Compact Solid Etalon Computational Spectrometer: FY19 Optical Systems Technology Line-Supported Program

The Compact Solid Etalon Computational Spectrometer line program is developing fabrication techniques for wedged low reflectivity etalons and algorithms enabling a novel hyperspectral imaging architecture based on a solid low finesse etalon paired with a traditional imager. The hyperspectral imager can be designed to operate for any spectral band with the selection of an appropriate imager and etalon substrate material. The architecture is a high throughput design for use in low light applications and can operation in single shot or scanning modes. The spectral performance can be both high spectral resolution and large spectral bandwidth in volumes no larger than the imager themselves. This offers significant volume reduction, up to 1 to 2 orders of magnitude, over traditional high resolution spectral devices. This is achieved by utilizing the advances and cost reduction of large high pixel count imagers essentially sacrificing spatial resolution in one axis and/or collection time for increases in spectral performance. In order to offer the highest performance spectral imager, solid etalons are necessary compared to alternative air-gap wedged etalons which have been previously investigated. From the program onset, it was decided that pursuit of solid etalons is the key enabling component of this architecture and therefore prioritized. Initial modeling efforts determined the design requirements of wedged etalons targeting two important spectral bands. The first was a hybrid two material etalon for use in the visible to short wavelength infrared (VNIR/SWIR), 0.42.4 micrometer, spectral band. The second was a single material etalon for use in the long wavelength infrared (LWIR), 7.512 micrometer, spectral band. The etalon design requirements for these spectral bands will be discussed. Finally, an overview of the etalon fabrication development will be provided.