Laser And its Application's - Engineering Physics

This PPT has covered,
1)Principle of Laser
2) Types of Laser
3)Application Of Laser

1. LASER and its applications

2. Outline:- Introduction Basic processes Types of Laser Ruby Laser He-Ne Laser Application of LASER

3. LASER An acronym LASER is used for Light Amplification by Stimulated Emission of Radiation . Due to some unique properties laser beam is superior as compared to other light sources. Highly Monochromatic Highly Directional Coherence High intense Characteristics of LASER

4. Stimulated Absorption If the photon of energy is incident on the atom in the lower energy state, the atom absorbs the incident photon and gets excited, to higher energy state. Atom + Photon = Atom*  

5. Spontaneous Emission Atom in the excited state makes transition from high energy state to lower energy state through the emission of photon with energy . Atom* = Atom + Photon  

6. Stimulated Emission If the photon of energy is incident on the atom in the higher energy state, the atom absorbs the incident photon and gets excited, from higher energy state to lower energy state with the emission of photon of energy . Atom* + Photon = Atom + 2  

7. Metastable State Pumping Metastable state is basically an intermediate state between ground state and excited state. The lifetime of metastable state is about M etastable state helps to achieve state of population inversion in laser system.   The mechanism or process of raising an atom from ground state to higher energy state is known as pumping .

8. Ruby Laser Schematic of Ruby laser

9. Construction of Ruby Laser It mainly consist of 3 components Active Material : It is a solid state laser, in which a rod of a synthetic ruby crystal is used as an active medium. A ruby crystal is obtained by doping a small amount of chromium oxide (0.05%)( C ) in aluminum oxide . This chromium ion gives the crystal pink or red color depending upon doping concentration. The length of the ruby rod is usually 2cm to 30cm and the diameter is 0.5cm to 2cm. Pumping Source : The ruby rod is placed inside a helically shaped xenon flash lamp to excite the ion. Thus in ruby laser population inversion is achieved by using optical pumping. Resonator Cavity : the end of the ruby rod are polished such that they becomes flat and parallel to each other. Now one of the end is coated with silver completely w hile the other is partially silvered. Thus, the two silver coated end of the rod acts as an optical resonator system.  

10. Working of Ruby Laser

11. Ruby laser is three energy level laser system. After absorbing light photon of wavelength from xenon lamp, some of the chromium ions at the ground state gets excited to higher energy state . At this state they are unstable and by losing a part of energy to crystal lattice, they fall to metastable state and population inversion is occur between and Now some of the ion will decay spontaneously to ground state by emitting photon of wavelength The photons that are moving parallel to axis of the rod will reflect back and forth by the silvered end of the rod and stimulates other excited ions to radiate another photon with the same phase. Thus due to successive reflections of these photons at the end of the rod, the number of photons multiplies. After few microseconds, a monochromatic , intense and collimated beam of red light of wavelength emerges through the partially silvered end of the rod.  

12. He-Ne Laser Schematic of He-Ne laser

13. Construction of He-Ne Laser It mainly consist of 3 components Active Material : It is a gas laser, which consist of a narrow quartz tube filled with a mixture of helium and neon gases in the ratio of 10:1 respectively. Ne atom acts as a active centers and responsible for the laser action, while He atoms are used to help in the excitation process. Pumping Source : The pumping is done through electrical discharge by using electrode that are connected to high frequency alternating current source. Resonator Cavity : To construct the optical resonator cavity, two parallel mirrors are placed at the end of the quartz tube one of them is partly transparent while other is fully reflecting

14. Working : I t is a four energy level laser system. The electron produced from electric charge collide with the helium and neon atom and excite them to higher energy level to these two states are metastable state so atom may stay there for longer time. They are very close to each other, thus some of the He atoms at state may transfer the energy to the ground state atom through collision and excite them to higher energy level. The kinetic energy of atom provide the additional energy of 0.05eV. Thus He atoms helps to achieve population inversion in Ne atoms. Now some of the neon atom decay spontaneously to lower energy state by emitting a photon of wavelength 632.8nm. The photons that are moving parallel to axis of tube will reflect back and forth by the end mirrors of the rod and stimulate other excited Ne atom to radiate another Photon of the same phase. Thus due to success your reflection of these Photons at the end of the tube, the number of photons multiplies. after a few micro seconds, a monochromatic, intense collimated beam of red light of wavelength of 632.8nm emerges through the partially silvered mirror. The atoms in are unstable and decay spontaneously to lower state and finally they come to ground state by losing their remaining energy through collision with the wall of tube. He- Ne laser operates continuously .  

15. Application of Laser In medicine : To break kidney stone To weld broken tissue (e.g. detached retina) To destroy cancerous and precancerous cells To remove mole, tattoo Used to measure blood cell diameter Can also used for dental treatment In industry : Lasers are used cutting, drilling, welding, cladding, soldering etc .

16. In communication : As laser has large bandwidth, more amount of data can be sent. More channels can be simultaneously transmitted. In Military : Laser can serve as a war weapon. High energy lasers are being employed to destroy enemy air crafts and missiles. Laser beam can be bounced off a target such as enemy air plane or ship, to determine its distance and speed.

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