is disclosed. The diode laser (1) generates pump radiation (2), and the laser-active crystal (14) is arranged in a solid-state laser or solid-state laser amplifier. The laser-active crystal (14) has an axis (C) with strong absorption and an axis (A) with weak absorption. The pump radiation (2) from the diode laser (1) is substantially polarised linearly in a privileged polarisation direction. The device is configured in such a way that the pump radiation (2) is injected into the laser-active crystal (14) with a polarisation direction which is oriented parallel to the weak-absorption axis (A). The polarisation of the pump radiation in the vicinity of the laser-active crystal is oriented parallel relative to the weak-absorption axis.

Abstract: A device for the optical excitation of laser-active crystals with a diode laser (1) is disclosed. The diode laser (1) generates pump radiation (2), and the laser-active crystal (14) is arranged in a solid-state laser or solid-state laser amplifier. The laser-active crystal (14) has an axis (C) with strong absorption and an axis (A) with weak absorption. The pump radiation (2) from the diode laser (1) is substantially polarised linearly in a privileged polarisation direction. The device is configured in such a way that the pump radiation (2) is injected into the laser-active crystal (14) with a polarisation direction which is oriented parallel to the weak-absorption axis (A). The polarisation of the pump radiation in the vicinity of the laser-active crystal is oriented parallel relative to the weak-absorption axis.

Abstract: An optically pumped laser oscillator or amplified, comprising: a laser head including a gain medium exhibiting polarization-dependent absorption along two crystallographic axes; a pump source producing a pump beam wherein the medium's absorption coefficients along both said crystallographic axes are equal or the difference between the absorption coefficients relative to the lowest absorption coefficients R=Abs(&agr;c−&agr;a)/(min(&agr;c,&agr;a)) is reduced at least by a factor of two compared to the same relative difference between the two absorption coefficients at the medium's absorption peaks, used for conventional pumping either by pumping with unpolarized or partially polarized pump light at a wavelength around which the average absorption coefficients along both of said crystallographic axes are equal or present a relative difference that is reduced by a factor of two or better compared to conventional pumping around the medium's absorption peaks or by pumping with a combination of two pump

Abstract: The driver i.e. the electrical control of the Pockels cell is modified from the standardly known H- configuration using the switches S1, S2A; S1A, S2A by adding at least one more switch (S2B; S1B, S2B). This switch can either replace the usually used recharging resistors (R2) or can be placed to these in parallel. It is also possible to use an arrangement using 4 switches (S1A, S2A, S1B, S2B) and no recharging resistors at all. Using such a driver with a Pockels cell pulses can be selected in laser systems more efficiently. Pulse sequences with well defined widths and spacing can be produced for certain applications.