Optical Computing Essay

Jainam Shah Kalol Institute Of Technology, Kalol, Gujarat, India. jainam_8888yahoo.co.in AbstractOptics has been utilise in deliberation for a summate of geezerhood that the main emphasis has been and continues to be to interrelate portions of computing devices, for communication theory, or more as such(prenominal) in devices that founder or so favoric cover or percentage ( ocular pattern recognition, etc). opthalmic digital electronic computers atomic number 18 unfluste blood-red some years away, however a number of devices that thunder mug eventu wholey offer to real opthalmic computers have already been manufactured, including ocular system of logic gates, visual switches, optic interconnections, and optic memory. The most likely near-term opthalmic computer will re eithery be a hybrid composed of conventional architectural design along with some portions that sewer answer some functional operations in optical mode.Computing applications as a consequen ce of abstainer processing revivify, as well as break bring out connectivity and laster bandwidth. II. NEED FOR visual COMPUTING The pressing need for optical technology stems from the fact that todays computers be limited by the time response of electronic circuits. A solid transmission mass medium limits both the belt along and volume of signals, as well as grammatical construction up heat that damages comp peerlessnts. One of the theoretical limits on how fast a computer can function is given by masterminds principle that signal cannot propagate windy than speed of shed lower on. So to contrive computers faster, their comp anents must be small and thither by slack the distance between them. This has resulted in the organic evolution of very large home plate integration (VLSI) technology, with smaller device dimensions and greater complexity. The smallest dimensions of VLSI nowadays be roughly 0.08mm.Despite the incredible pass in the development and refineme nt of the basic technologies over the past decade, there is growing concern that these technologies whitethorn not be cap suit open of solving the computing problems of even the ongoing millennium. The speed of computers was achieved by miniskirtaturizing electronic components to a very small micron-size scale, but they atomic number 18 limited not only by the speed of electrons in reckon but also by the increasing density of interconnections necessary to link the electronic gates on microchips. The optical computer comes as a solution of miniaturization problem. opthalmic information processing can perform several(prenominal) operations in parallel much faster and easier than electrons. This commensu driftness helps in staggering computational power. For example a calculation that takes a conventional electronic computer more than 11 years to get along could be performed by an optical computer in a bingle hour. Any way we can realize that in an optical computer, electrons argon replaced by photons, the subatomic bits of electromagnetic radiation that make up ignite.I. intro With the increase of computing technology the need of amply performance computers (HPC) has importantly increased. Optics has been physical exertiond in computing for a number of years but the main emphasis has been and continues to be to link portions of computers, for communications, or more intrinsically in devices that have some optical application or component (optical pattern recognition etc.) Optical computing was a hot inquiry atomic number 18a in 1980s.But the work tapered off due to materials limitations that prevented opt chips from getting small enough and cheap enough beyond laboratory curiosities. Now, optical computers are subscribe with advances in self-assembled conducting perfect polymers that promise super-tiny of all optical chips. Optical computing technology is, in general, ontogeny in two directions.One approach is to build computers that have th e same architecture as kick in day computers but victimization optics that is Electro optical hybrids. some new(prenominal) approach is to generate a completely new kind of computer, which can perform all functional operations in optical mode. In recent years, a number of devices that can ultimately take away us to real optical computers have already been manufactured. These include optical logic gates, optical switches, optical interconnections and optical memory. Current trends in optical computing emphasize communications, for example the use of free space optical interconnects as a potential solution to remove Bottlenecks experienced in electronic architectures. Optical technology is one of the most promising, and may eventually lead to newIII. SOME KEY OPTICAL COMPONENTS FOR COMPUTING The major break by dint ofs on optical computing have been centered on the development of micro-optic devices for entropy input. A. VCSEL (Vertical Cavity Surface Emitting Laser) VCSEL (pron ounced vixel) is a semiconductor vertical cavity show up emitting optical maser rectifying valve that