Optical computing
- Not to be confused with optical computer equipment, like optical mice, optical drives like CD and DVD-ROMs.
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Optical or photonic computing uses photons produced by lasers or diodes for computation. Photons promise to allow a higher bandwidth than the electrons used in conventional computers.
Most research projects focus on replacing current computer components with optical equivalents, resulting in an optical digital computer system processing binary data. This approach appears to offer the best short-term prospects for commercial optical computing, since optical components could be integrated into traditional computers to produce an optical-electronic hybrid. However, optoelectronic devices lose 30% of their energy converting electrons into photons and back. This also slows down transmission of messages. All-optical computers eliminate the need for optical-electrical-optical (OEO) conversions.[1]
Application-specific devices such as optical correlators have been designed that use principles of optical computing. Such devices can be used for detecting and tracking objects, for example.[2]
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Optical components for binary digital computer[edit]
The fundamental building block of modern electronic computers is the transistor. To replace electronic components with optical ones, an equivalent optical transistor is required. This is achieved using materials with a non-linear refractive index. In particular, materials exist[3] where the intensity of incoming light affects the intensity of the light transmitted through the material in a similar manner to the voltage response of an electronic transistor. Such an "optical transistor"[4][5] can be used to create optical logic gates,[5] which in turn are assembled into the higher level components of the computer's CPU. These will be non linear crystals used to manipulate light beams into controlling others.
Controversy[edit]
Although there are disagreements among researchers about the future capabilities of optical computers: will they be able to compete with semiconductor-based electronic computers on speed, power consumption, cost, and size? Opponents of the idea that optical computers can be competitive note that[6] real-world logic systems require "logic-level restoration, cascadability, fan-out and input–output isolation", all of which are currently provided by electronic transistors at low cost, low power, and high speed. For optical logic to be competitive beyond a few niche applications, major breakthroughs in non-linear optical device technology would be required, or perhaps a change in the nature of computing itself.
Photonic logic[edit]
Photonic logic is the use of photons (light) in logic gates (NOT, AND, OR, NAND, NOR, XOR, XNOR). Switching is obtained using nonlinear optical effects when two or more signals are combined.[5]
Resonators are especially useful in photonic logic, since they allow a build-up of energy from constructive interference, thus enhancing optical nonlinear effects.
Other approaches currently being investigated include photonic logic at a molecular level, using photoluminescent chemicals. In a recent demonstration, Witlicki et al. performed logical operations using molecules and SERS.[7]
Further reading[edit]
- Feitelson, Dror G. (1988). Optical Computing: A Survey for Computer Scientists. Cambridge, MA: MIT Press. ISBN 0-262-06112-0.
- McAulay, Alastair D. (1991). Optical Computer Architectures: The Application of Optical Concepts to Next Generation Computers. New York, NY: John Wiley & Sons. ISBN 0-471-63242-2.
- Ibrahim TA, Amarnath K, Kuo LC, Grover R, Van V, Ho PT. Photonic logic NOR gate based on two symmetric microring resonators. Opt Lett. 2004 Dec 1;29(23):2779-81.
- Biancardo M et al. A potential and ion switched molecular photonic logic gate, Chem. Commun., 2005, (31), 3918-3920
- J. Jahns and S. H. Lee, eds., "Optical Computing Hardware", Academic Press, Boston (1994).
- BARROS S., GUAN S. & ALUKAIDEY T., "An MPP reconfigurable architecture using free-space optical interconnects and Petri net configuring" in Journal of System Architecture (The EUROMICRO Journal) Special Double Issue on Massively Parallel Computing Systems vol. 43, no. 6 & 7, pp. 391–402, April 1997
- D. Goswami, "Optical Computing", Resonance, June 2003; ibid July 2003. Web Archive of www.iisc.ernet.in/academy/resonance/July2003/July2003p8-21.html
- Todd Main, Robert J. Feuerstein, Harry F. Jordan, Vincent P. Heuring, John Feehrer, and Carl E. Love, "Implementation of a general-purpose stored-program digital optical computer," Applied Optics, Vol. 33, pp. 1619–1628 (1994) (http://www.opticsinfobase.org/abstract.cfm?URI=ao-33-8-1619)
- T.S. Guan & S.P.V. Barros, "Reconfigurable Multi-Behavioural Architecture using Free-Space Optical Communication" in Proceedings of the IEEE International Workshop on Massively Parallel Processing using Optical Interconnections., April 1994
- T.S. Guan & S.P.V. Barros, "Parallel Processor Communications through Free-Space Optics" in IEEE Region 10's Ninth Annual International Conference on Frontiers of Computer Technology, August 1994
- Architectural issues in designing symbolic processors in optics
- K.-H. Brenner, Alan Huang: "Logic and architectures for digital optical computers (A)", J. Opt. Soc. Am., A 3, 62, (1986)
- K.-H. Brenner: "A programmable optical processor based on symbolic substitution", Appl. Opt. 27, No. 9, 1687–1691, (1988)
- N. Streibl, K.-H. Brenner, A. Huang, J. Jahns, J. L. Jewell, A. W. Lohmann, D.A.B. Miller, M. J. Murdocca, M. E. Prise, and T. Sizer II, Digital Optics, Proc. IEEE 77, 1954-1969 (1989)
- NASA scientists working to improve optical computing technology
- Optical solutions for NP-complete problems
- 1st International Workshop on Optical SuperComputing 2008
- 2nd International Workshop on Optical SuperComputing 2009
- 3rd International Workshop on Optical SuperComputing 2010
- 4th International Workshop on Optical SuperComputing 2012
- Speed-of-light computing comes a step closer New Scientist
References[edit]
- ^ Mind at Light Speed, David Nolte, page 34
- ^ Feitelson, Dror G. (1988). "Chapter 3: Optical Image and Signal Processing". Optical Computing: A Survey for Computer Scientists. Cambridge, MA: MIT Press. ISBN 0-262-06112-0.
- ^ http://www.rp-photonics.com/nonlinear_index.html
- ^ Jain, K. and Pratt, Jr., G. W., "Optical transistor", Appl. Phys. Lett., Vol. 28, 719 (1976).
- ^ a b c Jain, K. and Pratt, Jr., G. W., "Optical transistors and logic circuits embodying the same", U.S. Pat. 4,382,660, issued May 10, 1983.
- ^ R.S. Tucker, "The role of optics in computing", Nature Photonics, no.4, p. 405.
- ^ Witlicki, Edward H.; Johnsen, Carsten; Hansen, Stinne W.; Silverstein, Daniel W.; Bottomley, Vincent J.; Jeppesen, Jan O.; Wong, Eric W.; Jensen, Lasse; Flood, Amar H. (2011). "Molecular Logic Gates Using Surface-Enhanced Raman-Scattered Light". J. Am. Chem. Soc. 133 (19): 7288–7291. doi:10.1021/ja200992x.
External links[edit]
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