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.
CO/sub 2//H/sub 2/O gas sensor using a tunable Fabry-Perot filter with wide wavelength range
An electrostatically driven tunable MEMS Fabry-Perot filter (FPF) with wide wavelength range from 2.5 /spl mu/m to 4.5 /spl mu/m has been developed for non-dispersive infrared (NDIR) CO/sub 2//H/sub 2/O gas sensors. The electrostatic discharge (ESD) test and the long-term repetition-stability test were carried out for the FPF and no remarkable change of FPF performance was observed in either test. An NDIR system was equipped with the FPF, and the principle of the gas sensing method was confirmed. The resolutions defined by standard deviation are about 13 ppm for CO/sub 2/ of 2000 ppm and 0.35 g/m/sup 3/ for H/sub 2/O Of 22.5 g/m/sup 3/.
Long Ceramic Beam Tubes for Accelerator Magnets
The ceramic beam tubes for the fast and abort kickers and the bucker and pinger magnets used at Fermilab must meet a number of exacting requirements. The tubes must be long and sufficiently straight so as not to limit magnet design. They must have wall strength capable of withstanding the atmospheric and mechanical forces encountered during construction and operation. Vacuum tight ceramic to stainless steel transitions must be of reasonable cost; they must also withstand high temperature processing and remain vacuum tight to the 10/sup -9/ Torr range. To remove the possibility of static charge buildup each tube must have a surface coating of indium oxide applied to the inner wall. This thin coating is difficult to achieve and requires the most careful attention to detail. The methods used at Fermilab to achieve these goals are presented in this paper.