laser beam characteristics

2. OBJECTIVE
To study the laser beam characteristics like
angular divergence and aperture.

3. 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 visi
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 w
laser

4. • A Laser source (0.5m W)
• Optical bench
• Screen.
APPARATUS

6. 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
DIVERGENCE

8. 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

9. 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

10. Laser
source
ScreenScreen
L
DIAGRAM

11. 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".

12. 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
RESULT
The angular divergence of laser beam is 0.6 degree

13. 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

14. GROUP MEMBERS