The USAF Phillips Laboratory, solar research group at NSO/Sacramento Peak has designed a narrow-band tunable near infrared filter that uses two tunable Fabry Perot (FP) etalons and works between 1200 and 1700 nm with appropriate blockers. The FP Etalons and their controllers have been purchased from Queensgate. The order-sorting, broad-band FP has a FWHM pass band of 0.19 nm and a free spectral range (FSR) of 4.09 nm at 1565 nm. The narrow FP has a FWHM pass band of 171 mÅ and FSR about 0.548 nm, at 1565 nm. A high transmission prefilter is available for use between 1563 and 1566.5 nm. Initial tests of this filter system at the NSO/SP Vacuum Tower Telescope using a 128 × 128 InGaAs camera from Sensors Unlimited, the Michigan State 128 × 128 HgCdTe camera, and a specially constructed rotatable wave-plate and polarizer system, have demonstrated the capabilities of this system in making spectropolarimetric images in the spectral line FeI 1564.85 nm. Tests on the dual FP system at the VTT are in progress with the goal of evolving the system to a stand-alone vector magnetic field patrol instrument. The instrument and its components are available for use at the VTT on a shared risk basis. Additional information on this system can be obtained by contacting any of the following scientists.
Craig Gullixson, Steve Keil, K.S. Balasubramaniam