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LLight

AAmplification by

SStimulated

EEmission of

RRadiationIt was Invented in 1958 by Charles Townes and Arthur Schawlow of Bell Laboratories.

LASER PRINCIPLELASER PRINCIPLE

11) Pumping(excitation of atoms)

2) Stimulated emission of atoms

3) The lasing processis enriched by multiple reflections between mirrors

4) A laser beam exits.

amount of energy (E) is determined by the formula (first given by Einstein): E = hv The proportionality constant is Planck's constant (h): h = 6.626*10-34 [Joule-sec]

• MonochromaticThe light emitted from a laser is monochromatic, that

is, it is of one wavelength (color). In contrast, ordinary white light is a combination of many different wavelengths (colors).

• Directional: Lasers emit light that

is highly directional. Laser light is emitted as a relatively narrow beam in a specific direction. Ordinary light, such as coming from the sun, a light bulb, or a candle, is emitted in many directions away from the source.

• Coherent:The light from a

laser is said to be coherent, which means the wavelengths of the laser light are in phase in space and time.

λ is the wavelength c/f; Δφ is the part of the phase delay ,N is the integer number of wave half-cycles of the round-trip and ΔN the remaining fractional part.

At present, the submarines have to rely on a sonar to find the enemy crafts and to avoid the underwater objects. This has serious limitations: The whales, dolphins and other marine life give false signals. A typical sonar cannot give a well-defined picture because the sonar beam is broadened or scattered by sea water. A difference in the saltiness of water can cause the sonar beam to bend and make the target appear where it is not.It gives a way to the enemy the position of the shipfrom which it is transmitted..

The range can be found in the same way used in laser range finders . With high power release of several megawatts power, underwater ranging is possible up to 500 m in clear water.

It is an accurate pointing system which provides the pulsed laser sourceand the precision optics and stabilisation required to accurately shine a laser beam on a target.Laser Guided Weapon (LGW): generates an electric signal (photons converted into electrons) when laser light is received at the wavelength and with the pulse coding of the LTD system, consequently a portion of the laser light reflecting off of the target is “visible” to the weapon. This provides signals on which the LGW can “home” toward the target by actuating its aerodynamic surfaces.

There are two main categories of attacks with LTD/LGW can be distinguished:Self Designation Attacks: in which the aircraft acts as illuminator for the own carried LGW and laser illumination is automatically controlled by the LTD. The LGW is controlled by the Weapon by the aircraft computers.

Co-operative Designation Attacks: in which a ground Forward Air Controller (FAC) (or an aircraft) performs illumination with an LTD and LGW carried by an(other) aircraft.

Using target designators and guided weapons are also called smart bombs.

Laser radars are commonly referred to as LADAR for laser radar or as LIDAR for light detection and ranging.Angular information is obtained from the beam-pointing direction. Laser radars are capable of extremely accurate angular measurement because of the small beam diameters of lasers (on transmit) and narrow fields of view (on receive). On the negative side, the detection and tracking ranges are much shorter than microwave radar because of lower transmitter power and higher atmospheric attenuation.

).

Possible airborne LADAR applications:• Aircraft guidance (obstacle avoidance and terrain following);• Tactical imaging systems (surveillance and reconnaissance); and• Wind velocity measurement (clear air turbulence and severe storm sensors).

When laser first invented it was described

as “a solution looking for a problem” .

Laser rangefinders are devices to

measure the distances both inland and in

the water with civil and military

applications.

The invention of the laser is an example

of how basic research, which may begin

with no specific technology can lead to

important discoveries and life-changing

inventions.