ABSTRACTPhotonic Computing is digital computing in imitation of conventional electronic computing only using laser light instead of electricity, and holograms instead of silicon computer chips. "Photonic" comes from "photon" which is the smallest unit of light just as an electron is the smallest unit of electricity. "Photon" comes from "photo" as in "Kodak moment!" Uninhibited light travels thousands of times faster than electrons in computer chips; therefore it is capable of computing thousands of times faster than electronic computing. The photonic transistor products, which are expected to replace much of the electronics infrastructure during the 21st century, can be made smaller, faster, and cheaper. They are more reliable, generate less heat, and are not susceptible to interference from outside influences. Photonic computers use the transfer and manipulation of photons, which are pulses of light, as a means of transferring and performing calculations of data. For performing calculations, Photonic computers manipulate the flow of electrons through logic gates composed of transistors, which acts like switches – located in the computer's Central Processing Unit. Photonic computers, like modern computers, works in a similar fashion in the sense that they both transfer and manipulate data in the form of bits, however, unlike traditional computers where bits are represented as electrons, Photonic computers represent bits in the form of photons. The Photonic computer uses only light to collect, retrieve, and process data. This makes it operate much faster than electronically based computers because information and processing occurs at the speed of light. Another key benefit of the Photonic computer is that less energy is used to power the system and it does not have the same interference problems that make it difficult for current chip manufacturers to make smaller transistors. This is because light energy does not interact with other photons. The processor itself is a laser inscribed piece of crystal made in the laboratory and the current system uses only a huge amount of RAM to store information. Although this system is complete, it is still very simple and not very useful. INTRODUCTION Photonic computing is digital computing in replication of conventional electronic computing only using laser light instead of electricity and holograms instead of silicon computer chips. Photonic comes from photon which is the smallest unit of light just as an electron is the smallest unit of electricity. Photon comes from photo. Uninhibited light travels thousands of times faster than electrons in computer chips therefore, it is capable of computing thousands of times faster than electronic computing. Therefore, light computers compute thousands of times faster than any electronic computer can ever due to the physical limitation differences between light and electricity With today's growing dependence on computing technology, the need for high performance computers (HPC) has significantly increased. With the help of virtual product design and development, costs can be reduced. Hence looking for improved computing capabilities is desirable. Optical computing includes the optical calculation of transforms and optical pattern matching. Emerging technologies also make the optical storage of data a reality. The speed of computers was achieved by miniaturizing electronic components to a very small micron-size scale, but they are limited not only by the speed of electrons in matter (signals cannot propagate faster than the speed of light) 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. In an optical computer, electrons are replaced by photons, the subatomic bits of electromagnetic radiation that make up light. Electronic computing uses electrons to perform the logic that makes computing work. Photonic computing uses photons of laser light to do the same job. Electronic transistors are whittled into silicon wafers to make modern computer chips. Today's technology, however, is pushing the electron to its physical limits. As a result, the manufacturing processes are becoming increasingly expensive for producing even minor improvements. However, photons are manipulated using inexpensive computer-generated holograms made of plastic or glass. most telephone companies have been investing heavily in the global conversion from copper wire to optical fiber because light does a better job of carrying information than does electricity. If we can just get them to accomplish the logic tasks that make computing work. allowing photonic devices to process multiple streams of data simultaneously. electronic circuits and wires will be replaced by a few optical fibers and films. photons are inherently more valuable than electrons. making the systems more efficient with no interference. multiple frequencies (or different colors) of light can travel through optical components without interfacing with each others. Indeed. Thus. more cost effective. . will be far more valuable than their slower electronic counterparts. lighter and more compact. In the photonic computer of the future. This is because photons (the basic unit of light) go faster. Interestingly.Photonic computers. they will become the next logical computing upgrade. and far less expensive to manufacture. therefore. and have a higher bandwidth than do electrons. Optical components would not need to have insulators as those needed between electronic components because they do not experience cross talk. while photonics often refers to more application-related research. transmission. Photonic devices include optoelectronic devices such as lasers and photodetectors. the overlap between all of these fields and "optics" is unclear. Figure 1. modulation. In addition. Quantum optics frequently implies fundamental research.1 – Refraction of photons by a prism The science of photonics includes the