OBJECTIVE

To study the laser beam characteristics like

angular divergence and aperture.

Laser History•1917 -Albert Einstein: Theoretical prediction of stimulated emission

•1946 -G. Meyer-Schwickerather: first eye surgery with light

•1950 -Arthur Schawlow and Charles Townes: Emitted photons may be in the visible

range

•1954 -N.G. Basow , A.M. Prochorow , and C. Townes: ammonia maser

•1960 -Theodore Maiman: firstlaser (ruby laser)

•1964 -Basow, Prochorow, Townes (Nobel prize): quantum electronics

•1970 -Arthur Ashkin: laser tweezers

•1971 –DénesGábor (Nobel prize): holography

•1997 -S. Chu, W.D. Phillips and C. Cohen-Tanoudji (Nobel prize): Atom cooling with

laser

• A Laser source (0.5m W)

• Optical bench

• Screen.

APPARATUS

The divergence tells us how rapidly

the beam separates when it is

emitted

from the laser. Although the

divergence angel can be measure in

fractions of degrees or radian,

the relation between degree and

radian is

2π = 360 degree

and 1 radian= 57.3 degree,

DIVERGENCE

Laser beam slightly diverges due to diffraction

phenomenon. Hence it is characterized by

extremely low divergence. But, when the beam

propagates outward, it slowly diverges . For an

electromagnetic beam, beam divergence is the

angular measure of the increase in the radius or

diameter with distance from the optical aperture

as the beam emerges.

When a laser beam is allowed to fall on a

screen then a circular bright spot is observed

on the screen

PHENOMENA DUE TO WHICH

LASER LIGHT DIVERGE

THEORY:Ordinary light sources emit light in all directions because an

ordinary light is non- directional in nature and intensity of this light

decreases with increasing distance. Laser beam is directional in

nature because of which the intensity of light is very large.

Laser beam slightly diverges due to diffraction phenomenon.

Hence it is characterized by extremely low divergence. But, when

the beam propagates outward, it slowly diverges . For an

electromagnetic beam, beam divergence is the angular measure

of the increase in the radius or diameter with distance from the

optical aperture as the beam emerges.

When a laser beam is allowed to fall on a screen then a circular

bright spot is observed on the screen and if screen is moved

towards the source then size of the spot decreases and if screen

is moved away from the source then size of the spot increases.

We can calculate the divergence of a beam if the beam diameters

at two separate positions (1, 2), and the distance (L) between

these positions are known.

Laser

source

Screen Screen

L

DIAGRAM

LASER SOURCE

A laser is a device that emits light

through a process of optical

amplification based on the

stimulated emission of electromagnetic

radiation. The term "laser" originated as

an

acronym for “Light Amplification by

Stimulated

Emission of Radiation".

Lasers differ from other sources of light

S.NO. D1 D2 L Θ= (√(D2.D2-

D1.D1)/L)180/

π

1 4 8 512.5 .07

2 5 8 511 .79

3 5 8 461 .94

OBSERVATIONS AND CALCULATIONS

(0.07+0.79+0.94)/3 = 0.6 degree

RESULTThe angular divergence of laser beam is 0.6 degree

REFRENCES

•

http://www.infoplease.com/encyclopedia/science/laser-

characteristics-lasers.html

•

http://physics.stackexchange.com/questions/79417/why-

does-a-laser-beam-diverge

• http://www.worldoflasers.com/laserhistory.htm

• http://www.infoplease.com/encyclopedia/science/laser-

characteristics-lasers.html

• Text books

• Lab manuals

GROUP MEMBERS