Project Title:

Photoelectrochemical Fabrication of Spectroscopic Diffraction Gratings

08.01-9450
Photoelectrochemical Fabrication of Spectroscopic Diffraction Gratings
Eic Laboratories, Inc.
111 Downey Street
Norwood
MA
02062
Rauh
David R.
29279
50,000
GSFC

Abstract:

Photoelectrochemical etching is a one step, maskless process for producing diffraction
and transmission gratings in hard inorganic optical materials.  The substrate material
must be a semiconductor and the etching light source must be of energy greater than
its bandgap.  The grating pattern is projected onto the substrate immersed in a mild
etching electrolyte, and it is etched in relief preferentially in areas of illumination
to a depth proportional to illumination intensity and exposure time.  In principle,
the process has molecular level resolution, and shallow interference gratings have
been photoelectrochemically etched with periods exceeding 6000 grooves/mm.

	Phase I entails demonstration of efficient gratings in Si and ZnSe optically polished
crystals.  Three kinds of groove profiles will be considered:  sinusoidal, produced
holographically; laminar (used in x-ray spectroscopy) and sawtooth (used in Eschelles)
by projection imaging.  Effects of etchant composition, external electrical bias,
total exposure, crystalline orientation and surface preparation on grating morphology
and optical efficiency will be examined.