emission. particularly in the visible and near infra-red spectrum. . detection. photonic crystals. amplification. and switching of light. The term optoelectronics. which by construction is a somewhat narrower field than photonics dealing only with active elements involving an electrical interaction. The term photonics may. nonetheless frequently is used to include passive photonic elements as well. as well as optical fiber. controlling and detecting photons. planar waveguides and other passive optical elements.Concept: Photonics: a related term: Photonics is the science and technology of generating. and different definitions are used in different parts of the world and in different industries. but doesn't always. Photonics as a science is closely related to quantum optics and optoelectronics with somewhat unclear boundaries. imply a goal of establishing an electronics of photons instead of electrons. vision correction. and optical computing. and the Erbium-doped fiber amplifier.Applications of photonics include: • • • • • • • • • • • • • • light detection telecommunications information processing illumination metrology spectroscopy holography medicine (surgery. biological and chemical sensing. These inventions formed the basis for the telecommunications revolution of the late 20th Century. Various non-telecom photonics applications exhibit a strong growth particularly since the dot-com crash. followed in the 1970s by the development of optical fibers as a medium for transmitting information using light beams. including: laser manufacturing. . medical diagnostics and therapy. History of photonics: Photonics as a field really began in 1960. endoscopy. health monitoring) laser material processing visual art biophotonics agriculture robotics defense. However. Photonics as a field was largely focused on communications. partly because many companies have been looking for new application areas quite successfully. display technology. and provided the infrastructure for the Internet. with the invention of the laser. photonics covers a huge range of science and technology applications. A huge further growth of photonics can be expected for the case that the current development of silicon photonics will be successful. As you might expect.5 femtoseconds (fs). The photonic transistor has been shown to have a tuning and filtering resolution finer than that of an AM radio. the photonic transistors now being developed by a local San Diego firm are currently switching light in 1.5 fs. (One millionth of a billionth of a second. inexpensive photographs.). photonic transistors have been produced that react to photonic signals in the time of one cycle of one wavelength of the light being used. The photonic transistor truly is the first method developed that switches light with light at the full speed of light To be precise. Visible light is a small part of the electromagnetic spectrum.Photonic Transistor: A transistor is a switch that is turned on and off by signals from other switches. it was generally thought to be impossible to switch one beam of light on and off with another beam of light. with the 1500 nm light used in fiberoptic communications switching in 5 fs. However.1 fs. . which is necessary in order to manipulate information and perform computing functions completely in the light-speed optical domain. For red light that switching time is about 2. Blue is about 1. store information and are the workhorses of digital computing. photonic transistors are not whittled out of silicon. Until the invention of the photonic transistor. Instead they are made out of photographs ie. Photonic transistors use light to perform the switching functions that are performed by electronic transistors in conventional computers. like radio waves only having carrier frequencies in the terahertz (trillion cycles per second) range rather than the megahertz range. They perform logic. Each photon provides an independent information-carrying variable for each independent photonic frequency or color. but a multi-colored beam of light is like a parallel bunch of wires where each "wire" is a different color. The 1st one on and the 2nd one off. Multiply that times the number of colors and it represents a gigantic amount of information carrying capacity. By switching the light on and off that goes through each slit independently we have produced a two-input photonic device that produces a dynamic image from which we are able to extract energy to form our outputs. Photonic Switching Many electronic-imitating Boolean logic devices. In one of the simplest arrangements. . nearly every information processing device can now be produced using light speed photonics. and Both beams off. The 2nd on and 1st off. carry over 200 terabits of information per second. in theory. . the two inputs are two slots side by side. This produces 4 different possible configurations: • • • • Both light beams on. have two inputs that at various times are either on or off. which are the basic transistor circuits used to build digital computers. Since the photonic transistor is able to manipulate those bits in the optical domain just as nimbly as electronic transistors manipulate the information in electronic circuits. So the capacity of light to carry information in serial surpasses electronics because of light's physical structure. Each color can. The entire Library of Congress has only about 30 terabits of information in it. they form an interference fringe onto a fringe component separating mask. or it will function as a boolean OR circuit if both beams are modulated.' a minima occurs over the output hole. and an XOR circuit. However. Thus. If the hole in the mask is placed at the position of constructive interference (CI). because 'light makes darkness. the device is an XOR. that in spite of the phase shift. the output is off. How we use that information depends on what is needed in . so nothing