Abstract: Provided is a cryostat that can effectively prevent water condensation on the surface of a cell. The cryostat includes: a casing having an inlet port and exit port; a cell housing provided in the casing; a temperature controller for adjusting the temperature of the cell; a first optical path tube for guiding a light beam from the inlet port of the casing to the cell housing; a second optical path tube for guiding the light beam having passed through the cell housing to the exit port of the casing; first and second optical windows disposed at openings, exposed to the outside, of the first and second optical path tubes, respectively; and sealing materials having a water vapor transmission rate of 30000 cc·cm2·mm·sec·cm Hg×1010 or lower, disposed at the peripheries of the first and second optical windows to seal the first and second optical path tubes.

Abstract: After a resist mask with a predetermined thickness profile is overlaid on a piezoelectric substrate, the substrate is shaped to an objective three-dimensional configuration by dry etching process using an etching gas with a differential etching rate between the piezoelectric substrate and the mask. The thickness profile may be given to the mask by reflow of masking material or by compression with a precision stamp. The substrates can be shaped to a three-dimensional configuration corresponding to an amplified thickness profile of the mask by compositional control of a reactive gas during dry etching. Since the piezoelectric material is accurately shaped to an objective form without defects, high-quality elements and devices are provided.