Photonic Semiconductor Devices 355

absorbed

Taken in by a substance. Light is absorbed into a dark surface with little or no reflection.

absorption

The act or process of suppressing light rays. Absorption can cause signal loss in an optical fiber.

analog

A continuously variable signal. Analog signals differ from digital signals in that small fluctuations in the analog signal are meaningful.

anode

A positive electrode.

attenuation

The loss or decrease of signal power. Fiber optic cables have low attenuation compared to copper cables.

avalanche photodiode

A highly light-sensitive type of photodiode.

bandwidth

The amount of information or data that can be sent over a communications channel in a given period of time. The higher a channel's bandwidth, the more information it can carry.

bandwidth

The carrying capacity of a channel. Bandwidth determines how fast data flows through a cable.

bending

The act or process of changing the direction of light as it passes from one medium to another. Bending can cause signal loss in an optical fiber.

cathode

A negative electrode.

cladding

The protective layer surrounding the core of an optical fiber. The cladding protects the core from contaminants, supports the optical fiber, and reduces loss of light from the core.

copper cable

Electric power cables made from twisted pair copper wire.

core

The center part of an optical fiber through which light is transmitted.

crystal

A solid material with atoms arranged in a highly organized and repeating structure.

dark current

The small amount of current that flows through a photonic semiconductor device when it is not operating. Also known as leakage current.

dielectric

The stored electrical charge of an object. Dielectric materials conduct no electricity.

diffused light

A light ray that is reflected from a surface and broken up and scattered into different directions.

digital

Consisting of information that is input or output electronically as a series of pulses or signals either "on" or "off," often resulting in binary strings of 0s and 1s.

diode

A semiconductor device that acts as a one-way valve for electrical current.

discrete

A signal that has two states: ON and OFF.

dual inline package

A type of semiconductor packaging with two rows of external connecting terminals. Also known as a DIP.

electrical noise

An AC power line disturbance caused by sudden changes in the load. Electrical noise is problematic to solid state devices because they cannot differentiate between an intended electrical pulse and an unintended electrical spike.

electroluminescence

A process in which excited electrons emit light. LEDs work through electroluminescence.

electromagnetic energy

Energy from a magnetic field that is produced by the motion of electric charges such as electric current.

electromagnetic interference

Electrical noise in a circuit that can interrupt or degrade the performance of the circuit. Fiber optic cables are resistant to electromagnetic interference.

electron

A negatively charged particle that orbits the nucleus of an atom. Electrons play an integral role in conducting current.

fiber optic cable

A group of individual optical fibers bundled together. Fiber optic cables have higher bandwidth than standard copper cable.

fiber optic receiver

A device that amplifies the signal from a transmitter and converts it back into an electrical signal.

fiber optic transmitter

A photonic device that converts electrical signals into light signals. The transmitter sends a pulse of light through an optical fiber to the receiver, where it is converted back into an electrical signal.

fiber optics

A technology that transmits light rather than electricity through a fiber made of thin, flexible glass or plastic. Fiber optic cables are replacing older copper cables for most telecommunications applications.

forward-biased

A bias that causes electrons to flow in one direction only. Bias causes an electrical device to operate in a predetermined manner.

high impedance amplifier

An amplifier that increases the sensitivity of the receiver.

hole

An extra opening in P-type semiconductor material that is available for permitting movement of valence electrons. Holes play an integral role in conducting current.

infrared emitting diode

An LED that emits a wavelength of light below red in the color spectrum. Infrared light is not visible to the human eye.

integrated circuit

A complete electronic circuit. Its name resulted from the integration of previously separate transistors, resistors and capacitors, all on a single chip.

interface circuit

A circuit that converts the line voltages between the transmitter and the receiver.

jacket

The protective outer layer surrounding the cladding of an optical fiber. The jacket protects the optical fiber from physical damage.

LASCR

A light-driven semiconductor device that prevents current flow in either direction until it receives a signal. Also known as a light activated SCR.

laser diode

A semiconductor device that converts energy into light. Laser diodes have less attenuation than LEDs and use less power.

LCD

Liquid crystal display. A light-driven display device made from nematic liquid sealed between two pieces of polarized glass.

leakage current

The small amount of current that flows through a photonic semiconductor device when it is not operating. Also known as dark current.

