11.1  ELECTRO MAGNETIC WAVES

• Electromagnetic waves are used to transmit long, short, frequent wavelength radio waves and TV/ Telephone / wireless signals or energies. They are also responsible for transmitting energy in the form of microwave, Infra-red, visible light, UV, X rays , gamma rays
• Radio waves ® Radio waves are emitted by stars in space
• Microwave ® Microwaves are used in micro wave oven & Microwaves in space are used by astranauts to study the structure or nearly galaxies and Milky
• Infra-red ® our skin emits IR. In space IR maps dust between stars
• Visible light– fire flies and light bulbs emit visible light
• UV – Sun and stars emit UV rays
• x- ray ® Not gases in universe x rays
• gamma ® Radioactive (natural and manmade)
• Universe emits gamma rays

11.2      ELECTRO MAGNETIC SPECTRUM

• Electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The Electron magnetic spectrum extends from low frequencies used for modern radio communication to gamma radiation there by covering wavelength from 100s of kilometre down to a fraction of the size of an atom

11.3        FIBRE OPTICS

• It is a form of transmission system in which very thin glass and special plastic fibres are used to transmit light waves through out their length (by the methods of total internal reflection). Such light waves of higher band width can carry 2500 calls at a times
• It is the science of transmitting data voice and images by the passage of light through thin transparent fibres or some other material of high refractive index
• Fibre optics replaced copper wires in long distance telephone lines and used to link computer within LAN
• Optical fibre is flexible, transparent Fibre made of glass (silica ) or plastic. Slightly thicker than human hair. It functions as a wave guide or light pipe to transmit light between the two ends of a fire

Advantages :

• Unaffected by electromagnetic induction
• Noise free
• Freedom form cross talks
• Safe from short circuit
• Unaffected by high pressure and heat
• Can over long distance

Applications:

• Image transmission by optical fibres is widely used in medical instrument like endoscopes for viewing inside the human body and for laser surgery. Industrial endoscope are used for inspecting anything hard to reach such as jet engine interiors.

• Optical fibres are also being used in variety of sensing  devices from thermometer to gyroscope Fibres have also been developed to carry high power laser beams for cutting and Drilling
• Fibre optic laser system are used in communication networks for transcontinental and undersea cables are in operation and in LANs.

11.4      LASER

• Laser – Light amplification by stimulated emission of radiation.
• A laser is a device that emits light (electromagnetic radiation) through a process of optical  amplification based on the stimulated emission of photons. It produces a thin intense beam of light which is highly coherent.

Types :

• Gas laser – Many gas discharges have found to amplify light coherently e. Co2. Red HeNe laser by used for industrial and scientific
• Chemical laser – Chemical lasers are powered by a chemical reaction permitting a large am of energy to be released quickly (defence and industrial applns ) e.g        H2    flouride    laser    and deuterium flouride laser.
• Exismer laser : Excimer lasers are a special sort of gas laser powered by an electrical discharge in which the lasing medium in excimer.

Solid state lasers :

• Use a crystalline or glass rod which is doped with ions that provide the required energy states. Eg. Ruby laser ® used in tattoo and hair removal

Fibre laser :

• Solid state laser or laser amplifier where the light is guided due to the total internal reflection in a single mode optical fibre are called fiber lasers.
• Fibre lasers have their own application in telecommunication, medicine, spectroscopy – study of the interaction between matter and radiated energy

Semi conductor laser :

• Semi conductor lasers are diodes which are e-cally pumped. The development of a silicon laser is important in the field of optical computing. Silicon is the material of choice for ICs and so electronic and silicon photonic components could be fabricated on the same chip.

Bio Laser :

• Living cells can be genetically engineered to produce GFP (Green flourscent protein) GFP gain medium for amplifying light.  Two  mirrors  were  placed 20  millionths  of  a  meter  across and  when  blue  light  is  passed  it emits green light.
• Applications: Improved microscopic imaging and light based therapies.

Applications:

• Laser is useful in recording, storing and transmitting information and they can also be used in scanning heating measuring and guiding. As a result of their wide use lasers can be found in equipment used in homes,  factories,    offices, hospital and libraries.