emits light in a cylindrical get off vertically from the surface of a fabricated wafer, and offers significant advantages when compared to the edge-emitting lasers currently used in the majority of fibre optic communications devices. The principle have-to doe with in the operation of a VCSEL is very similar to those of regular lasers.Fig. 2. Optical Interconnection Of Circuit Boards Using Vcsel And PhotodiodeVCSEL convert the electrical signal to optical signal when the light communicates are cloged through with(predicate) a pair of lenses and micro reflects. Micromirrors are used to direct the light commits and this light rays is passed through a polymer shudder guide which serves as the running for carryting entropy instead of copper wires in electronic computers. Then these optical beams are again passed through a pair of lenses and sent to a photodiode. This photo diode convert the optical signal back to the electrical signal. B. SLM (Spatial Light Modulators) SLM play an important constituent in several technical areas where the control of light on a pixel-by-pixel basis is a key element, such as optical processing and displays. 1) SLM For Display Purposes Fig. 1. cardinal semiconductor materials sandwiching an active layerThere are two particular(prenominal) semiconductor materials sandwiching an active layer where all the action takes place. But kinda than reflective ends, in a VCSEL there are several layers of partly reflective mirrors above and below the active layer. Layers of semiconductors with differing compositions create these mirrors, and each mirror reflects a narrow range of wavelengths back in to the cavity in nightclub to cause light emission at just one wavelength.For display purposes the desire is to have as umpteen pixels as practical in as small and cheap a device as possible. For such purposes designing te chips for use as spatial light modulators has been proceedsive. The basic idea is to have a pit of memory cells pose out on a regular grid. These cells are electrically affiliated to metal mirrors, such that the voltage on the mirror depends on the cling to hold ond in the memory cell. A layer of optically active swimming quartz is sandwiched between this array of mirrors and a piece of glass with a conductive coating. The voltage between individual mirrors and the front electrode affects the optical drill of liquid crystal in that neighborhood. Hence by being able to individually program the memory locations one can set up a pattern of optical activity in the liquid crystal layer. C.Smart Pixel TechnologySmart pixel technology is a relatively new approach to integrating electronic circuitry and optoelectronic devices in a common framework. The purpose is to leverage the advantages of each individual technology and leave alone improved performance for specific applications. Here , the electronic circuitry brooks complex functionality and programmability while the optoelectronic devices bequeath high-speed switching and compatibility with existing optical media. Arrays of these smart pixels leverage the parallelism of optics for interconnections as well as computation. A smart pixel device, a light emitting diode under the control of a field effect transistor can now be made entirely out of organic materials on the same substrate for the first time. In general, the return of organic over conventional semiconductor electronics is that they should lead to cheaper, lighter, circuitry that can be printed rather than etched. D. WDM ( driftlength Division Multiplexing) Wavelength division multiplexing is a method of sending many different wavelengths down the same optical fiber. Using this technology, modern networks in which individual lasers can transmit at 10 gigabits per second through the same fiber at the same time.which interact with light and tone up its properties. Several of the optical components require efficient-nonlinear materials for their operations. What in fact restrains the widespread use of all optical devices is the in efficiency of currently available nonlinear materials, which require large amount of energy for responding or switching. Organic materials have many features that make them desirable for use in optical devices such as 1) luxuriously nonlinearities 2) Flexibility of molecular design 3) Damage enemy to optical radiations Some organic materials belonging to the classes of phthalocyanines and polydiacetylenes are promising for optical turn out films and wave guides.These compounds exhibit strong electronic transitions in the visual region and have high chemical and thermal stability up to 400 degree Celsius. Polydiacetylenes are among the most widely investigated class of polymers for nonlinear optical applications. Their subpicosecond time response to laser signals makes them candidates for high-spee d optoelectronics and information processing. To make thin polymer film for electro-optic applications, NASA scientists dissolve a monomer (the building block of a polymer) in an organic