Scientific Solutions Inc. (SSI) has developed a tunable liquid crystal Fabry-Perot (LCFP) etalon system comprised of a resolving and a suppression etalon in tandem. The 30-micron resonant cavity spacing of the resolving etalon provides for high spectral resolution while the system maintains the significantly broader free spectral range of the 6-micron gap suppression etalon across the tunable region. An applied electric field alters the ordinary refractive index of nematic liquid crystal cells within each etalon cavity, thereby
altering the resonant properties of the etalons, allowing for system tunability over several orders of interference. This system acts as a tunable optical filter with an operating range from 700nm to 1100nm.
Testing of the LCFP etalon system with both a high resolution Czerny-Turner monochrometer and a stabilized ND:Yag laser demonstrate a FWHM of 0.67nm to 1.03nm. System transmission reaching 70% of polarized light is achieved with tunability over one free spectral range in approximately 30 milliseconds. The free spectral range of the tandem etalon system ranges from 27nm-36nm over the operating range, and
allows for 40 randomly selectable spectral channels per free spectral range. This system is designed for use in spectral imaging systems, initially for the semiconductor industry, but is equally applicable to the earth remote sensing community.
During the past four decades a variety of optical remote sensing techniques have revealed a rich spectrum of wave activity in the upper atmosphere. Many of these perturbations, with periodicites ranging from ~5 min to several hours and horizontal scales of a few ten's of km to several thousands km, are due to freely propagating buoyancy (or acoustic-gravity waves), and forced tidal oscillations. Optical observations of the spatial and temporal characteristics of these waves in the mesosphere and lower thermosphere (MLT) region (~80-100 km) are facilitated by several naturally occurring, vertically distinct nightglow layers. This paper describes the use of state-of-the-art ground-based CCD imaging techniques to detect these waves in intensity and temperature. All-sky (180°) image measurements from Bear Lake Observatory, Utah are used to illustrate the characteristics of small-scale, short period (< 1 hour) waves that are most frequently observed at MLT heights including a particular set of ducted wave motions, possibly associated with mesospheric bores. These results are then contrasted with measurements of mesospheric temperature made using a separate imaging system capable of determining induced temperature amplitudes of much larger-scale wave motions and investigating night-to-night and seasonal variability in mesospheric temperature.