Far-field evanescent wave propagation using coupled subwavelength gratings for a MEMS sensor

摘要

A technique was developed to couple near-field evanescent waves into observable diffraction orders in the far-field region. This investigation was of two gratings that have a 1.0 (mu)m grating period in glass and 1.1 (mu)m in silicon and are individually subwavelength, but when coupled together yield an 11.0 (mu)m effective grating period. This effective grating period is not subwavelength to a 1.550 (mu)m infrared incident source and exhibits higher diffraction orders. Optimum evanescent wave coupling efficiency was simulated by varying the grating thickness and the grating separation between the subwavelength gratings. This proposed evanescent wave coupling concept is being investigated for use in a bulk silicon MEMS accelerometer.