Phased array optics (PAO) is the technology of controlling the phase of light waves transmitting or reflecting from a two-dimensional surface by means of adjustable surface elements. It is the optical analogue of phased array radar. By dynamically controlling the optical properties of a surface on a microscopic scale, it is possible to steer the direction of light beams, or the view direction of sensors, without any moving parts. Hardware associated with beam steering applications is commonly called an optical phased array (OPA). Phased array beam steering is used for optical switching and multiplexing in optoelectronic devices, and for aiming laser beams on a macroscopic scale.
Complicated patterns of phase variation can be used to produce diffractive optical elements, such as dynamic virtual lenses, for beam focusing or splitting in addition to aiming. Dynamic phase variation can also produce real-time holograms. Devices permitting detailed addressable phase control over two dimensions are a type of spatial light modulator (SLM).
In nanotechnology, phased array optics refers to arrays of lasers or SLMs with addressable phase and amplitude elements smaller than a wavelength of light. While still theoretical, such high resolution arrays would permit extremely realistic three-dimensional image display by dynamic holography with no unwanted orders of diffraction. Applications for weapons, space communications, and invisibility by optical camouflage have also been suggested.
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