goes through the hole. the output through the hole is four times the intensity of a single beam. This introduces a phase modulation component that must be compensated for in succeeding components. (d). It is important to note though. When two laser beams are combined (a & b). the needed logic information has been extracted by a combination of its inputs. If one beam is shut off (c) the fringe goes away. If both beams are shut off.Figure:A simplified photonic transistor showing an amplifier/boolean OR circuit. The device will amplify a modulated input signal if the other beam is kept on all the time. then a boolean XOR circuit is produced. and light goes through the hole in the mask to produce an "on" output of intensity 1. the output when both inputs are on is off. The XOR: An output hole placed at the location of the minima provides an output when either of the input beams is on by itself. No energy arrives at that location. If the hole is placed at a position where destructive interference (DI) occurs (b). There is a 180-degree phase shift that occurs between the two single beam states. In Boolean computer switching logic terms. While there is a variation in output amplitude that must be compensated for. that 2nd input beam is actually turning the power beam on and off. With the NOT. the CI position? Now energy appears in the output whenever any of the beams are on. . when the 2nd input is on. no XOR information is extracted! Such steps are vital for the creation of photonic computing. without interference. this Boolean device is an OR. if one of the beams is kept on all the time. The NOT: As with any XOR. However. the output is off and vice versa.succeeding logic stages. the device becomes a NOT. and without energy separation from the components of the Dynamic Image. The OR: What happens if the hole is moved over to the maxima. That is. because the reverse phase state is not used. and the other beam causes its energy to either exit the hole or not exit the hole. there is no adverse phase modulated component. Since that one beam is kept on as a power supply to the device. These conversions are inefficient and limit the instantaneous nature of computing. will be far more valuable than their slower electronic counterparts. Current processors are reaching speeds of 1. and have a higher bandwidth than do electrons. However. A new solution is needed. Consider another example: the desktop computers that most of us use each day. expanding at almost 15% per month. Today a message is first converted fromelectronic to photonic form and then transmitted over fiber-optic cables. This is because photons (the basic unit of light) go faster. the manufacturing processes are becoming increasingly expensive for producing even minor improvements. and far less expensive to manufacture. The light signal at the other end must then be converted back into electronic form for processing by the receiving computer. Today's technology. Photonic computing uses photons of laser light to do the same job. is pushing the electron to its physical limits. Photonic computers.Approaches for Providing Solution The efficiency to be gained from using computers is increasingly limited by the physical limitations of the current computing paradigm. for example e-mail. Take. therefore. However. Are we going to need anything faster than these processors? Yes the rapid growth of the Internet. Interestingly. only thousands of times faster.2GHz. As a result. most telephone companies have been investing heavily in the global conversion from copper wire to optical fiber because light does a better job of carrying information than does electricity. electronic circuits limit network speeds toabout 50 Gigabits per second (1 Gigabit (Gb) is 109. Electronic transistors are whittled into silicon wafers to make modern computer chips. they will become the next logical computing upgrade. . photons are inherently more valuable than electrons. photons are manipulated using inexpensive computer-generated holograms made of plastic or glass. demands faster speeds and largerbandwidths than electronic circuits can provide. or 1 billion bits). however. Thus. Electronic computing uses electrons to perform the logic that makes computing work. If we can just get them to accomplish the logic tasks that make computing work. This is 79. materials exist 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.000. .463. This "optical transistor" effect is used to create logic gates which in turn are assembled into the higher level components of the computer's cpu.366. or 4. computers process information in binary units by identifying an electric charge. To accomplish this. or the absence thereof. the spatial coding. While that may seems rather fast.770.374. To replace electronic components with optical ones. an IO device in a Photonic system must first be given a specific light wave frequency range in order to communicate with the CPU (similar to how the Interrupt Request settings work in most PCs).296 bpt. We confirmed correct operation of the quantum teleportation algorithm by computer simulation. so the total output is 232 bpt.514. However.336 times more powerful than most desktop computers.228. This frequency will allow the computer to know which IO device the incoming information is from.543.ANALYSIS AND ALGORITHMS The fundamental building block of modern electronic computers is the transistor. For example. In the proposed scheme.162. an equivalent "optical transistor" is required. This allows the device to communicate directly in hexadecimal digits. In this paper. without needing to translate to binary.294. Several implementation methods of quantum computation algorithm by conventional computer have been explored for large-scale emulation.264. In particular.950. as being a “one” or a “zero. with ‘x’ being the current limit across the system bus. Currently.282.607. each representing a