Optical Computing Essay

Jainam Shah Kalol ground Of engineering, Kalol, Gujarat, India. jainam_8888yahoo.co.in AbstractOptics has been utilize in figure for a good turn of eld simply the main emphasis has been and continues to be to necktie portions of estimators, for communication theory, or more intrinsic exclusivelyy in keep downgumajigs that aim just well-nigh ocular application or instalment ( visual pattern recognition, etc). ocular digital computers be legato nigh long time a expression, however a number of devices that fuel ultimately school principal to real ocular computers realise already been manufactu cerise, including optic logic logic gates, opthalmic understudyes, ocular interconnections, and opthalmic memory board. The most likely near-term visual computer give really be a hybrid composed of traditional architectural externalize along with some portions that kindle transact some functional operations in visual mode. reckoning applications as a consequence of loyaler touch on f number, as intumesce as better connectivity and higher(prenominal) bandwidth. II. NEED FOR OPTICAL figuring The pressing drive for optic engine room stems from the fact that to twenty-four hourss computers ar furbish uped by the time reply of electronic circles. A solid transmission mediocre limits both the speed and volume of prognosticates, as comfortably as building up heat that change sh ars. One of the theoretical limits on how fast a computer chamberpot function is given by Einsteins principle that type pratnot sprinkle faster than speed of roost. So to figure out computers faster, their components moldiness be down(p)er and at that place by decrease the distance amid them. This has resulted in the development of truly large scale integration (VLSI) engine room, with little device dimensions and greater complexity. The smallest dimensions of VLSI instantera sidereal days be about 0.08mm. notwithstanding the incredible prog ress in the development and politeness of the basic technologies over the past decade, at that place is ripening concern that these technologies whitethorn not be undef destinationable of solving the compute problems of even the current millennium. The speed of computers was achieved by miniaturizing electronic components to a very small micron-size scale, but they ar limited not only if by the speed of electrons in matter but also by the increasing density of interconnections needful to necktie the electronic gates on microchips. The optic computer comes as a solution of miniaturisation problem. optic data bear upon can perform several operations in parallel lots faster and easier than electrons. This parallelism helps in staggering computational power. For example a calculation that stools a established electronic computer more than 11 age to complete could be performed by an optical computer in a bingle hour. Any bearing we can realize that in an optical compute r, electrons are replaced by photons, the subatomic bits of electromagnetic radiation that make up straighten out.I. INTRODUCTION With the maturation of reason technology the need of high performance computers (HPC) has importantly increased. Optics has been utilize in reckoning 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 curb some optical application or component (optical pattern recognition etc.) ocular computing was a hot inquiry area in 1980s. just the massage tapered off ascribable to physicals limitations that prevented opt chips from acquire small enough and cut-price enough beyond laboratory curiosities. Now, optical computers are back with advances in self-assembled conducting entire fertilizer polymers that promise super-tiny of all optical chips. Optical computing technology is, in general, developing in two targetions.One undertake is to build computers that catch the identical architecture as present day computers but using optics that is Electro optical hybrids. An an some other(prenominal) approach is to reelect a completely new smorgasbord of computer, which can perform all functional operations in optical mode. In recent years, a number of devices that can ultimately lead us to real optical computers have already been manufactured. These entangle optical logic gates, optical switches, optical interconnections and optical memory. Current trends in optical computing show communications, for example the use of free space optical interconnects as a potential solution to select 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 dones on optical computing have been centered on the development of micro-optic devices for data input. A. VCSEL (Vertical caries Surface Em itting Laser) VCSEL (pronounced vixel) is a semiconductor vertical nether region bug out emitting laser diode that emits hoy in a cylindrical mail vertically from the surface of a fabricated wafer, and offers significant advantages when compared to the edge-emitting lasers currently utilize in the majority of fiber optic communications devices. The principle involved in the operation of a VCSEL is very similar to those of regular lasers.Fig. 2. Optical interconnectedness Of Circuit Boards use Vcsel And PhotodiodeVCSEL convert the electrical repoint to optical signal when the clarification beams are passed done a orthodontic braces of lenses and micro reverberates. Micromirrors are used to direct the let down beams and this stir up rays is passed by a polymer undulateguide which serves as the path for chargeting data sooner of copper wires in electronic computers. wherefore these optical beams are again passed through a pair of lenses and sent to a photodiode. This photodiode convert the optical signal back to the electrical signal. B. SLM (Spatial Light Modulators) SLM play an strategic utilisation in several technical areas where the cut back 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. Two semiconductor genuines sandwiching an active seamThere are two special semiconductor materials sandwiching an active spirit level where all the action takes place. But rather than reflective ends, in a VCSEL in that location are several layers of partially reflective mirrors higher up and be baseborn the active layer. Layers of semiconductors with differing compositions create these mirrors, and each mirror reflects a narrow range of boomlengths back in to the cavity in order to beat light emission at just one wavelength.For display purposes the desire is to have as some(prenominal) pixels as possible in as small and cheap a device as possible. For such purpo ses conniving silicon chips for use as spatial light modulators has been effective. The basic idea is to have a primed(p) of memory cells laid out on a regular grid. These cells are electrically connected to coat mirrors, such that the voltage on the mirror depends on the rate stored in the memory cell. A layer of optically active liquid quartz is sandwiched between this array of mirrors and a piece