A gas laser device includes, in succession along an optical axis, a gas laser excited by a travelling wave, a convergent lens, two parallel-sided optical prisms adhering to one another in a symmetrical position in relation to the axis, and another convergent lens. The arrangement is such that two divergent elementary beams produced by the laser are brought together to have substantially less divergence.

The output power of any laser is optimized by providing an output mirror with a transmission which varies as a function of position on the mirror and transmitted wavelength. The transmission which corresponds to the optimum output for a given laser wavelength is chosen by monitoring laser output and moving the output mirror in at least one direction essentially perpendicular to the laser beam axis while maintaining the orientation of its reflecting surface perpendicular to the laser beam axis, and locating the mirror position corresponding to optimum laser output.

A method of and an apparatus for projecting an incident laser beam into a broad contact-type light amplifier. The laser beam is projected after the intensity distribution of the laser beam is made to coincide with the electromagnetic field distribution in the fundamental mode of the light amplifier. Since only the fundamental mode is used as the propagation mode of the light amplifier, a Gaussian beam amplified by the light amplifier is emitted. Consequently, the laser beam emitted from the light amplifier can be made into a several-micron spot by condensing the laser beam to a diffraction limit.

A source of laser energy of determinable, relatively narrow band spectral character, includes means for selectively changing the spectral character of the laser energy, preferably by filtering, so as to produce a desired very narrow-band spectral output. The laser energy is intercepted by means for both expanding it into a beam of desired dimension, and also collimating the beam; dispersing means positioned to receive the collimated beam causes the emerging laser energy to be dispersed at different angular dispositions as a function of the variation in its principal wavelength component. Means for focusing the laser energy at a selected image plane are provided whereby the selective changing of the spectral character of the beam and its principal wavelength component is determinative of the spatial disposition of the laser energy focused at the image plane. Thus, the position of the focused principal wavelength component may be changed to any one of a great number of possible positions by selectively changing the spectral character of the laser energy.

The problems of collimating, synchronizing and combining a plurality of laser beams to generate a composite beam are substantially reduced by the use of one or more lasers especially adapted to lase in two or more separate wavelengths. Specifically, a composite beam generating system comprises at least one multiwavelength laser for emitting a multiwavelength beam having at least two separated wavelength components, one or more additional lasers for generating respective additional beams, and means for combining the multiwavelength beam with one or more additional beams. In a preferred embodiment, a four-component multiwavelength composite beam is generated by polarization combination of the outputs of a pair of orthogonally polarized two-component multiwavelength lasers. The preferred embodiment of a multiwavelength laser is a liquid dye laser having, as one of the reflecting means defining the resonant cavity, an optical reflector having a reflectivity versus wavelength characteristic with a local minimum of reflectivity between two regions of substantially greater reflectivity.