solvent. This solution is then put into a growth cell with a quartz window, shining a laser through the quartz can cause the polymer to deposit in specific pattern. V. ADVANCES IN PHOTONIC SWITCHES Logic gates are the building blocks of any digital system. An optical logic gate is a switch that controls one light beam by an other it is ON when the device transmits light and it is OFF when it blocks the light.Fig. 3.a. Wave length division multiplexing b. A WDM SystemWDM can transmit up to 32 wavelengths through a bingle fiber, but cannot meet the bandwidth requirements of the present day communication systems. So nowadays DWDM (Dense wavelength division multiplexing) is used. This can transmit up to 1000 wavelengths through a single fiber. That is by development this we can improve the bandwidth e fficiency. IV. ROLE OF NLO IN OPTICAL COMPUTING The role of nonlinear materials in optical computing has become extremely significant. Non-linear materials are those, Fig. 4. Optical AND-logic gateTo demonstrate the AND gate in the phthalocyanine film, two cerebrate collinear laser beams are wave guided through a thin film of phthalocyanine. Nanosecond green winkd NdYAG laser was used together with a red continuous wave (cw) He-Ne beam. At the turnout a narrow band filter was set to block the green beam and allow only the He-Ne beam. Then the transmitted beam was detected on an oscilloscope. It was found that the transmitted He-Ne cw beam was pulsating with a nanosecond duration and in coeval with the input NdYAG nanosecond pulse.This demonstrated the characteristic table of an AND logic gate. A. Optical and Gate In an optical NAND gate the phthalocyanine film is replaced by a hollow fiber filled with polydiacetylene. NdYAG green picoseconds laser pulse was sent collinearly wit h red cw He-Ne laser onto one end of the fiber. At the other end of the fiber a lens was focusing the output on to the narrow slit of a monochromatic with its grating set for the red He-Ne laser. When both He-Ne laser and NdYAG laser are present there will be no output at the oscilloscope. If either one or none of the laser beams are present we get the output at the oscilloscope showing NAND function.faster read-out rates. This research is expected to lead to compact, high capacity, rapid-and random-access, and low power and low cost data entrepot devices necessary for future intelligent spacecraft. The SLMs are used in optical data storage applications. These devices are used to write data into the optical storage medium at high speed.Fig. 6.Optical Disk more than conventional approaches to holographic storage use ion doped lithium niobate crystals to investment trust pages of data. For audio recordings ,a 150MBminidisk with a 2.5- in diameter has been developed that uses special abridgement to shrink a standard CDs640-MB storage capacity onto the smaller polymer substrate. It is rewritable and uses magnetic field modulation on optical material. The mini record uses one of the two methods to write information on to an optical disk. With the mini disk a magnetic field placed behind the optical disk is modulated while the intensity of the writing laser is held constant. By switching the polarity of the magnetic field while the laser creates a state of flux in the optical material digital data can be recorded on a single layer. As with all optical storage media a read laser retrieves the data. A. running(a) The 780nm light emitted from AlGaAs/GaAs laser diodes is collimated by a lens and focused to a diameter of about 1micrometer on the disk. If there is no pit where the light is incident, it is reflected at the Al mirror of the disk and returns to the lens, the depth of the pit is set at a value such that the difference between the path of the light reflec ted at a pit and theFig. 5.Optical NAND-logic gateVI. OPTICAL MEMORY In optical computing two types of memory are discussed. One consists of arrays of one-bit-store elements and other is mass storage, which is implemented by optical disks or by holographic storage systems. This type of memory promises very high capacity and storage density. The primary benefits offered by holographic optical data storage over current storage technologies include significantly higher(prenominal) storage capacities and path of light reflected at a mirror is an constitutional multiple of halfwavelength consequently, if there is a pit where light is incident, the amount of reflected light decreases tremendously because the reflected lights are almost cancelled by incumbrance.The incident and reflected beams pass through the quarter wave plate and all reflected light is introduced to the photodiode by the beam splitter because of the polarization rotation due to the quarter wave plate. By the photodiod e the reflected light, which as a signal whether, a pit is on the disk or not is changed into an electrical signal. VII. APPLICATIONS 1) High speed communications The rapid growth of internet, expanding at almost 15% per month, demands faster speeds and large bandwidth than electronic circuits can provide.Terabits speeds are needed to accommodate the growth rate of internet since in optical computers data is transmitted at the speed of light which is of the order of 3.10*8 m/sec hence terabit speeds are attainable. 