Ship/Aircraft Communication and Tracking Using a 2-Micron Laser and a Membrane-Mirror Retroreflector

We propose to develop an optical line-of-sight communication and tracking link to enable secure voice and data transfer between aircraft and ship during landing approach. The system will be based on an existing compact, diode-pumped, Tm,Ho:YLF laser (mounted on the carrier) and a extremely compact modulatable retroreflector (mounted on the aircraft) which is constructed with membrane mirrors. The 2- micron laser has been developed for lidar applications, and produces up to 4.6 W of CW, TEM, power. The membrane mirrors are commercially available (manufactured by Optron Systems, Inc.) and can be modulated at rates of 1 MHz or more. Simultaneous ship-to-aircraft communication would be effected by modulating the CW laser electro- optically at tens of megahertz, whereas aircraft-to-ship communication would be accomplished by modulating the return signal with the retroreflector. The proposed system would acquire the retroreflected signal, perhaps using the modulation to enhance the signal, then switch to a communication mode while a quadrant detector/tracking system automatically maintains the laser pointing at the aircraft. The proposed Phase I effort consists of a feasibility study and the testing of a membrane mirror. A prototype system would be constructed and tested under a following Phase II.