Large-aperture Fabry-Perot filters based on silicon/silicon carbonitride distributed Bragg reflectors for the near-infrared
This contribution presents silicon carbonitride as a new low refractive index material for integration together with silicon in suspended distributed Bragg reflector membranes. We show how its benign mechanical stress properties can be used to fabricate inherently flat mirror membranes of up to 5 mm diameter. Due to the large refractive index contrast to silicon such mirror membranes exhibit high reflectance over a wide spectral range. Using these mirrors, we demonstrate a proof of concept for a large aperture Fabry-Perot filter with narrow bandwidth that could help miniaturize hyperspectral imaging sensors.
MEMS Fabry–Pérot Interferometers With Double Membrane Mirrors for Improved Mirror Parallelism
This paper presents surface micromachined MEMS Fabry–Pérot interferometers (FPIs) with two released membrane mirrors. Fabrication of such FPIs with large-area membrane reflectors of up to 5 mm in diameter for first-order operation in the near infrared is shown. The mirrors are distributed Bragg reflectors based on silicon and silicon carbonitride. Single mirror membrane FPIs with the same mirror design are used as a benchmark in order to demonstrate the improvements achievable by the double membrane approach. To that end, the FPIs are characterized with respect to their top surface flatness by white light interferometry as well as to the variations of the optical gap width over the aperture area by spatially resolved transmittance measurements. It is shown that the upper mirror membranes are flat within the nanometer range for both approaches. Nevertheless, single membrane FPIs exhibit strongly increasing gap variations for increasing membrane diameters due to a bow in the substrate wafer, thus decreasing the filter resolution over the full aperture. On the other hand, for double-membrane FPIs, the mirrors are highly parallel with a standard deviation of the gap as low as 2 nm. [2018-0096]
Crossing Borders: Time, Memory, and the Construction of Identity in Song of the Exile
This article analyzes the construction of memory in Ann Hui's Song of the Exile as it intersects with issues of cultural identity, national allegory, and women's autobiographies.