different hexadecimal digit. the use of Photonic computing could easily increase the rate of computing power to 16x bpt.593.000 bpt.938. quantum information is represented by the intensity and the phase of elemental cells.920. This frequency is further divided into 16 subsequent ranges.431. Due to the lack of quantum effects.” This allows the computer to calculate at a rate of 2x bpt (bits per unit time). is studied as an efficient implementation method of quantum computation algorithms.337. This is achieved using materials with a non-linear refractive index. which is an effective digital optical computing technique.967. the current limit for most desktop computers is 32 bpt. the same computer utilizing Photonic Computing Technology would output information at a rate of 1632 or 340. these methods generally require exponential growth of the size of the hardware with increase of the number of qubits.463. each at a different light frequency. The diagram below summarizes this process. The processor will then identify the incoming IO source by the photon’s frequency range. For example. . The processor can than carry on processing the information in hexadecimal digits rather than binary. The limits of computational power have yet again stretched far beyond anything previously imagined. if the device were a keyboard sending the following hexadecimal value “78AE6C. Photonic Computing not only increases the speed of data transmission. This information will then travel at the speed of light through the connecting medium (typically optic fiber) until it reaches the processing chip. and will then interpret the value of the photon by the same method. but also dramatically increases the quantity of information being transmitted. but each one being within the limits of that device.The device will then send the information to the CPU in the form of photons.” a total of 6 photons would be sent to the CPU. The organization of photonic logic stages imitates the organization of logic stages in an electronic computer because we want the photonic computer to do the same things that regular computers do. a Pentium Pro or a hand calculator.. entire computing systems are built by interconnecting millions of them in information-flow and control architectures. The basic element of a computer is the logic gate which performs the basic logical operations. the concepts of communications and information theory constitute the basis of optical information processing. information is carried on beams of light just as it is carried on a radio. or microwave signal. Boolean logic functions are easily generated by machines.only faster. From a hand full of logic operators. The basic switching functions of digital computers use Boolean logic.. indeed.Photonic Logic: Photonic computing is based on a new way of analyzing the optical problems. And the first step to understand its working is to give it an input. The result can be an IBM PC. but they all work the same. television. . Here pulse coding is used both for carrying data and for opening and closing logical gates that direct photonic information around photonic circuits. Invented by George Boole in the middle of the 19th century. Figure 2.3 – State3. Pulse reaches the gate. Figure 2. OR output pulse. the two black rectangles are the holograms that are used to create the logic here it is OR and XOR. Figure 2. XOR output pulse. .2 – State2. Pulse at input In this figure the small square at the top input is the data pulse. Pulse reaches the gate.1– State1. Holography is a process by which three-dimensional images can be stored and reproduced using laser light. hence the name. The architecture is similar to that used in electronic computer chips. fine-grained piece of photographic film. It's just faster and less expensive to manufacture. However. unlike a photograph which records an image as seen from one particular viewpoint. Also. "holography" comes from the Greek word "holos" meaning "whole" and "graphos" meaning "message. computer generated holograms have the ability to imitate nearly any ordinary optical setup. gives out laser light from its surface and has a laser cavity that is vertical. The medium that stores the image--called a hologram--is nothing more than an exposed. and offers significant advantages when compared to the edge-emitting lasers currently used in the majority of fiber optic communications devices. however. However. They emit at 850 nm and have rather low thresholds (typically a few mA).HOLOGRAMS Holograms are just one method for making photonic transistors. The complexities of optical integrated circuits can be calculated into a set of holograms that enable the light to manipulate the light in complex photonic circuits. a hologram is a record of an image as seen from many viewpoints. their laser cavities run horizontally along their length. There are two special semiconductor materials sandwiching an active layer where all the action takes place. Conventional lasers are known as ‘edge emitters’ because their laser light comes out from the edges. They can be made with optical fibers. In fact. developed." A hologram does indeed record the "whole message" of an object. But rather than reflective ends. They are very fast and can give mW of coupled power into a 50 micron core fiber and are extremely radiation hard. in a VCSEL there are several layers of partially . Some Key Photonic Components for Computing: The major breakthroughs on optical computing have been centered on the development of microoptic devices for data input. A vertical cavity surface emitting laser (VCSEL – pronounced ‘vixel’). and a host of other optical methods. VCSEL is a semiconductor vertical cavity surface emitting microlaser diode that emits light in a cylindrical beam vertically from the surface of a fabricated wafer. The principles involved in the operation of a VCSEL are very similar to those of regular lasers. and