Phased-array optics is the technology of controlling the phase and amplitude of light waves transmitting, reflecting, or captured (received) by a two-dimensional surface using adjustable surface elements. An optical phased array (OPA) is the optical analog of a radio-wave

phased array In antenna theory, a phased array usually means an electronically scanned array, a computer-controlled array of antennas which creates a beam of radio waves that can be electronically steered to point in different directions without moving th ...

. By dynamically controlling the optical properties of a surface on a microscopic scale, it is possible to steer the direction of light beams (in an OPA transmitter), or the view direction of sensors (in an OPA receiver), without any moving parts. Phased-array beam steering is used for optical switching and multiplexing in

optoelectronic Optoelectronics (or optronics) is the study and application of electronic devices and systems that find, detect and control light, usually considered a sub-field of photonics. In this context, ''light'' often includes invisible forms of radiat ...

devices and for aiming

laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The ...

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 Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other applications. In principle, it ...

. Devices permitting detailed addressable phase control over two dimensions are a type of

spatial light modulator A spatial light modulator (SLM) is an object that imposes some form of spatially varying modulation on a beam of light. A simple example is an overhead projector Transparency (projection), transparency. Usually when the term SLM is used, it means ...

(SLM).

Transmitter

An optical phased-array transmitter includes a light source (laser), power splitters, phase shifters, and an array of radiating elements. The output light of the laser source is split into several branches using a power splitter tree. Each branch is then fed to a tunable phase shifter. The phase-shifted light is input to a radiating element (a nanophotonic antenna) that couples the light into free space. Light radiated by the elements is combined in the far-field and forms the far-field pattern of the array. By adjusting the relative phase shift between the elements, a beam can be formed and steered.

Receiver

In an optical phased-array receiver, the incident light (usually coherent light) on a surface is captured by a collection of nanophotonic antennas that are placed on a 1D or 2D array. The light received by each element is phase-shifted and amplitude-weighted on a chip. These signals are then added together in the optic or electronic domain to form a reception beam. By adjusting the phase shifts, the reception beam can be steered to different directions, and light incident from each direction is collected selectively.

Applications

nanotechnology Nanotechnology, also shortened to nanotech, is the use of matter on an atomic, molecular, and supramolecular scale for industrial purposes. The earliest, widespread description of nanotechnology referred to the particular technological goal ...

, 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 Invisibility is the state of an object that cannot be seen. An object in this state is said to be ''invisible'' (literally, "not visible"). The phenomenon is studied by physics and perceptual psychology. Since objects can be seen by light i ...

optical camouflage Active camouflage or adaptive camouflage is camouflage that adapts, often rapidly, to the surroundings of an object such as an animal or military vehicle. In theory, active camouflage could provide perfect concealment from visual detection. Activ ...

have also been suggested.

DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the A ...

's Excalibur program aims to provide realtime correction of

atmospheric turbulence An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A ...

for a laser weapon.

References

External links

Phased Array OpticsAnimation of beam steering using phased arrays on YouTube
{{DEFAULTSORT:Phased-Array Optics Optical devices Display technology Hypothetical technology Emerging technologies

Transmitter

Receiver

Applications

See also

References

External links