Abstract: Angles of inclination of the two wavelength selection elements arranged on an optical path of a laser beam source are varied to make a laser output variable. Light transmitting ranges of the two wavelength selection elements are coincided with each other so as to adjust the light wavelength bands, thereby the laser beam is narrowed without increasing its fineness.

Abstract: This invention is provided with a wavelength selecting means for uses in selectively receiving beam in compliance with each of a reference beam and a measured beam in order to simplify a correction or comparison of oscillating wavelengths in the laser device and further to improve a reliability and a controlling responsive speed.

Abstract: It is an object of the present invention to provide A laser device of long life. In the laser device, light source is housed in transparent cooling vessel, and the vessel is filled with a cooling liquid which is circulated. The electrodes of the light source project out of the cooling vessel. Reflectors are provided outside the cooling vessel. The electrodes and the reflectors are out of contact with the cooling liquid.It is another object of the present invention to stabilize laser oscillation. A light source is housed in a first transparent cooling vessel. The first cooling vessel is filled with a first cooling liquid. A laser medium is housed in a second transparent cooling vessel. The second cooling vessel is filled with a second cooling liquid. A heat insulation layer is provided between the first and the second cooling vessels so that the first and the second cooling liquids are thermally insulated from each other.

Abstract: A non-linear optical material is used to convert a solid state laser ray of light output of a first wavelength into light of a shorter wavelength. The light output of shorter wavelength is suitable for use as a light source for lithography. Wavelengths as short as those obtained by excimer laser devices can be achieved. When the light source is used in lithography, the degree of integration of ICs for the new generation of 16MDRAM can be achieved more safely and simply than possible with excimer lasers.