An optical device including an acousto-optic modulator (AOM), a laser, an upstream optical fibre extending between the laser and the AOM, a downstream optical fibre located downstream of the AOM and a reflector connected to the fibre downstream of the AOM. The optical device including the upstream fibre is a polarisation-maintaining optical fibre, and/or the downstream fibre is arranged so that a transit time of the optical beam through said downstream fibre from the AOM to the reflecting means is nonzero and shorter than or equal to half an open duration of the AOM, and/or the AOM includes a crystal in which the entrance/exit faces are planar and are at a nonzero angle to each other, and/or at least one of the two entrance/exit faces is at a nonzero angle to a direction of propagation of the acoustic wave in the crystal.

A laser apparatus includes a laser oscillator; an acousto-optic modulation unit including a first acousto-optic modulator that diffracts a laser beam from the laser oscillator when a first ultrasonic wave is applied and a second acousto-optic modulator that diffracts a higher order beam output from the first acousto-optic modulator when a second ultrasonic wave is applied; and an amplifier that amplifies the laser beam from the acousto-optic modulation unit, a propagation direction of the first ultrasonic wave relative to a diffracted direction of the higher order beam emitted from the first acousto-optic modulator and a propagation direction of the second ultrasonic wave relative to a diffracted direction of a higher order beam emitted from the second acousto-optic modulator being different.

A fiber optic assembly includes: a gain fiber configured to output signal light; a first taper configured to expand the signal light output by the gain fiber; and a reversing prism configured to receive counter-pumping light and output the counter-pumping light into the first taper. The first taper is further configured to direct the counter-pumping light towards the gain fiber.

A system includes a laser source operable to provide a laser beam, a laser amplifier having a gain medium operable to provide energy to the laser beam when the laser beam passes through the laser amplifier, and a residual gain monitor operable to provide a probe beam and operable to derive a residual gain of the laser amplifier from the probe beam when the probe beam passes through the laser amplifier while being offset from the laser beam in time or in path.

A solid state laser apparatus includes a plurality of cold heads, a cooling apparatus, laser media and a seed light source. The cooling apparatus is configured to cool the plurality of cold heads. The laser media are arranged in contact with each of the plurality of cold heads, and configured to amplify a first laser beam and reflect the first laser beam. The seed light source is configured to irradiate a first laser medium of the laser media with the first laser beam. The first laser medium is arranged on a first of the cold heads. The laser media are configured to reflect the first laser beam irradiated to the first laser medium to a second laser medium of the laser media. The second laser medium is arranged on a second of the cold heads. The cold heads are configured to cool the laser media.

An optical system element includes a first enclosure designed for receiving in circulation a functional fluid and at least one inlet and/or outlet window located on the first enclosure and through which a light beam can pass. The inlet and/or outlet window includes two viewports which delimit a spacer cavity adjacent to the first enclosure. The spacer cavity is designed to receive a second fluid with a predetermined optical index and is equipped with a device for adjusting the pressure therein. Degradation of a beam during its passage through the inlet and/or outlet window can be limited by careful selection of the optical index of the second fluid and the pressure in the spacer cavity.

A laser system may include a seed laser formed from a Ti:Sapphire laser providing pulsed light and an optical parametric amplifier to generate pulsed light within a Holmium emission spectrum as seed pulses in response to the pulsed light from the Ti:Sapphire laser. A laser system may further include an amplifier to generate amplified pulses of light in response to the seed pulses from the seed laser, where the amplified pulses include at least some of the seed pulses amplified by the one or more Holmium-doped gain media pumped by the one or more pump lasers. The amplifier may include one or more Holmium-doped gain media and one or more pump lasers providing continuous-wave pump light within an absorption spectrum of the one or more Holmium-doped gain media.

A laser light-source apparatus includes a seed light source 10, fiber amplifiers 20 and 30 and a solid state amplifier 50 configured to amplify pulse light output from the seed light source, nonlinear optical elements 60 and 70 configured to perform wavelength conversion on the pulse light output from the solid state amplifier 50 and output the resultant pulse light, a semiconductor optical amplifier 15 disposed between the seed light source 10 and the solid state amplifier 50 and configured to amplify the pulse light output from the seed light source 10, and a control unit 100 configured to execute gain switching control processing in which the seed light source 10 is driven at a desired pulse rate, and semiconductor optical amplifier control processing in which an injection current to the semiconductor optical amplifier 15 is controlled depending on the pulse rate of the seed light source 10, and thus, generation of a giant pulse can be reliably prevented, regardless of the pulse rate of the seed light source.

A set of optical elements for optical extraction composed of packed expanding optical cross sections to efficiently extract from a large gain region. The elements are rectangular shaped concave small expansion lenses matched to rectangular convex collimating lenses. Absorbing sheets divide an overall large volume up into smaller volumes to minimize losses due to amplified spontaneous emission. This arrangement has various applications, particularly in inertial confinement technology, where it may be used to extract energy from KrF laser media energized by electron beams. For certain applications, this regime of the gain medium may have zones at the absorbing sheets where this is no gain.

An apparatus includes: abeam splitter on abeam path, the beam splitter configured to receive light from a deep ultraviolet (DUV) light source; and a first plurality of reflective optical elements on the beam path. The beam splitter is configured to direct a portion of the light received from the DUV light source toward the first plurality of reflective optical elements; the first plurality of reflective optical elements is configured to rotate a divergence of the portion of the light to produce rotated light; and the beam splitter is configured to direct the rotated light and a portion of the light received from the DUV light source onto an output beam path.