LED

Light emitting diode. A semiconductor device that emits a narrow spectrum of light in a forward direction.

light emitting diode

A semiconductor device that emits a narrow spectrum of light in a forward direction. Also known as LED.

light-activated SCR

A light-driven semiconductor device that prevents current flow in either direction until it receives a signal. Also known as an LASCR.

light-dependent resistor

A type of resistor that decreases in resistance when it is exposed to light. Also known as a photoresistor and a photoconductor.

liquid crystal display

A light-driven display device made from nematic liquid sealed between two pieces of polarized glass.

medium

A carrier. Air and water are examples of media because they can carry an electrical charge.

millisecond

One thousandth of a second.

nanosecond

One billionth of a second.

near-infrared light

A wavelength below red but above infrared in the color spectrum. Near infrared light can be seen by the human eye.

nematic liquid

A substance that is composed of crystals that have the characteristics of both a solid and a liquid. Nematic liquid is used in LCDs.

optical amplifier

A device that increases the power of an optical signal without any conversion of the light into an electrical signal.

optical fiber

A filament made of thin, flexible glass or plastic through which light is transmitted. Optical fibers are bundled into groups to form fiber optic cable.

optical isolator

A solid state component that uses a light-emitting diode to transmit light through an optically transparent barrier between two isolated circuits. This barrier insulates circuits by allowing light to pass through, but not current.

optical source

The source of light. The optical source in a fiber optic transmitter is usually an LED or a laser diode.

optocoupler

A solid state component that uses a light-emitting diode to transmit light through an optically transparent barrier between two isolated circuits. This barrier insulates circuits by allowing light to pass through, but not current.

package

A protective cover designed to contain or support a semiconductor device.

photocell

A type of resistor that decreases in resistance when it is exposed to light. Also known as photoresistor, light-dependent resistor, and photoconductor.

photoconductor

A type of resistor that decreases in resistance when it is exposed to light. Also known as a photoresistor and a light-dependent resistor.

photodetector

A device that senses light. In fiber optic receivers, a photodetector is usually a PIN photodiode or an avalanche diode.

photodiode

A light-activated semiconductor device that allows current to flow in only one direction.

photon

A particle of light energy.

photonic semiconductor

A semiconductor device that uses light in order to create energy. Photonic semiconductors are an integral part of communications and networking technology.

photoresistor

A type of resistor that decreases in resistance when it is exposed to light. Also known as a light-dependent resistor and a photoconductor.

phototransistor

A semiconductor device that is highly sensitive to light. Photonic transistors are used in switching and amplifying applications, and they can conduct current in either direction.

phototriac

A semiconductor device that uses light to allow small control voltages and currents to switch very high voltages.

photovoltaic cell

A small conductive device that can produce an electric current when light shines on the cell.

PIN photodiode

A light-sensitive diode that conducts current in one direction only. PIN photodiodes have a fast response time.

pixel

An abbreviation for Picture Element. A tiny block of color.

PN junction

The part of a semiconductor device where P-type and N-type materials are located next to each other. The PN junction controls resistance.

polarized glass

A type of glass that filters out certain types of light waves. Polarized glass is used on LCD screens.

postamplifier

An amplifer in a fiber optic receiver that increases the detector's electrical signal to the level required for further signal processing.

preamplifier

An amplifer in a fiber optic receiver that prepares electronic signals for processing by the postamplifier.

PV array

A group of photovoltaic cells. PV arrays are used in solar-electric energy systems such as the electrical systems of satellites.

ray

A particle of light. Light is made up of rays and waves.

receiver

A device that detects and converts signals. Optical fibers are used with receivers to form fiber optic receivers.

reflected light

A light ray that bounces off a reflective surface at the exact angle at which it contacted the surface.

refracted light

A light ray that is bent into a different direction when it changes speed passing from one medium into another.

resistor

A device that controls current by opposing the passage of current.

reverse bias

A bias in which heightened resistance prevents current from flowing. Bias causes an electrical device to operate in a predetermined manner.

scattering

The act or process of reflecting light rays from an object, breaking them up and dispersing the rays into different directions. Scattering can cause signal loss in an optical fiber.

semiconductor

A solid state device, typically made of silicon, that is less conductive than a conductor, but more conductive than an insulator.

source drive circuit

A circuit that improves power conversion efficiency.

splicing

The act or process of creating a physical connection betweeen two separate pieces of optical fiber. Optical fibers should only be spliced by a technician who possesses the required skills and interconnection technology.

stimulated emission

The creation of additional photons from a single photon. Optical amplifiers use stimulated emission to increase the power of an optical signal.

telecommunications

The process of transmitting information to a receiver by means of electric current or pulses of light.

thin film transistor

A transistor/capacitor hybrid that controls color pixels on an LCD grid.

transimpedance amplifier

An amplifer that increases the bandwidth of a signal.

transistor outline

A type of semiconductor packaging. Transistor outline packages are usually shaped like a can and are often called TO cans.

transmitter

A device that sends signals. Optical fibers are used with transmitters to form fiber optic transmitters.

triac

An electronic switch that allows small control voltages and currents to switch very high voltages, as in a lightening controller.

ultraviolet light

A wavelength that is above violet in the color spectrum. Ultraviolet light is not visible to the human eye.

visible light

Wavelengths of electromagnetic radiation that can be seen with the human eye.

wave

The energy that comes from light. Light is made up of rays and waves.

wavelength

The distance between separate peaks of a sine wave. The wavelength of light determines whether or not it is visible to the human eye.

zero bias

A bias that causes a photodiode to conduct current. Bias causes an electrical device to operate in a predetermined manner.