2) Optical crossbar interconnects are used in asynchronous transfer modes and divided memory multiprocessor systems. 3) Process satellite data. VIII. MERITS 1) Optical computing is at least(prenominal) 1000 to 100000 times faster than todays silicon machines. 2) Optical storage will provide an extremely optimized way to store data, with space requirements far lesser than todays silicon chips. 3) A-one fast searches through databases.4) No short circuits, light beam ca n cross each other without interfering with each others data 5) Light beams can travel in parallel and no limit to number of packets that can travel in the photonic circuits. 6) Optical computer removes the bottleneck in the present day Communication system IX. DRAWBACKS 1) like a shots materials require much high power to work in consumer products, coming up with the right materials may take five years or more. 2) Optical computing using a coherent credit is simple to compute and understand, but it has many drawbacks like any imperfections or dust on the optical components will create unwanted interference pattern due to scattering effects. Incoherent processing on the other hand cannot store phase information.X. SOME CURRENT RESEARCH High performance computing has gained momentum in recent years, with efforts to optimize all the resources of electronic computing and researcher brain power in order to increase computing throughput. Optical computing is a topic of current support in many places, with private companies as well as governments in several countries encouraging such research work. A sort of researchers from the University of Southern California, jointly with a team from the University of California, los angles, have developed an organic polymer with a switching frequency of 60 GHz. This is three times faster than the current industry standard, lithium niobate crystal based device.Another root word at brown university and the IBM, Alma den research center has used ultrafast laser pulses to build ultra fast data storage devices. This group was able to achieve ultra fast switching down to 100 picoseconds. In Japan , NEC has developed a method for interconnecting circuit boards optically using VCSEL arrays .Another researchers at NTT have designed an optical backplane with free-space optical interconnects using tunable beam deflectors and mirrors. The project achieved 1000 interconnections per printed circuit board with a throughput ranging from 1 to 10 Tb/s. XI. FUTURE TRENDS The Ministry of Information Technology has initiated a photonic development program. Under this program some funded projects are continuing in fiber optic high-speed network systems. Research is going on for developingFig.7. Use of optical devices in futureNew laser diodes, photo detectors, and nonlinear material studies for faster switches. Research efforts on an particle thin film or layer studies for display devices are also in progress. At the Indian Institute of Technology (IIT), Mumbai, efforts are in progress to generate a white light source from a diode case based fiber amplifier system in order to provide WDM communication channels. XII. CONCLUSION Research in optical computing has exposed up new possibilities in several fields related to high performance computing, high-speed communications. To design algorithms that execute applications faster, the specific properties of optics must be considered, such as their ability to exploit massive par allelism, and global interconnections. As optoelectronic and smart pixel devices mature, software development will have a major impact in the future and the ground rules for the computing may have to be rewritten.XIII. REFERENCES1 2 See for example Chemical and Engineering ews, Photonic Crystals. Assembled on Chip, 79(47), 31 (2001). P. Boffi, D. Piccinin, M.C. Ubaldi, (Eds.), Infrared Holography for Optical Communications echniques,MaterialsandDevices,SpringerTopics in apply Physics Vol 86, July 2002. Alain Goulet, Makoto Naruse, and Masatoshi Ishikawa, Simple integration technique to realize parallel optical interconnects implementation of a pluggable two-dimensional optical data link, utilise Optics 41, 5538 (2002) Tushar Mahapatra, Sanjay Mishra, Oracle Parallel Processing, OReilly & Associates, Inc., Sebastopol, California, USA, 2000. S. J. van Enk, J. McKeever, H. J. Kimble, and J. Ye, Cooling of a single atom in an optical trap inside a resonator, Phys. Rev. A 64, 013407 (2 001). A. Dodabalapur, Z. Bao, A. Makhija, J. G. Laquindanum, V. R. Raju, Y. Feng, H. E. Katz, and J. Rogers, Organic smart pixels, Appl. Phys. Lett. 73, 142 (1998). Henning Sirringhaus, Nir Tessler, and Richard H. Friend, Integrated Optoelectronic Devices Based on Conjugated Polymers, acquaintance 280, 1741 (1988).