Characteristics of crystallographic gratings.
We report the observation and characterization of a resonance effect in gratings fabricated on GaAs substrates by use of a crystallographically preferential wet chemical etch that terminates at the (111) family of planes. Also, we demonstrate an in situ etch-monitoring study of the diffraction characteristics of these gratings. The light intensity in the first order of diffraction was monitored in Littrow reflection during etching at 632.8- and 543.5-mm wavelengths. Scanning-electron microscopy was performed on several samples to correlate the etch depth with diffraction efficiency. The variation of diffraction intensity with depth showed a narrow peak at a shallower grating depth and a broader peak at a larger grating depth. These diffraction characteristics are explained on the basis of a competitive interaction between the resonance effect of the incident optical mode and the magnitude of the first Fourier component of the grating profile that primarily couples the incident and diffracted optical modes.
Sarathy
J
J
Diaz
D C
DC
Hartin
O L
OL
Campbell
J C
JC