image processing and compression. Hence by being able to individually program the memory locations one can set up a pattern of optical activity in the liquid crystal layer. The purpose is to leverage the advantages of each individual technology and provide improved performance for specific applications. an optical computer is a computer in which light is used somewhere. Smart pixels. both expands the capabilities of electronic systems and enables optical systems with high levels of electronic signal processing. Here. Broadly speaking. Another advantage of light results because photons are uncharged and do not interact with one another as readily as electrons. free space connections. Thus. For such purposes designing silicon chips for use as spatial light modulators has been effective. The voltage between individual mirrors and the front electrode affects the optical activity of the liquid crystal in that neighbourhood. Smart pixel technology is a relatively new approach to integrating electronic circuitry and optoelectronic devices in a common framework. for inputting information on light beams. light beams may pass through one another in full duplex operation. for example without distorting the information carried. Spatial light modulators (SLMs) play an important role in several technical areas where the control of light on a pixel-by pixel basis is a key element. The basic idea is to have a set of memory cells laid out on a regular grid. . the electronic circuitry provides complex functionality and programmability while the optoelectronic devices provide high-speed switching and compatibility with existing optical media. This can means fiber optical connections between electronic components. the digital optical computers will be based on photons. and each mirror reflects a narrow range of wavelengths back into the cavity in order to cause light emission at just one wavelength. or one in which light functions as a mechanism for storage of data. and value is added to optical systems through electronic enhancements which include gain feedback control. Layers of semiconductor with differing compositions create these mirrors.reflective mirrors above and below the active layer. A layer of optically active liquid crystal is sandwiched between this array of mirrors and a piece of glass with a conductive coating. such as optical processing. Instead of electrons in silicon integrated circuits. such that the voltage on the mirror depends on the value stored in the memory cell. and displays. smart pixel systems add value to electronics through optical input/output and interconnection. the union of optics and electronics. Consequently. These cells are electrically connected to metal mirrors. logic or arithmetic. For display purposes the desire is to have as many pixels as possible in as small and cheap a device as possible. but the pace of research and development has increased through the 1990s. In the case of electronics. for example without distorting the information carried. and optical spectrum analyzers. Since photons are uncharged and do not interact with one another as readily as electrons. optical materials possess superior storage density and accessibility over magnetic materials. a great deal of effort has been expended in the development of digital optical processors. light beams may pass through one another in full-duplex operation.Uses of Optics in Computing: Currently. Development of optical processors for asynchronous transfer mode. much progress has been achieved. high frequency or fast switching pulses will cause interference in neighbouring wires. For example. On the other hand. and optical signal processors have been successfully used. In the past two decades. there has been continuing emphasis on the following aspects of optical computing: Optical tunnel devices are under continuous development varying from small caliber endoscopes to character recognition systems with multiple type capability. capable of processing large amounts of data in parallel. . fingerprint enhancement. Further. Laser diodes as sources of coherent light have dropped rapidly in price due to mass production. The field of optical computing is progressing rapidly and shows many dramatic opportunities for overcoming the limitations described earlier for current electronic computers. Development architectures for optical neural networks. optical image processing. however. optical pattern recognition. Development of high accuracy analog optical processors. loops usually generate noise voltage spikes whenever the electromagnetic fields through the loop changes. The early work in optical signal processing and computing was basically analog in nature. signals in adjacent optical fibers or in optical integrated channels do not affect one another nor do they pick up noise due to loops. The process is already underway whereby optical devices have been incorporated into many computing systems. Much work remains before digital optical computers will be widely available commercially. for applications such as synthetic aperture radars. During the last decade. optics is used mostly to link portions of computers. Finally. or more intrinsically in devices that have some optical application or component. Finally. which is implemented by optical disks or by holographic storage systems. without observable or measurable generation of unwanted signals. for example the use of free-space optical interconnects as a potential solution to alleviate bottlenecks experienced in electronic architectures. These devices are used to write data into the optical storage medium at high speed. This high bandwidth capability offers a great deal of architectural advantage and flexibility. including loss of communication efficiency in multiprocessors and difficulty of scaling down the IC technology to sub-micron levels. and even intersect. The SLMs and the linear array beam