Frequency Tunable Surface Acoustic Wave Actuators for Adjustable Pitch Diffraction Grating

• Published in: Journal of microelectromechanical systems 2020-10, Vol.29 (5), p.699-705
• Main Authors: Frez, Clifford F., Coskun, M. Bulut, Scott, Valerie J., Wu, Yen-Hung, Fraeman, Abigail, Rais-Zadeh, Mina
• Format: Article
• Language: English
• Subjects: Actuators; Delay lines; Diffraction; Diffraction efficiency; Diffraction grating; Diffraction gratings; Frequency ranges; Gratings; Gratings (spectra); imaging spectrometers; Instruments; Monochromators; Optical instruments; Optical surface waves; Pitch; Radio frequency; Spectrometers; Surface acoustic waves; Transducers; tunable surface acoustic wave; Wave diffraction; Wavelength division multiplexing
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2020.3000151

Diffraction gratings are commonly used in optical instruments such as in spectrometers, monochromators, and wavelength division multiplexing devices. The diffraction efficiency is directly related to the ratio of the grating spacing or pitch to the wavelength of the light. In a sinusoidal grating (or holographic grating) the efficiency is generally lower than a blazed grating with a saw tooth profile, but the spectral coverage can be broader. To address a large spectral range, advanced spectrometers use a number of diffraction gratings with a fixed pitch. In this paper, we show for the first time, the use of a tunable-frequency surface acoustic wave (SAW) delay line as a broad-band sinusoidal diffraction grating. To tune the frequency, we tune the effective spacing of the interdigitated transducers (IDTs) by applying specific phases to each IDT finger. The prototype SAW grating covers frequency range of 86 MHz to 360 MHz corresponding to optical range of 1.3~\mu \text{m} to 9~\mu \text{m} . [2020-0189]