LASER

• LASER stands for light Amplification by stimulation emission of radiation.

• It produced an intense, monochromatic and unidirectional beam of light.

LASER

• In 1917, Albert Einstein first theorized about the process which makes lasers possible called "Stimulated Emission."

WORKING

Involve two most important terms:• Stimulated emission.• Populated inversion.

ABSORPTION • Consider a sample of free atoms which are in ground

state with energy E1. The incident photon is absorbed by an atom and excite to state E2.

SPONTANEOUS EMISSION:

The exited atom may decays by spontaneous mission by emitting a photon of energy hf=E2-E1.

STIMULATED EMISSION:

The excited atom decays by stimulated emission. In this case, the photon of energy hf=E2-E1 induced the atom to decay by emitting a photon of same energy , going in same direction.

SPONTANEOUS VS STIMULATED

Many wavelengths

Multidirectional

Incoherent

Monochromatic

Directional

Coherent

RESULT • Thus, we obtain an intense, unidirectional beam, by stimulated

emission. For proper working there would more stimulated emission the spontaneous emission.

POPULATION INVERSION

Let us consider a simple of material whose atoms can reside in three state:

• E1 ground state

• E2 called metastable state (reside for 10 ³ sec)⁻

• E3 is excited state (reside for 10 sec)⁻⁷

• Photons of energy hf=E3-E1 raised the atom to excited state E3 from ground state E1.

• The excited atoms dose no decay back to E1 but the atom decay to E2.

POPULATION INVERSION

• The atom reached state E2 much faster then they leave state E2.

• In this situation, the state E2 contain more atom then E1 . This situation is called population inversion.

POPULATION INVERSION

EMITTING LIGHT

• The emitted photons must be confined, this is achieved by using mirror at two end. One end is made totally reflected and the other end is partially transparent to allow the laser beam to escape.

TYPES OF LASERS• Solid state Lasers

• Gas Lasers(He-Ne laser)

• Liquid lasers

• Semiconducting lasers

• Dye lasers

LASERS IN DIFFERENT FIELDS• MEDICAL

• SCIENTIFIC

• INDUSTRIAL & COMMERCIAL

• COMMUNICATION

• MILITARY

• OTHERS

MEDICALDermatology

Tattoo

Surgery

SCIENTIFIC

• Make different type of instruments like Endoscope.

INDUSTRIAL

• Laser Welding • Laser Cutting • Laser Trimming

COMMUNICATIONBarcode readers

Laser pointers

Optical Fibers

Laser printer

COMMUNICATION

ATM Machine

MILITARY

Use in Gun Target designator

AGRICULTURE

Land Leveling using LASER.

COMMON LASER SIGNS AND LABELS