A photonic integrated circuit or integrated optical circuit is a device
that integrates multiple photonic functions and as such is similar to an
electronic integrated circuit. The major difference between the two is that a
photonic integrated circuit provides functionality for information signals
imposed on optical wavelengths typically in the visible spectrum or near infrared
850 nm-1650 nm. The most commercially utilized material
platform for photonic integrated circuits is indium phosphide, which
allows for the integration of various optically active and passive functions
on the same chip. Initial examples of photonic integrated circuits were simple
2 section distributed Bragg reflector lasers, consisting of two independently
controlled device sections - a gain section and a DBR mirror section.
Consequently, all modern monolithic tunable lasers, widely tunable lasers,
externally modulated lasers and transmitters, integrated receivers, etc.
are examples of photonic integrated circuits. Current state-of-the-art
devices integrate hundreds of functions onto single chip. Pioneering work in
this arena was performed at Bell Laboratories. Most notable academic
centers of excellence of photonic integrated circuits in InP are the
University of California at Santa Barbara, USA, and the Eindhoven
University of Technology in the Netherlands.
Recently, a large amount of funding has been invested into developing photonic
integrated circuits in silicon. A 2005 development showed that silicon
can, even though it is an indirect bandgap material, still be used to
generate laser light via the Raman nonlinearity. Such lasers are not
electrically driven but optically driven and therefore still necessitate a
further optical pump laser source. Comparison to electronic integration
Unlike electronic integration where silicon is the dominant material, system
photonic integrated circuits have been fabricated from a variety of material
systems, including electro-optic crystals such as lithium niobate, silica
on silicon, Silicon on insulator, various polymers and semiconductor
materials which are used to make semiconductor lasers such as GaAs and
InP. The different material systems are used because they each provide different
advantages and limitations depending on the function to be integrated. For
instance, silica based PICs have very desirable properties for passive
photonic circuits such as AWGs due to their comparatively low losses and low
thermal sensitivity, GaAs or InP based PICs allow the direct integration of
light sources and Silicon PICs enable co-integration of the photonics with
transistor based electronics. The fabrication techniques are similar
to those used in electronic integrated circuits in which photolithography is
used to pattern wafers for etching and material deposition. Unlike electronics
where the primary device is the transistor, there is no single dominant
device. The range of devices required on a chip includes low loss interconnect
waveguides, power splitters, optical amplifiers, optical modulators, filters,
lasers and detectors. These devices require a variety of different materials
and fabrication techniques making it difficult to realize all of them on a
single chip. Newer techniques using resonant photonic
interferometry is making way for UV LEDs to be used for optical computing
requirements with much cheaper costs leading the way to PHz consumer
electronics. Examples of photonic integrated circuits
The primary application for photonic integrated circuits is in the area of
fiber-optic communication though applications in other fields such as
biomedical and photonic computing are also possible.
The arrayed waveguide grating which are commonly used as opticalmultiplexers in
wavelength division multiplexed fiber-optic communication systems are an
example of a photonic integrated circuit which has replaced previous multiplexing
schemes which utilized multiple discrete filter elements. Since separating
optical modes is a need for quantum computing, this technology may be
helpful to miniaturize quantum computers.
Another example of a photonic integrated chip in wide use today in fiber-optic
communication systems is the externally modulated laser which combines a
distributed feed back laser diode with an electro-absorption modulator on a
single InP based chip. Advantages of photonic circuits
Photonic integrated circuits can allow optical systems to be made more compact
and higher performance than with discrete optical components. They also
offer the possibility of integration with electronic circuits to provide
increased functionality. One challenge to achieving this level of
integration is the size discrepancy between electronic and photonic
components. The emerging field of nanoplasmonics is focused on creating
ultracompact components for realizing truly nanoscale photonic devices to
match their electronic counterparts. An example of the new breed of
components is a recently proposed novel type of bandpass plasmonic filter that
uses a response similar to electromagnetically induced transparency
to achieve multichannel filtering. This allows easy control over the filtering
wavelengths and bandwidths for applications in wavelength multiplexing
systems for optical computing and communications in highly integrated
all-optical circuits. Photonic integrated circuits should also
be immune to the hazards of functionality losses associated with
electromagnetic pulse, though may not be immune to high neutron flux.
Current status Photonic integration is currently an
active topic in U.S. Defense contracts: "Silicon-based Photonic Analog Signal
Processing Engines with Reconfigurability - Federal Business
Opportunities: Opportunities". Fbo.gov. Retrieved 2013-12-21.
"Centers in Integrated Photonics Engineering Research - Federal Business
Opportunities: Opportunities". Fbo.gov. Retrieved 2013-12-21.
It is included by the Optical Internetworking Forum for inclusion in
100 gigahertz optical networking standards: contracts:
CEI-28G: Paving the Way for 100 Gigabit Infinera Corp. develops and vertically
integrates 100 Gb/s and 500 Gb/s photonic integrated circuits in
commercially available long haul optical transport networking platforms
Infinera's 500 Gb/s PIC was named "Best Optical Component Beyond 100G" at the
2013 Next Generation Optical Awards See also
Nanophotonics Optical computing
References Notes
References Larry Coldren; Scott Corzine; Milan
Mashanovitch. Diode Lasers and Photonic Integrated Circuits. John Wiley and
Sons. McAulay, Alastair D.. Optical Computer
Architectures: The Application of Optical Concepts to Next Generation
Computers. Guha, A.; Ramnarayan, R.; Derstine, M..
"Proceedings of the 14th annual international symposium on Computer
architecture - ISCA '87": 145. doi:10.1145/30350.30367. ISBN
0818607769. Altera Corporation. "Overcome Copper
Limits with Optical Interfaces". Brenner, K.-H.; Huang, Alan. "Logic and
architectures for digital optical computers". J. Opt. Soc. Am. A3: 62.
Bibcode:1986OSAJ....3...62B. Brenner, K.-H.. "A programmable optical
processor based on symbolic substitution". Appl. Opt. 27: 1687–1691.
Bibcode:1988ApOpt..27.1687B. doi:10.1364/AO.27.001687. PMID 20531637.