Optical phased array technology

TLDR

Optical phased arrays enable lightweight, affordable sensors with precise stabilization, random‑access pointing, multiple simultaneous beams, dynamic focus/defocus, and high optical power handling, and they steer or otherwise operate on an already formed beam. The paper presents system concepts that combine a passive acquisition sensor with a laser radar. The arrays impose a phase profile on a beam using lithographically patterned liquid‑crystal phase shifters that achieve full‑wave differential phase shifts with low voltages, and high‑efficiency large‑angle steering requires sub‑wavelength spacing, making 1‑D arrays practical, while orthogonal 1‑D arrays deflect beams in both dimensions. Fabricated 4 cm × 4 cm optical phased arrays have successfully steered green, red, 1.06 µm, and 10.6 µm radiation.

Abstract

Optical phased arrays represent an enabling new technology that makes possible simple affordable, lightweight, optical sensors offering very precise stabilization, random-access pointing programmable multiple simultaneous beams, a dynamic focus/defocus capability, and moderate to excellent optical power handling capability. These new arrays steer or otherwise operate on an already formed beam. A phase profile is imposed on an optical beam as it is either transmitted through or reflected from the phase shifter array. The imposed phase profile steers, focuses, fans out, or corrects phase aberrations on the beam. The array of optical phase shifters is realized through lithographic patterning of an electrical addressing network on the superstrate of a liquid crystal waveplate. Refractive index changes sufficiently large to realize full-wave differential phase shifts can be effected using low (<10 V) voltages applied to the liquid crystal phase plate electrodes. High efficiency large-angle steering with phased arrays requires phase shifter spacing on the order of a wavelength or less; consequently addressing issues make 1-D optical arrays much more practical than 2-D arrays. Orthogonal oriented 1-D phased arrays are used to deflect a beam in both dimensions. Optical phased arrays with apertures on the order of 4 cm by 4 cm have been fabricated for steering green, red, 1.06 /spl mu/m, and 10.6 /spl mu/m radiation. System concepts that include a passive acquisition sensor as well as a laser radar are presented.