An optical circulator is a three- or four-port

optical device Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultravio ...

designed such that

light Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400– ...

entering any port exits from the next. This means that if light enters port 1 it is emitted from port 2, but if some of the emitted light is reflected back to the circulator, it does not come out of port 1 but instead exits from port 3. This is analogous to the operation of an electronic

circulator In electrical engineering, a circulator is a passivity (engineering), passive, non-Reciprocity (electrical networks), reciprocal three- or four-port (circuit theory), port device that only allows a microwave or radio frequency, radio-frequency ...

. Fiber-optic circulators are used to separate optical signals that travel in opposite directions in an

optical fiber An optical fiber, or optical fibre, is a flexible glass or plastic fiber that can transmit light from one end to the other. Such fibers find wide usage in fiber-optic communications, where they permit transmission over longer distances and at ...

, for example to achieve bi-directional transmission over a single fiber. Because of their high isolation of the input and reflected optical powers and their low

insertion loss In telecommunications, insertion loss is the loss of signal power resulting from the insertion of a device in a transmission line or optical fiber and is usually expressed in decibels (dB). If the power transmitted to the load before insertio ...

, optical circulators are widely used in advanced

fiber-optic communications Fiber-optic communication is a form of optical communication for transmitting information from one place to another by sending pulses of infrared or visible light through an optical fiber. The light is a form of carrier wave that is modulated ...

and fiber-optic sensor applications. Optical circulators are ''non-reciprocal'' optics, which means that changes in the properties of light passing through the device are not reversed when the light passes through in the opposite direction. This can only happen when the symmetry of the system is broken, for example by an external

magnetic field A magnetic field (sometimes called B-field) is a physical field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular ...

. A Faraday rotator is another example of a non-reciprocal optical device, and indeed it is possible to construct an optical circulator based on a Faraday rotator.

History

In 1965, Ribbens reported an early form of optical circulator that utilized a

Nicol prism A Nicol prism is a type of polarizer. It is an optical device made from calcite crystal used to convert ordinary light into plane polarized light. It is made in such a way that it eliminates one of the rays by total internal reflection, i.e. ...

with a Faraday rotator. With the advent of

fiber Fiber (spelled fibre in British English; from ) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often inco ...

and guided-wave optics, waveguide-integrable and polarization-independent optical circulators were later introduced. The concept was later extended to silicon photonic waveguide systems. In 2016, Scheucher et al. have demonstrated a fiber-integrated optical circulator whose nonreciprocal behavior originated from the

chiral Chirality () is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek language, Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is dist ...

interaction between a single ⁸⁵Rb atom and the confined light in a

whispering-gallery mode Whispering-gallery waves, or whispering-gallery modes, are a type of wave that can travel around a concave surface. Originally discovered for sound waves in the whispering gallery of St Paul's Cathedral, they can exist for light and for other wa ...

microresonator. The routing direction of the device is controlled by the internal

quantum state In quantum physics, a quantum state is a mathematical entity that embodies the knowledge of a quantum system. Quantum mechanics specifies the construction, evolution, and measurement of a quantum state. The result is a prediction for the system ...

of the atom and the device is able to route

individual An individual is one that exists as a distinct entity. Individuality (or self-hood) is the state or quality of living as an individual; particularly (in the case of humans) as a person unique from other people and possessing one's own needs or g ...

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless particles that can ...

s. In 2013, Davoyan and Engheta proposed a nanoscale plasmonic Y-circulator based on three dielectric waveguides interconnected with a magneto-optical junction with plasmonic nanorods.

References

External links

US Patent 5,909,310 (USPTO)(Google Patents)
Optical components {{Optics-stub

History

See also

References

External links