Abstract: A laser light, whose wavelength is to be measured, is introduced into an etalon, a concentric circular interference stripe derived from the etalon is irradiated onto a one-dimensional photodetector array and a diameter of the interference stripe is measured to measure the wavelength of the laser light. Alternatively, if a reference laser light of known wavelength is introduced into the etalon, as described above, a wavelength measurement of extremely high accuracy can be made without being affected by positional deviations of the optical system.

Abstract: A discharge exciting excimer laser device comprises a pair of main discharge electrodes, a dielectric and an auxiliary electrode. The dielectric is in a cylindrical form and has a side opposed to one of the main discharge electrodes, which side is formed into a flat plate-like portion. The auxiliary electrode is embraced within the dielectric leaving a space and is opposed to one of the main discharge electrodes with the flat plate-like portion of the dielectric sandwiched therebetween. Such a construction increases laser output and improves insulating performance.

Abstract: A gas laser apparatus having transparent laser windows provided on a laser chamber body, in which operating gases is sealed if necessary, comprising circulation means connected to the laser chamber body through an intake port and a discharge port for circulating gases within the laser chamber body and filtration means disposed in said circulation means, further comprising cutoff means for preventing the laser windows from being stained and open and closeably cutting off between the laser chamber body and the laser windows, and having a construction wherein in replacing the laser window, the cutoff means is once placed in a cutoff state, and the laser window is separated from the laser chamber body to place the laser window.