Laser Beam Steering with Semiconductor Waveguide

The ability to rapidly and randomly steer a laser beam is critical to the success of free-space satellite-based laser radar systems for missile defense and target tracking. By applying waveguide technology, Spire win demonstrate multi-dimensional, all-electronic laser beam steering. Parallel arrays of electronically phase-modulated waveguide structures are being fabricated, and a metal grating has been designed to spatially dissect an incident coherent planar waveform, emitted at 1059 nm by a NdYAG laser. The rotation of the output light-beam will occur through constructive interference effects in the far field. A two dimensional array of phase-control channels would allow scanning the beam over the entire image plane. Initial efforts in Phase I are being focused on fabrication and testing of a two channel, vertically situated set of buried waveguides. The implementation of a double- buried semiconductor structure with two GaAs cores and AlxGa1-xAs cladding has been analyzed in detail to determine materials parameters that would allow us to demonstrate the highly novel concept of high speed, electronic laser steering of a laser beam in the vertical direction. The GaAs waveguide is being grown to contain a pn junction, while the cladding consists of Al0.08Ga0.92 As, with the lower cladding doped n-type, and the upper cladding doped p-type. For a 2 micron thick waveguide, only the fundamental mode and perhaps the first harmonic can be supported, which should allow demonstration of optical interference in the far field.