MAIN FEATURES OF A MAIN FEATURES OF A LASERLASER

DIRECTIONALITYDIRECTIONALITY INTENSITYINTENSITYMONOCHROMATICITYMONOCHROMATICITYCOHERENCECOHERENCE

PRINCIPLE OF LASER ACTIONPRINCIPLE OF LASER ACTION

SPONTANEOUS EMISSIONSPONTANEOUS EMISSION

STIMULATED EMISSIONSTIMULATED EMISSION POPULATION INVERSIONPOPULATION INVERSION

SPONTANEOUS EMISSIONSPONTANEOUS EMISSION

STIMULATED EMISSIONSTIMULATED EMISSION

POPULATION INVERSIONPOPULATION INVERSION

In some materials in which the atom is in metastable In some materials in which the atom is in metastable state, it is possible to have more number of atoms in state, it is possible to have more number of atoms in metastable state than in lower state. (i.e., Nmetastable state than in lower state. (i.e., N22>N>N11))

CONDITION FOR LASER ACTIONCONDITION FOR LASER ACTION

Active material in which population Active material in which population inversion can be attained.inversion can be attained.

A specially cylindrical tube fitted with A specially cylindrical tube fitted with mirrors . One is completely silvered and mirrors . One is completely silvered and other is partially silvered.other is partially silvered.

Pumping system – to achieve population Pumping system – to achieve population inversion.inversion.

TYPES OF LASERSTYPES OF LASERS

SOLID TYPE LASERS SOLID TYPE LASERS SEMI-CONDUCTOR LASERSSEMI-CONDUCTOR LASERSGAS LASERSGAS LASERS

SOLID LASERSSOLID LASERS -Ruby laser-Ruby laser

SEMICONDUCTOR SEMICONDUCTOR LASERSLASERS

-Gallium-Arsenide Laser-Gallium-Arsenide Laser

GAS LASERSGAS LASERS

-He-Ne laser-He-Ne laser

APPLICATIONS APPLICATIONS

Measurement of distancesMeasurement of distancesCommunicationCommunicationMaterial ProcessingMaterial ProcessingMedical ScienceMedical ScienceDefenseDefenseTechnologyTechnology