Photonic (Optical) Computing by sin15395

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									Photonic (Optical) Computing




          Jason Plank
         Topics to be Addressed
   What is photonic computing?
   How does it compare to conventional electronic
    computing?
   How is it done?
   What are the challenges imposed by photonic
    computing?
   What can it do?
   What is the current progress of research?
                Nomenclature
   Electronics – the movement of electrons
        Derived from electrons – subatomic particles
         which carry electrical charge
   Photonics – the movement of light
        Derived from photons – the ”units” of light
        Photons have properties of both particles and
         waves
        The term ”photonic computing” is used
         interchangeably with ”optical computing”
    Current Standards of Computing
    Electronic computing is the conventional standard
    Today's computers use processors that control and
     manipulate the flow of electrons
         Signal processing occurs when electrons are sent
          through a semiconductive material such as silicon
         The semiconductive material controls and
          manipulates the flow of electrons
         These materials make up what we know as CPUs
    Limitations of Electronics and
       Electronic Computing
   The speed of electrons through electrically
    conductive and semiconductive materials
   Signal loss and electromagnetic interference
   Electrical current generates heat
   Greater computational speed requires increased
    current, resulting in increased heat
   Not well-suited to image processing as opposed to
    numerical processing
     Advantages of Photonics and
        Photonic Computing
   In photonic devices, information travels at the
    speed of light
        Increased throughput over electronic devices
   Signal loss is much less significant when
    compared to signal loss in electronics
   No interference between intersecting beams
   Generates insignificant amounts of heat
    regardless of how much light is directed through
    circuits
   Photonic processors are well-suited to image
    processing whereas electronic processors are not
    Challenges of Photonic Computing
    Materials which act as processors for photons are
     still in early development and research
         Act as an analog to the electronic semiconductor
         These materials are called photonic crystals
    Without these processors, optical signals need to
     be generated and interpreted via electronic means
         Example: fiber optics of today
             Photonic Crystals
   Photonic crystals are structures which control
    and/or manipulate the flow of photons
   Also known as photonic band-gap structures
   Analogous to the electronic transistor
   Must be made with extreme precision
        Not easily manufactured
   Once successfully miniaturized, photonic crystals
    may be used as the building blocks of optical
    integrated circuits
    Photonic Crystals, continued
                                      Designed to reflect,
                                       refract, and/or ”bend”
                                       light of a specific
                                       wavelength
                                      Slow or trap light in
                                       specialized
                                       microcavities
False-color closeup of a silicon
       photonic crystal
                                      May make optical
    Source: Science News
                                       memory systems
                                       possible
Applications of Photonic Computing
   Photonic circuitry may first be used as
    replacements for electronic components in
    conventional hardware
        This results in a hybrid optical/electronic
         (optoelectronic) computer system
        Seems to be the most likely approach for early
         photonic applications
   Purely photonic computers
        Would be comprised of all-optical components
    The von Neumann Bottleneck
   The von Neumann Bottleneck refers to the limited
    data transfer rate (throughput) resulting from the
    separation of CPU and memory
   Due to this bottleneck, increases in CPU speed
    result in diminishing returns in throughput
   Caching and parallel computing reduce the
    bottleneck's impact but do not eliminate it
Von Neumann Bottleneck, continued
   There is some speculation that photonic
    computers may not suffer from this bottleneck
   Processors may contain much more memory




     Source: cs.cmu.edu
         Photonic Crystal Research
   A handful of scientists have built photonic
    crystals
   Currently, research aims to increase efficiency
         A technique for building a photon switch which
          operates using single photons has been developed
         This is an improvement of a technique which used
          a burst of photons to operate the switch
   Reducing power consumption increases the
    feasibility of potential optical components
             Topics Discussed
   What photonic computing is
   How it compares to conventional computing
   How it is done
   Challenges of photonic computing
   The applications of photonic computing
   What research has been and is being done in the
    field of photonic computing
                           References
   Amato, I. (1992). Designing crystals that say no to photons. Science, New
    Series, 255(5051) 1512.
   Chang, D. E, Sørensen, A. S, Demler, E. A, & Lukin, M. D. (2007). A single-
    photon transistor using nano-scale surface plasmons. Retrieved from
    http://arxiv.org/abs/0706.4335v1
   Das, S. (2007). Speed-of-light computing comes a step closer. New Scientist,
    2613, 28.
   Session 13: digital design. Retrieved from http://www.cs.cmu.edu/~ref
    /pgss/lecture/11/index.html
   Taubes, G. (1997). Photonic crystal made to work at an optical wavelength.
    Science, New Series, 278(5344) 1709-1710.
   Weiss, P. (2005). Light pedaling. Science News, 168(19), 292.
   Weiss, P. (2004). Lighthearted transistor. Science News, 166(21), 324.
   Yablonovitch, E. (2000). How to be truly photonic. Science, New Series,
    289(5479), 557 + 559.

								
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