Nonmechanical beam steering for passive sensors

Abstract

By using resets of multiple wavelengths to limit dispersion, we show conceptually that we will be able to steer passive, broadband, electro-optical sensors over wide angles using optical phased array technology. The dispersion associated with optical phased array beam steering can be limited to values of 20 to 80 times the diffraction limit for very large angle beam steering. Much of the remaining factor of 20 - 80 may be correctable using digital techniques. A significant obstacle associated with widespread implementation of optical phased array beam steering is wavelength dispersion associated with resets. We discuss optical phased array beam steering using resets of greater than one wavelength. By using larger resets the unfolded phase front for wavelengths other than the design wavelength can be maintained closer to a prism, thus limiting dispersion. This technique can be implemented with the variable period beam steering approach or the variable blaze beam steering approach. One way to implement the variable blaze beam steering approach is using moveable lenslets. This method of implementation is amenable to large value resets, so it is an attractive method of implementation for this multiple wavelength reset, limited dispersion, beam steering technique.