steerer are used in optical data storage applications. Light beams can travel very close to each other. and low-cost data storage devices necessary for future intelligent spacecraft. low-power. as light travels fast and it has extremely large spatial bandwidth and physical channel density. this could be further increased to 1000Tbits. as light is immune to electromagnetic interferences. risk of noise is further reduced. high-capacity. rapid. In addition. Current trends in photonic computing emphasize communications. Free-space optical techniques are also used in scalable crossbar systems. The primary benefits offered by holographic optical data storage over current storage technologies include significantly higher storage capacities and faster read-out rates. This type of memory promises very high capacity and storage density. dense arrays of interconnects can be built using optical systems. entertainment and data storage companies are looking at ways to increase the amount of stored data and reduce the time it takes to get that data out of storage. In optical computing two types of memory are discussed. as well as to massive-capacity and fastaccess terrestrial data archives. As multimedia applications and services become more and more prevalent. optical CD-ROM discs are now very common in home and office computers. radiation-resistant. Therefore. Optical sorting and optical crossbar inter-connects are used in asynchronous transfer modes or packet routing and in shared memory multiprocessor systems. it appears to be an excellent media for information transport and hence can be harnessed for data processing. The analog nature of these devices means that data . future systems could have 1024 smart pixels per chip with each channel clocked at 200MHz (a chip I/O of 200Gbits per second).and random-access. which allow arbitrary interconnections between a set of inputs and a set of outputs. giving aggregate data capacity in the parallel optical highway of more that 200Tbits per second. This research is expected to lead to compact. One consists of arrays of one-bit-store elements and the other is mass storage.Also. Based on the technology now available. Thus resulting in cheaper ICs and this is due to the fact that only a small amount of silicon is needed for a photonic computer. And the goal of the research is not only achieving high performance in silicon photonics. but doing so at a price point that makes the technology a natural fit – even an automatic feature – for all devices that consume bandwidth. And if the level of connections between the components inside the chip is greater then computer generated hologram would bring the solution to this problem. ADVANTAGES Low prices The silicon photonics is an attempt to make the silicon based integrated chip (IC) smaller and yet remain efficient.can be stored at much higher density than data written by conventional devices. . Less heating Over heating is the problem that is faced when the processor works more than normal operation speed that is when it is over clocked. These kind of systems are ideal for image processing. Interconnections made easier Visible-light and IR beams. micron-scale photonic crystal chip the size of the devices which use this principle gets more reduced thus making it work for network devices(Optical network). Otherwise considerable noise will be introduced into the system. systems for complex mathematical calculations. More Multi processing. but there is no interference .Low size The size of the photonic ICs is very less. easily manufactured. By integrating multiple optical functions on a single. is able to operate using pipelined pulses. the input must remain either completely on or completely off for that full nanosecond. but I photonic ICs this is not a problem as they use very less amount of energy and photons which are running inside the ICs for communications are generated by low power laser. if the transit time through an electronic transistor is one nanosecond. pulses that are much shorter than the transit time of the device. unlike electric currents. The Photonic transistor. however. As the integration becomes easier and denser in size it increases the efficiency of the computers by providing more cache memory. pass through each other without interacting. and they will all be processed independently without any noise buildup. Several (or many) laser beams can be shone so their paths intersect. servers which have so many processors. threads in the different processors in the same processor chip. it leads to more level of multiprocessing than is present in our latest processors. As the Photonic ICs are ideal for multi core architecture to produce processors with more options fro running more processes. a continuous stream of very short pulses can be introduced into a single transistor. That is. Parallel computing It supports parallel computing as the photonic transistors provides pipelined pulses. retrieve and process data. might also be smaller. even when they are confined essentially to two dimensions. Thus. an optical computer. Another key benefit of the photonic computer is that less energy is used to power the system and it does not have the same interference problems that make it difficult for current chip manufacturers to make smaller transistors. Although this system is complete. First. Connections in electric and optical circuits. the only way to upgrade the operating system is to get a new processing . and this makes three-dimensional wiring are necessary. The processor itself is a laser inscribed piece of crystal made in the laboratory. This is because light energy does not interact with other photons. This means that the computer itself is not susceptable to computer viruses that effect operating systems. Conclusion The Photonic Computer uses only light to collect. The Photonic Computer is also different from a traditional computer in