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 (radio), antenna theory, a phased array usually means an electronically scanned array, a computer-controlled Antenna array, array of antennas which creates a radio beam, beam of radio waves that can be electronically steered to point ...

. 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 radia ...

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'' originated as an acronym for light amplification by stimulated emission of radi ...

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 A spatial light modulator (SLM) is a device that can control the intensity, phase, or polarization of light in a spatially varying manner. A simple example is an overhead projector transparency. Usually when the term SLM is used, it means that ...

(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 is the manipulation of matter with at least one dimension sized from 1 to 100 nanometers (nm). At this scale, commonly known as the nanoscale, surface area and quantum mechanical effects become important in describing propertie ...

, 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 fr ...

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. Acti ...

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 Adva ...

's Excalibur program aims to provide realtime correction of

atmospheric turbulence In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to laminar flow, which occurs when a fluid flows in parallel layers with no disruption between t ...

for a laser weapon. The

Breakthrough Starshot Breakthrough Starshot is a research and engineering project by the Breakthrough Initiatives to develop a proof-of-concept fleet of light sail interstellar probes named ''Starchip'', to be capable of making the journey to the Alpha Centauri st ...

organisation has proposed to use phased arrays to precisely aim and steer propulsion lasers for a hypothetical gram-scale

solar sail Solar sails (also known as lightsails, light sails, and photon sails) are a method of spacecraft propulsion using radiation pressure exerted by sunlight on large surfaces. A number of spaceflight missions to test solar propulsion and navigati ...

-based craft or fleet of crafts.

References

External links

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

Transmitter

Receiver

Applications

See also

References

External links