A carbon dioxide gas-discharge slab-laser is assembled in a laser-housing. The laser-housing is formed from a hollow extrusion. An interior surface of the extrusion provides a ground electrode of the laser. Another live electrode is located within the extrusion, electrically insulated from and parallel to the ground electrode, forming a discharge-gap of the slab-laser. The electrodes are spaced apart by parallel ceramic strips. Neither the extrusion, nor the live electrode, include fluid coolant channels. The laser-housing is cooled by fluid-cooled plates attached to the outside thereof.

A fiber laser apparatus includes: amplification optical fibers including first and second amplification optical fibers, each of which having different amplification characteristics and including a core to which an active element is doped; one or more cooling plates having a first cooling surface that thermally contacts and cools the first amplification optical fiber and a second cooling surface that thermally contacts and cools the second amplification optical fiber; one or more module boxes including a gain module box that houses the amplification optical fibers and the one or more cooling plates; and an enclosure housing the one or module boxes. The first and second cooling surfaces are disposed at different heights in the gain module box. At least a portion of the first cooling surface overlaps at least a portion of the second cooling surface as viewed along a height direction.

Apparatus and methods for producing ultrashort optical pulses are described. A high-power, solid-state, passively mode-locked laser can be manufactured in a compact module that can be incorporated into a portable instrument. The mode-locked laser can produce sub-50-ps optical pulses at a repetition rates between 200 MHz and 50 MHz, rates suitable for massively parallel data-acquisition. The optical pulses can be used to generate a reference clock signal for synchronizing data-acquisition and signal-processing electronics of the portable instrument.

An arrangement monitors an optical element. The arrangement includes: a light source configured to emit radiation onto a surface of the optical element; a detector configured to detect the radiation that has been at least partially reflected at the surface of the optical element; and a holder for the optical element, in which the light source and the detector are integrated. The holder has a cooling region through which a cooling liquid is configured to flow, the cooling region being in contact with the optical element. The holder has a reservoir, through which a beam path between the light source and the detector extends. The reservoir is configured to receive the cooling liquid leaking out at the optical element in case of a leakage.

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 surgical laser system includes a pump module configured to produce pump energy within an operating wavelength, a gain medium configured to convert the pump energy into first laser energy, a non-linear crystal (NLC) configured to convert a portion of the first laser energy into second laser energy, which is a harmonic of the first laser energy, an output, and a first path diversion assembly having first and second operating modes. When the first path diversion assembly is in the first operating mode, the first laser energy is directed along the output path to the output, and the second laser energy is diverted from the output path and the output. When the first path diversion assembly is in the second operating mode, the second laser energy is directed along the output path to the output, and the first laser energy is diverted from the output path and the output.

An arrangement monitors an optical element. The arrangement includes: a light source configured to emit radiation onto a surface of the optical element; a detector configured to detect the radiation that has been at least partially reflected at the surface of the optical element; and a holder for the optical element, in which the light source and the detector are integrated. The holder has a cooling region through which a cooling liquid is configured to flow, the cooling region being in contact with the optical element. The holder has a reservoir, through which a beam path between the light source and the detector extends. The reservoir is configured to receive the cooling liquid leaking out at the optical element in case of a leakage.

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 cooling system for a laser includes: a laser, a housing of the laser having a water inlet and a water outlet; an air cooling mechanism including a first pipeline, an air cooling module, a cooling liquid tank, and a water pump; wherein the air cooling module, the cooling liquid tank, and the water pump are sequentially connected through the first pipeline, both ends of the first pipeline is connected to the water inlet and the water outlet, respectively; the water pump is closer to the water inlet; a water cooling mechanism including a second pipeline and a water chiller in communication with the second pipeline, both ends of the second pipeline being connected to the water inlet and the water outlet, respectively; and a solenoid valve with one inlet and two outlets arranged at a junction of the water outlet, the first pipeline, and the second pipeline.