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.

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.

An external optical feedback element (108) for tuning an output beam of a gas laser (102) having multiple wavelengths includes a partially reflective optical element (108) positioned on a beam path of the output beam (106) outside of an internal optical cavity of the gas laser (102), and a stage (114) to support the optical element and adjust rotation, horizontal tilt angle, and vertical tilt angle of the optical element with respect to the beam path. The output beam (106) is partially reflected at the optical element (108) and fed back into the internal optical cavity of the gas laser (102), with the intensity varying for multiple wavelengths and adjusted by changing rotation, horizontal tilt angle and vertical tilt angle of the optical element. Thereby, a variable feedback of the output beam into the internal optical cavity of the gas laser is provided, which leads to a selective output wavelength of the gas laser, either at a single line or at multiple lines simultaneously. This setup may allow to control the wavelength of a commercial CO2 gas laser without a modification of the laser itself by adding a coupled cavity with a wavelength selective element like a grating to the given gas laser resonator.

A method generates laser pulses by varying a Q-factor in a resonator. The method includes generating the laser pulses by controlling an optical modulator with a control signal for switching over between a first operating state of the optical modulator for generating a first Q-factor in the resonator and a second operating state of the optical modulator for generating a second Q-factor in the resonator. The second Q-factor is different than the first Q-factor. In order to generate a sequence of the laser pulses in which first laser pulses alternate with second laser pulses different than the first laser pulses, the optical modulator is controlled differently in each case alternately with the control signal for generating a respective first laser pulse, of the first laser pulses, and a respective second laser pulse, of the second laser pulses.

A pulse stretching fiber oscillator (or laser cavity) may comprise a chirped fiber Bragg grating (CFBG) and an optical circulator arranged such that a first portion of a beam that is transmitted through the CFBG continues to propagate through the laser cavity while a second portion of the beam that is reflected from the CFBG is stretched and chirped by the CFBG and directed out of the laser cavity by the optical circulator. Accordingly, a configuration of the CFBG and the optical circulator in the laser cavity may enable pulse stretching contemporaneous with outcoupling, which may prevent deleterious nonlinear phase from accumulating prior to stretching.

Systems and methods for ring laser gyroscopes (RLGs) are provided. An RLG includes a traveling-wave resonator cavity with three or more mirrors and a gain medium positioned in the traveling-wave resonator cavity between two of the three or more mirrors. The gain medium is a solid-state gain medium or a nonlinear optical medium. The RLG further includes a first pump laser and a second pump laser to pump the gain medium in different directions and generate first and second lasing signals that traverse the traveling-wave resonator cavity in a opposite directions. The RLG further includes first and second photodetectors to measure levels of the first and second lasing signals. The RLG further includes at least one processor configured to adjust a power level of the first pump laser and/or a power level of the second pump laser based on the measured power levels of the first and second lasing signals.

Disclosed in the present invention is a semiconductor laser, which includes one or more semiconductor chips (1-1), a total length of a gain region (1-11A) of a light-emitting unit (1-11) of each of the semiconductor chips (1-1) in a slow axis direction being 1 mm˜10 cm; a laser resonant cavity configured to adjust semiconductor laser emitted by the light-emitting unit (1-11) to resonate in the slow axis direction, so that the size of the gain region (1-11A) of the light-emitting unit (1-11) in the slow axis direction matches a fundamental mode spot radius ω.sub.0; and a fast-axis collimating element (FAC) disposed in the laser resonant cavity and configured to collimate the laser emitted by the light-emitting unit (1-11) in a fast axis direction. The semiconductor laser according to an embodiment of the present invention can improve the high-power output capability of the gain region on the one hand, and improve the beam quality on the other hand, which can achieve a high beam quality output of M.sup.2<2.

A CO.sub.2 laser that generates laser-radiation in just one emission band of a CO.sub.2 gas-mixture has resonator mirrors that form an unstable resonator and at least one spectrally-selective element located on the optical axis of the resonator. The spectrally-selective element may be in the form of one or more protruding or recessed surfaces. Spectral-selectivity is enhanced by forming a stable resonator along the optical axis that includes the spectrally-selective element. The CO.sub.2 laser is tunable between emission bands by translating the spectrally-selective element along the optical axis.

A femtosecond pulse laser apparatus includes a pump light source configured to provide a pump light, a gain medium configured to obtain a gain of a laser light using the pump light, a first curved mirror and a second curved mirror, which are provided at both sides of the gain medium, an output mirror configured to transmit a portion of the laser light and reflect the other portion of the laser light to the gain medium, a mode locking portion configured to generate a femtosecond pulse of the laser light, and an acoustic wave generator configured to provide an acoustic wave into the gain medium so as to adjust self-phase modulation of the laser light.

An electro-optic modulator (EOM) for altering an optical path length of an optical field is described. The EOM comprises first and second Brewster-angle cut nonlinear crystals having a first and second optical axis. The optical axes are orientated relative to each other such that when an optical field propagates through the nonlinear crystals it experiences no overall deviation. The nonlinear crystals are also arranged to be opposite handed relative to the optical field. The EOM has the advantage that its optical losses are lower when compared with those EOMs known in the art. In addition, the EOM can be inserted into, or removed from, an optical system without any deviation being imparted onto the optical field. This reduces the levels of skill and effort required on the part of an operator. The described method and apparatus for mounting the nonlinear crystals also suppresses problematic piezo-electric resonances within the nonlinear crystals.