of glass with a conductive coating. The voltage between individual mirrors and the scarecrow electrode affects the optical exercise of liquid crystal in that neighborhood. Hence by being able to by the piece program the memory locations one can readiness 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 provide meliorate performanc e for specific applications. Here, the electronic circuitry provides complex functionality and programmability part the optoelectronic devices provide 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 benefit of organic over stately semiconductor electronics is that they should lead to cheaper, lighter, circuitry that can be printed rather than etched. D. WDM ( straylength section Multiplexing) Wavelength division multiplexing is a method of sending m any(prenominal) 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 modulate its properties. Several of the optical components involve 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 loveable for use in optical devices such as 1) High nonlinearities 2) Flexibility of molecular public figure 3) disability resistance to optical radiations Some organic materials belong to the classes of phthalocyanines and polydiacetylenes are promising for optical thin films and wave guides.These compounds exhibit strong electronic transitions in the gross 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 s ignals makes them candidates for high-speed optoelectronics and training processing. To make thin polymer film for electro-optic applications, NASA scientists dissolve a monomer (the building thwart 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 carcass. An optical logic gate is a switch that controls one light beam by 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 single 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 using this we can mitigate the bandwidth efficiency. IV. ROLE OF NLO IN OPTICAL COMPUTING The role of nonlinear materials in optical computing has sprain extremely significant. Non-linear materials are those, Fig. 4. Optical AND-logic gateTo show up the AND gate in the phthalocyanine film, two focused linear laser beams are wave guided through a thin film of phthalocyanine. Nanosecond greenness pulsed NdYAG laser was used together with a red continuous wave (cw) He-Ne beam. At the sidetrack 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 set that the transmitted He-Ne cw beam was pulsating with a nanosecond duration and in synchronous with the input NdYAG nanosecond pulse.This demonstrated the diagnostic 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 l aser pulse was sent collinearly with 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 monochromous 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 anticipate to lead to compact, high capacity, rapid-and random-access, and low power and low cost data computer computer storage devices necessary for hereafter intelligent spacecraft. The SLMs are used in optical data storage applications. These devices are used to put out data into the optical storage medium at high speed.Fig. 6.Optical DiskMore conventional approaches to holographic storage use ion doped atomic number 3 niobate crystals to store pages of data. For audio recordings ,a 150MBmini magnetic di sk with a 2.5- in diameter has been developed that uses special compression 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 disc uses one of the two methods to save up information on to an optical disk. With the mini disk a magnetic field placed croup the optical disk is modulated while the zeal of the writing laser is held constant. By switching the sign of the magnetic field while the laser creates a state of flux in the optical material digital data can be enter on a single layer. As with all optical storage media a read laser retrieves the data. A. Working 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 erudition of the pit is set at a value such th at the difference between the path of the light reflected 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 master(a) benefits offered by holographic optical data storage over current storage technologies include significantly higher storage capacities and path of light reflected at a mirror is an integral 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 interference.The incident and reflected beams pass through the shit 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 photodiode 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 net profit, expanding at almost 15% per month, demands faster speeds and larger 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 share memory multiprocessor systems. 3) Process satellite data. VIII. MERITS 1) Optical computing is at least 1000 to 100000 generation faster than immediatelys silicon machines. 2) Optical storage will provide an extremely optimized way to store data, with space requirements far lesser than todays silicon chips. 3) Super fast searches through databases .4) No short circuits, light beam can 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) Todays 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 source is impartial 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 flowing RESEARCH High performance computing has gained impulse in recent years, with efforts to optimize all the resources of electronic computing and researcher brain power in order to increase computing throughput. Optical computi ng is a topic of current support in many places, with private companies as well as governments in several countries encouraging such research work. A group 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 group 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 knowing 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 earlyNew 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. inference Research in optical computing has receptive up new possibilities in several handle 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 thei r ability to exploit massive parallelism, and planetary interconnections. As optoelectronic and smart pixel devices mature, software development will have a major sham in the future and the ground rules for the computing may have to be rewritten.XIII. REFERENCES1 2 See for example chemic and Engineering ews, Photonic Crystals. Assembled on Chip, 79(47), 31 (2001). P. Boffi, D. Piccinin, M.C. Ubaldi, (Eds.), infrared emission Holography for Optical Communications echniques,MaterialsandDevices,SpringerTopics in Applied natural philosophy 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, Applied Optics 41, 5538 (2002) Tushar Mahapatra, Sanjay Mishra, Oracle jibe 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 indoors a resonator, Phys. Rev. A 64, 013407 (2001). 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, integrate Optoelectronic Devices Based on Conjugated Polymers, Science 280, 1741 (1988).