many other ways. besides being much faster than an electronic one. it is still very simple and not very useful. and the current system uses only a huge amount of RAM to store information. because information and processing occurs at the speed of light. Second.among the beams. the hardwired operating system is laser etched into the crystal. This makes it operate much faster than electronically based computers. Electric currents must be guided around each other. Future Scope Beyond the photonic/electronic computers are quantum computers. a hundred particles could execute a computation on 2100 numbers in parallel. (In this field. at least. In a quantum computer. thus far. the term "bit" is replaced by "qubit. as it implies a unified scientific and technological field of . making it possible for each particle in a quantum computer to hold more than one bit of information. Optical data storage devices will also be important in the development of optical computers. which use the properties of quantum mechanics to process data at incredibly high speeds. In the near term. for instance. information is stored not as a string of ones and zeroes. Researchers have already designed and built alloptical logic gate circuits for dataprocessing at Gigabit and Terabit rates. only a hypothetical machine. Algorithms have been created that use this parallelism and allow a quantum computer to make lightningfast searches through a database. say. Optical connections within electronic computer systems will speed data between the parts of a computer and optical switches will mix in with electronic processors to move information quickly without generating the heat that comes off copper wires.crystal." meaning quantum bit. A quantum computer is.) A computer containing. or polarization orientations of a photon. but as a series of quantum-mechanical states: spin directions of electrons. Quantum physical law allows particles to be in more than one state at a time. Nanophotonics. Photonic computers will most likely be hybrid optical/electronic systems that use electronic circuits to preprocess input data for computation and to post-process output data for error correction before outputting the results. They are expected to become reality between 2030 and 2050. Technologies currently underinvestigation include advanced optical CD-ROMs as well as Write/Read/Erase optical memory technologies. either in fiber-optic communications or inter / intra chip optical interconnects in computing systems. it is apparently light (or photons) that carries information through communication systems. therefore. and chip testing. The diffraction limit. metallic interconnects will eventually be a bottleneck that would impose serious limitations on computing performance. nanophotonics. is an emerging field of study built upon modern science and advanced technologies. Maier et al. discussed an ultimate route to nanoscale optical devices that would not be constrained by the diffraction limit by introducing the term plasmonics. Neither photonic bandgap crystals nor silicon nanophotonic devices described earlier overcome the diffraction limit associated with a specific wavelength that needs to be used. inter-board) become apparent i. For ultimate integration of nanophotonic devices. SILICON NANOPHOTONIC DEVICES Silicon is the material that has been driving microelectronics in the past several decades. eventually draw the upper-bound of the level at which the overall size of a discrete device or an integrated photonic circuit can eventually be scaled down. the key is. interchip. greater data transmission distance. chip fabrication process packaging. OPTICAL NEAR-FIELD NANOPHOTONIC DEVICES The "diffraction limit" notoriously imposes a clear physical limit on how we handle propagating electromagnetic waves. silicon nanophonics that can be integrated on silicon CMOS platforms would allow future computing systems to have smaller size. higher data rate. it is certainly natural to seek practical solutions to numerous road-blocks on the way towards further advancement within a framework of silicon CMOS technologies. In the past several years. lower power consumption.nanotechnology and photonics. Given a large amount of capital invested on CMOS technologies that include chip design / architecture. has been rather used with a variety of definitions preferably found within a wide range of technical fields. .. Furthermore. to find a way to guideb electromagnetic waves (or energy) within a scale below the diffraction limit. The term.e. Complementary metal semiconductor oxide (CMOS) technology based on silicon has always been on the main stream of discussion and development in microelectronics. Silicon nanophonics would offer a route to add various photonic functions that are compatible with mature CMOS platforms. the field of silicon nanophotonics has been gaining significant attention as challenging technical issues associated with current metallic interconnects (intra-chip. When nanophotonics is viewed in a framework of establishing communications based on photons. and more functions. of course. The term will likely to find itself in variety of fields ranging from bioscience to advanced solid-state devices. I/Oof 2. low latency memory access for the processors. We have optimized all three interconnection types not only for high bandwidth and low latency but also for power efficiency.5 TBps (to disks orusers). a system bisection bandwidth of 1 B/flop (or 10 TBps). This design uses three types of interconnects: high bandwidth.BENEFITS OF THE SILICON PHOTONIC MICROSYSTEM The proposed macrochip design (requires a DRAM bandwidth of 640 GBps per site. massive. and additional scalable off-macrochip bandwidth for node-to-node fiber interconnects. high-density messagepassing on the macrochip among processors. . and offmacrochip I/O for node-to-node interconnects. an aggregated bandwidth of 20 TBps.