Large-aperture multiple quantum well modulating retroreflector for free-space optical data transfer on unmanned aerial vehicles

We describe progress in the development of a multiple quantum well modulati ng retroreflector, including a description of recent demonstrations of an i nfrared data link between a small rotary-wing unmanned airborne vehicle and a ground-based laser interrogator using the device designed and fabricated at the Naval Research Laboratory (NRL). Modulating retroreflector systems couple an optical retroreflector, such as a corner cube, and an electro-opt ic shutter to allow two-way optical communications using a laser, telescope , and pointer-tracker on only one platform. The NRL modulating retroreflect or uses a semiconductor-based multiple quantum well shutter capable of modu lation rates greater than 10 Mbps, depending on link characteristics. The t echnology enables the use of near-infrared frequencies, which is well known to provide covert communications immune to frequency allocation problems. This specific device has the added advantage of being compact, lightweight, covert, and requires very low paper. Up to an order of magnitude in onboar d power can be saved using a small array of these devices instead of the ra dio frequency equivalent. In the described demonstration, a Mbps optical li nk to an unmanned aerial vehicle in flight at a range of 100 to 200 feet is shown. Near real-time compressed video was also demonstrated at the Mbps l evel and is described. (C) 2001 Society of Photo-Optical Instrumentation En gineers.