A compact laser system with a folded annular resonator cavity defined by spherical mirrors (17, 18), enabling the generation of a multipass beam path between the mirrors, each beam pass inclined at a small angle to the axis between the mirrors to form a zig-zag path (28, 29) therebetween. A long optical path is achieved within a short physical structure. The optical resonator cavity is confined in the gap between two cylindrical coaxial electrodes (13, 14) receiving RF power to excite the lasing gas. Apertures (23) are provided in the main cavity mirrors (17, 18), with a high reflectivity end mirror (24) behind one aperture at one end and a partially reflective output coupler (25) at the other end. A channeled ceramic cylindrical element (15, 20) within the annular shaped gap between the two cylindrical electrodes confines the lasing gas to the channels (16).

An improved architecture for optical waveguides as used in a diode-pumped alkali laser system is provided by using micro-channel-etched silicon or other metal in place of the more usual sapphire.

A radio frequency, RF, slab laser comprising a live electrode (102) and a ground electrode (108) whose inwardly facing surfaces face each other to form a gap for forming a plasma discharge when the live electrode is supplied with a suitable RF drive signal. The electrodes are enclosed in a vacuum space by a vacuum housing (114) with an access aperture (116). The access aperture is sealed with a vacuum flange (70) that comprises an electrically insulating connector. A plurality of hollow conductors (62) are arranged to extend through the vacuum flange into the vacuum space and connect with the live electrode. The hollow conductors connect to the live electrode to supply it with its RF drive signal and also coolant fluid which is distributed through fluid circulation channels (80a, 80b). Coolant fluid is supplied to the live electrode through certain ones of the hollow conductors and taken out by others.

A tunable laser has a first mirror, a second mirror, a gain medium, and a directional coupler. The first mirror and the second mirror form an optical resonator. The gain medium and the directional coupler are, at least partially, in an optical path of the optical resonator. The first mirror and the second mirror comprise binary super gratings. Both the first mirror and the second mirror have high reflectivity. The directional coupler provides an output coupler for the tunable laser.

A laser resonator comprising a specially designed front mirror 32. The front mirror 32 together with a rear mirror form a resonator cavity. As well as having a resonator cavity reflective surface 42, the front mirror 32 also has an output coupling reflective surface 44 which forms a continuation of the resonator cavity reflective surface 42 and extends at an angle thereto so as to direct a beam laterally out of the cavity. The output coupling reflective surface 44 and the resonator cavity reflective surface 44 are joined by a “soft” rounded edge 40 of arcuate cross-section, this rounded transition suppressing diffraction ripples that would otherwise be generated if the edge were “hard”, i.e. sharp.

A laser device includes: a first mirror and a second mirror that cause resonance of a plurality of beams having different wavelengths from one another; a diffraction grating that causes the beams that are incident from the first mirror with directions of beam central axes being different from one another to travel to the second mirror while aligning the beam central axes with one another, and causes the beams that are incident from the second mirror with the beam central axes being aligned with one another to travel to the first mirror while causing the directions of the beam central axes to be different from one another; and a housing unit housing a laser medium that is a medium through which the beams traveling between the first mirror and the diffraction grating pass, and has a discrete gain spectrum in which a peak occurs at each wavelength of the beams.

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 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.

An improved dental laser system has been developed to cut enamel quickly and precisely, without detrimental residual energy, to provide a replacement for conventional high speed rotary burrs and commercially available dental laser systems.

A system and a method for generating tunable ultrafast optical pulses, the method comprising spectral broadening of a laser input beam by propagating the laser input beam in a nonlinear medium of a third-order nonlinear susceptibility χ.sup.(3), yielding an output laser spectrum; and one of: i) selecting at least one portion of the output laser spectrum, yielding an output pulse different than the input pulse and centered at a different frequency; ii) temporal compensation and spatial spreading of spectral components of the output laser spectrum; selecting two pulses at two different frequencies; and nonlinearly mixing the two pulses together in a first second-order nonlinear susceptibility χ.sup.(2) nonlinear crystal into a third pulse centered at a frequency which is a difference between the frequencies of the first two pulses; and iii) dividing output laser spectrum into a pump beam and a probe beam, directing a pump pulse to a third second-order nonlinear crystal for THz radiation generation; and directing a probe pulse to a third second-order nonlinear crystal for THz radiation reconstruction.