SBIR-STTR Award

Ultra-high rejection optical filters for operation at the following three wavelengths, 589-nm, and 678-nm are to be investigated. These wavelengths are selected because they are the laser beacon wavelengths for existing adaptive optical filters hat offer a rejection of 10-6, with a high throughput, wide field-of-view and the fast gating that are also required for the adaptive optics application. We will design, build, and deliver 589-nm FADOF that has a field-of-view of 5-o, a peak throughput f 70%, and a background rejection of >10-5. We will identify concepts for building ultra-high rejection, high throughput optical filters at 510.6-nm and 678.2-nm. We will identify potential practical filter concepts for the Cu vapor laser lines, develop a simple theory to predict the filter performance, and estimate the filter operating conditions. The results of this portion of the effort will be the design parameters for a Cu vapor laser line filter. In Phase II, the devices that have been conceptually designed in Phase I will be hardware designed, built, and tested.

We will build a high transmission, ultra-high rejection optical filters for Cu laser line that will provide sufficient skylight suppression so that the adaptive optical system can be operated during the daytime. In addition, we will also implement a gating system on the filter. The gating is desirable for two reasons: first, the beacon signal is sensed only over a small "range gate" in the atmosphere so isolating the range gate is accomplished only be turning the filter on for a short time and, second, it is possible to only turn the filter on after the laser beam leaves the telescope so that the light scattered by the telescope optics as the pulsed laser beam leaves the telescope does not saturate the wavefront sensor. To be useful for this application the time gating must operate at 5 kHz repetition rate and have real-times of about tens of ns. The filter is expected to have a throughput of greater than 80%, a solar background rejection of 10 to the sixth power, and a wide field-of-view. In addition, the filter will preserve optical image information and hence can be used in imaging applications.