A modified Seya–Namioka monochromator with improved light intensity transfer

A monochromator with improved focusing properties has been designed and constructed using a novel optical geometry based on the Seya–Namioka concept. The only optical elements used are a spherical grating and a cylindrical mirror mounted in the exit arm within the Rowland circle , retaining the Seya–Namioka scanning simplicity while minimizing reflections. This optical system compensates for the astigmatism associated with spherical optics at large incidence angles as in the Seya–Namioka geometry shortening the effective vertical focal length and providing a single, tight focus. A method of constructing a similar apparatus for any given spherical grating is presented. Experiments involving coherent vacuum ultraviolet generation from harmonic mixing demonstrate the utility of the new design. © 2000 American Institute of Physics. S0034-6748 00 05510-6