laser beam characteristics

laser beam characteristics

1. LASERS

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 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

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

5. 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

6. 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

7. 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 .  

8. Laser source Screen Screen L DIAGRAM

9. 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 because they emit light coherent.

10. 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

11. 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

12. GROUP MEMBERS B130010328 B130010326 B130010327 Rahul Pathania Gurprasad Singh Archu Sood