Apparatus for providing optical radiation (15), which apparatus comprises an optical input (13), a coupler (2), a first semiconductor amplifier (3), a controller (4), a preamplifier (61), a power amplifier (62) and an output fibre (5), wherein: the optical input (13) is for receiving input optical radiation (14); the optical input (13) is connected in series to the coupler (2), the first semiconductor amplifier (3), the preamplifier (61), the power amplifier (62), and the output fibre (5); the apparatus being characterized in that: the first semiconductor amplifier (3) comprises a waveguide (6) having a low reflecting facet (8); the first semiconductor amplifier (3) is in a double pass configuration such that the low reflecting facet (8) is connected to both the optical input (13) and the preamplifier (61) via the coupler (2); and the controller (4) is configured to cause the waveguide (6) of the first semiconductor amplifier (3) to operate in saturation thereby enabling the first semiconductor amplifier (3) to reduce non-linear effects in the preamplifier (61), the power amplifier (62), and the output fibre (5).

A laser resonator includes a pair of optical elements forming a first optical path having a focused beam waist, one or more mirrors forming a second optical path of approximately parallel light connected to the first optical path, and a laser medium arranged in the second optical path. Induced emission light generated from the laser medium reciprocates or circles in a path formed by the first optical path and the second optical path. A distance between the pair of optical elements is adjustable, and a beam diameter at the second optical path is adjusted by adjusting the distance between the pair of optical elements.

A radio-frequency, RF, slab laser 10 with a Z-fold resonator cavity defined by an output mirror 32, a first fold mirror 34, a second fold mirror 36 and a rear mirror 30. The second fold mirror 36 is rotated by an adjustment angle away from the angle it would have if the mirrors were all plane mirrors and directed the round trip beam path by direct reflection. Moreover, the rear mirror 30 is rotated by an adjustment angle that is approximately twice the adjustment angle of the second fold mirror 36. These rotations of the rear mirror 30 and second fold mirror 36 suppresses parasitic mode paths that would otherwise exist.

A laser apparatus according to the present disclosure includes an excitation light source configured to output excitation light, a laser crystal disposed on an optical path of the excitation light, a first monitor device disposed on an optical path of transmitted excitation light after having transmitted through the laser crystal to monitor the transmitted excitation light, a temperature adjustment device configured to adjust a temperature of the excitation light source to a constant temperature based on a temperature command value, and a controller configured to change the temperature command value based on a result of monitoring by the first monitor device.

A method for operating a laser device, including providing a laser pulse in a resonator so that the laser pulse circulates in the resonator, the laser pulse having a carrier wave; determining an offset frequency (f.sub.0) of the frequency comb corresponding to the laser pulse, the frequency comb having a plurality of laser modes (f.sub.m) at a distance (f.sub.rep) from one another, the frequencies of which can be described by the formula: f.sub.m=m*f.sub.rep+f.sub.0, m being a natural number, and varying the offset frequency (f.sub.0) by varying a geometric phase () that is imparted to the carrier wave of the laser pulse per resonator circulation.

A waveguide gas laser having a laser resonator cavity of a variable length is subjected to cyclical varying of the length of the cavity during generation of a laser beam a length variation amount sufficient to force a laser beam generated in the resonator cavity though a substantially complete optical longitudinal cavity mode at a rate operable to smooth at least one laser beam parameter variation. In this manner variation in the laser beam parameter is averaged by moving through at least a portion of an optical longitudinal cavity mode.

A laser device for laser resonance ionization includes a wavelength variable grating-type titanium-doped sapphire laser and includes a titanium (Ti) doped titanium sapphire crystal disposed within a resonator. The titanium sapphire crystal is fixedly disposed on a stage. The titanium-doped sapphire crystal can be moved in the optical axis direction by the stage, thereby changing the position of the titanium-doped sapphire crystal. The switching between the wideband mode and the high-output mode can be performed by changing the position of the titanium-doped sapphire crystal.

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.

A frequency-doubled laser, including: a first reflecting mirror, a second reflecting mirror, a gain medium, a telescope module, a polarizing element, and a nonlinear crystal; the first reflecting mirror and the second reflecting mirror are spaced apart to form a resonator of the frequency-doubled laser; the polarizing element, the gain medium, the telescope module, and the nonlinear crystal are located in the resonator, and the telescope module is located between the gain medium and the nonlinear crystal. The present disclosure further provides a method of generating harmonic laser. The frequency-doubled laser and the method of generating harmonic laser make the position of nonlinear crystal more flexible, and the possibility of damage to the nonlinear crystal is reduced.

A pulse laser apparatus (100) for creating laser pulses (1), in particular soliton laser pulses (1), based on Kerr lens mode locking of a circulating light field in an oscillator cavity (10), comprises at least two resonator mirrors (11, 12, . . . ) spanning a resonator beam path (2) of the oscillator cavity (10), at least one Kerr-medium (21, 22, 23) for introducing self-phase modulation and self-focusing to the circulating light field in the oscillator cavity (10), at least one gain-medium (31) for amplifying the circulating light field in the oscillator cavity (10), and a tuning device (40) for setting a first mode-locking condition and a second mode-locking condition of the oscillator cavity (10) such that an intra-cavity threshold-power for mode-locking at the first mode-locking condition is lower than that at the second mode-locking condition, wherein the first mode-locking condition is adapted for starting or shutting-down of the Kerr lens mode locking and the second mode-locking condition is adapted for continuous Kerr lens mode locking and a resonator-internal peak-power of the circulating light field is higher at the second mode-locking condition than at the first mode-locking condition. Furthermore, a method of operating a pulse laser apparatus is described.