OPTICAL COMPUTERS By Nirmal Ra J Abhishek B

OPTICAL COMPUTERS By, Nirmal Ra. J Abhishek B Mane Under The Guidance of Asst. Prof. Nelanjana Bowmick

What is Optical Computer… v An optical computer is a computer that uses photons in visible light or IR beams to perform digital computation.

EXAMPLES Consider E-mail . txt format Electronic To Photonic Converter Fiber optic cables Optical Computers perform computations, operate, store and transmit data using only light. 5

Why Optical Computers. . . ? v v v In silicon computers, the speed of computers was achieved by miniaturizing electronic components. It is also estimated that the number of transistor switches that can be put onto a chip doubles every 18 months. So further miniaturization of size introduces several problems such as dielectric breakdown, hot carriers, and short channel effects etc.

Advantages. . . v v v v v Increase in the speed of computation. Immune to electromagnetic interference. Free from electrical short circuits. Have low-loss transmission and large bandwidth. Speed of light in photonic circuits will be close to speed of light in vacuum Capable of communicating several channels in parallel without interference. Possesses superior storage density and accessibility No power loss due to excess of heating. Life of the hardware of optical computer is more.

Parallel communication

Optical computation ? v v v Light in the place of Electron Uses optical components Transistors, logical gates etc. are simulated using optics. All-optical components require a high level of laser power to function as required. Send pulses of light instead of pulses of electricity

Optical Components. . . v v VCSEL-vertical cavity surface emitting micro laser VCSELs have high performance and low cost advantages Emits light in a cylindrical beam vertically from the surface of a fabricated wafer Low-cost potential because the devices are completed and tested at the wafer level

Optical interconnection of circuit using VCSEL and photodiodes v VCSEL converts the electrical signal to optical using lens and micromirrors

v v Photonic Crystals- crystals designed to replace transistors in optical computers. Optical nanostructures that are designed to affect the motion of Photons.

v v SLMs - Spatial light modulators , play an important role in optical processing, for inputting information on light beams, and displays. A set of memory cells laid out on a regular grid and value in each cell contribute to manipulate the behaviour of optical activity.

Logical Gates – Logic gates are the building blocks of any digital system. An optical logic gate is a switch that controls one light beam with another. It is "on" when the device transmits light, and "off" when it blocks the light.

v v Smart pixels -Smart pixels, the union of optics and electronics Expands the capabilities of electronic systems and enables optical systems with high levels of electronic signal processing. Some examples LED- Light emitting diode with FET- Field effect transistor.

Use of Optics in computing. . Use of optics in intercommunication – v v v Here optical fibres are used communicate internally like communicating with peripherals etc. the use of free-space optical interconnects as a potential solution to alleviate bottlenecks experienced in electronic. Optical sorting and optical crossbar interconnects are used in asynchronous transfer modes.

Few Examples

Use of optics in Memory storagev v Mass storage, which is implemented by optical disks or by holographic storage systems. The primary benefits offered by holographic optical data storage over current storage technologies include significantly higher storage capacities and faster read-out rates. A holographic memory can store data in the form of a hologram within a crystal. The analog nature of these devices means that data can be stored at much higher density than data written by conventional devices.

Process of Memory Storage using Optical Computing

Current work and Improvements. By NASA v The thin films being developed. v Can perform switching, signal processing and frequency doubling v NASA have developed and built all-optical logic gate circuits for data processing THIN FILM TRANSISTOR

By IBM v v IBM announced that its researchers have built a device capable of delaying the flow of light on a silicon chip, a requirement to one day allow computers to utilize optical communications to achieve better performance. Almaden Research Center at IBM have developed ultrafast data storage devices that use laser pulses

At the University of Bristol in the UK v Researchers have made a prototype optical quantum computer chip and used it to perform a mathematical calculation for the first time. Intel claims optical computing "milestone“ v Intel's hybrid silicon laser research has allowed it to transfer 50 Gb/s down a single fibre-optic channel. Intel has made a breakthrough in optical connection technology with the world's first endto-end silicon photonics connection, which the company claims "could revolutionise computer design, dramatically increase performance, [and] save energy. "

Challenges. . . Finding materials that can be mass produced v Practical limits of eight to eleven bits of accuracy-intensity fluctuations. v Computation is a nonlinear process in which multiple signals must interact to compute the answer. v Making photonic crystals is a difficult process. v Putting optical switches on computer chips. v Fabrication. v

The Smallest Laser Ever Made v Surface-plasmon lasers could enable a new generation of computers based on nanophotonics

DRAWBACKS v Today’s materials require much high power to work in consumer products, coming up with the right materials may take five years or more. v Optical computing using a coherent source 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.

CONCLUSION Optical technology promises massive upgrades in the efficiency and speed of computers, as well as significant shrinkage in their size and cost. v Even though pure Optical computer has many challenges hybrid opto-electrical computer can be expected very soon, and in near future pure optical computer too. . v

Thank You

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