Some of the major applications are listed below

• The most common use of laser include the recording of music, motion picture complete data in CD/ DVD
• Laser can also read and play back the information recorded on discs
• Laser beams can produce 3D images in a photographic process called Holography method for storing and displacing a 3 D image usually on a photographic plate or another light sensitive material.
• Laser is used in the field to fibre optical communication that changes eliectrical signals of telephone calls and TV pictures into pulses of laser light
• Laser scanner are used in supermarkets to scan the bar codes of consumer goods and also in libraries to keep track of books and in post offices to sort mails and to read a/c no an cheques in banks
• Laser light shown are conducted with scanning laser beams
• Industrial laser are used to cut and weld metals. Drill holes and cut ceramics, cloth and plastics as laser beams produce great amt of heat
• In the field of medicine, heating power of laser is often used in eye surgery to close off broken blood vessels on the retina and to detach a loose retina. Laser beams can replace surgical  knife in some operation which permits extra ordinary control and precision in cutting tissue and sealing off cuts. It reduces bleeding damage to nearby healthy tissue.
• In nuclear energy research scientist use laser to produce controlled miniature

H2 bombexplosion

• Lasers are also used to measure distance.Laser devices used to measure shorter distance are called range   finders surveyors(Use the devices to get information needed to make maps) Military personal use them to calculate the distance to an enemy
• Instruments called laser gyroscope use laser beam to detect changes in direction. These devices help ships, airplanes and guided missiles to stay on Course

11.5       MASER

• A maser is a device that produces coherent electromagnetic waves through  amplification   by stimulated emission MASER – Microwave amplification by stimulated emission of radiation

Types :

• Atomic beam maser e.g: Ammonia maser, free electron maser, H2
• gas maser e.g: Rublidium maser
• Solid state maser e.g. : Ruby

Applications :

• Maser serve as high precision frequent references. These atomic frequency standards are one of the many forms of atomic clocks.
• They are used as low noise microware amplifier in radio telescope.
• They are used as directed energy weapon( emits energy in an armed direction without any projectile.It transfers energy to a target for a desired )

11.6      OPTICAL COMPUTING

• Computers use movement of electrons in and out of transistors to do logic. Optical or photonic computing is intended to use photons or light particles produced by laser or diodes in the place of electron. Compared to electrons, photons are much faster.   Light travels about 30 m or  1  foot  in  a  nano  second  and have higher bandwidth .

• Single high tech components are available but no optical
• Today’s optical computers are only prototypes do not reflect the whole capabilities of optical computing.

Advantage: (theoretical advantage)

Higher performance:

• The most significant advantage of optical computers is the potential of higher
• Light and photons are perfect information carriers. Even long distance can be bridged within split second. Fully optical RAM, bus systems using laser to communicate, optical processers and holographic devices would be much faster than electronic ones.

Higher parallelism :

• Optical computers can be built with higher bandwidth. Within one datapath several data sets can be transmitted parallelly at the same time using different wavelength. Data paths can cross each other without interference and the layout can be 3 dimensional. This allows for higher        paraIIelism                        (but architecture and operating system should be adjusted)

Less power consumption:

• OCs have the potential to be more power saving as friction between integrated chips do not occur when light is used as information carrier.

Less heat is released:

• In Optical cables laser can be used as light sources. Those concentrated light beams only consist of a small spectrum of different wave

Less noise:

• Optical cables could be absolutely noiseless as no fan will be needed. Laser can be cooled with passive coolers and heat pipes built out of aluminium and copper.

Less loss in communication:

• Data sent through wires need to be amplified several times to bridge longer distance the communication with optical fibres is almost lossless due to TIR

Less wear tear

• Wear and learn normally occurs at mechanically moving parts. In conventional computers, fan, hard disk drives, removal storage disk, rotate and move very fast which causes fruition and wears out.

Move flexibility in layout

• For the speed of electronic connection which depends on the length of the cables and pipelines. Conventional PCs are built as rectangular box or laptop on the mother board, CPU, RAM, Graphics card have to be closer to each other to be able to move large amts of data. But for optical components, distance of communication doesn’t matter. So the technology has the potential to change the shape and layout of computer