Basics of LASER and its application.pptx

This presentation talks about various lasers and their application in real world and their hazards

1. BASICS OF LASER by – Aiswarya Dev Goswami 4 r th year,sec-B2 Roll No- 001410801125

2. Full-form of LASER L – Light A - Amplification by S – Stimulated E – Emission of R – Radiation

3. What is LASER ? A laser is a phenomena that transforms light of various frequencies into a monochromatic radiation in the visible, infrared, and ultraviolet regions with all the waves in phase capable of mobilizing immense heat and power when focused at close range. The light emitted from a laser is monochromatic , that is, it is of one wavelength (colour). In contrast, ordinary white light is a combination of many different wavelengths (colours).

4. Invention of LASER: Invented by Charles Townes and Arthur Schawlow in 1958 of Bell Laboratories.

5. Fundamentals of LASER Operation:

6. LASER Action: Light beam is composed of packets of energy known as PHOTONS Ground State – Atoms are normal position Atoms are excited by an energy source and move to a higher energy As it reverts back to its ground state, energy is emitted – Spontaneous Emission Results without external interference and forms waves that are in phase

7. Animation explaining stimulated emission and the laser principle

8. Incandescent Laser Light Many wavelengths Monochromatic Multidirectional Directional Incoherent Coherent

9. HOW COHERENT AND INCOHERENT LIGHT WAVES DIFFERS ?

10. Common Components of all LASERS: Active Medium The active medium may be solid crystals such as ruby or Nd:YAG , liquid dyes, gases like CO2 or Helium/Neon, or semiconductors such as GaAs . Active mediums contain atoms whose electrons may be excited to a metastable energy level by an energy source. 2. Excitation Mechanism Excitation mechanisms pump energy into the active medium by one or more of three basic methods; optical, electrical or chemical.

11. High Reflectance Mirror A mirror which reflects essentially 100% of the laser light. 4. Partially Transmissive Mirror A mirror which reflects less than 100% of the laser light and transmits the remainder. LASER Components:

12. Gas lasers consist of a gas filled tube placed in the laser cavity. A voltage (the external pump source) is applied to the tube to excite the atoms in the gas to a population inversion. The light emitted from this type of laser is normally continuous wave (CW).

13. LASER Output: Continuous Output (CW) Pulsed Output (P)                         Energy (Watts) Time Energy (Joules) watt (W) - Unit of power or radiant flux (1 watt = 1 joule per second). Joule (J) - A unit of energy Energy (Q) The capacity for doing work. Energy content is commonly used to characterize the output from pulsed lasers and is generally expressed in Joules (J). Irradiance (E) - Power per unit area, expressed in watts per square centimeter Time

14. Types of LASER: 1. Based on the mode of operation ( i ) Pulsed Laser systems (ii) High power Q-switched systems (iii) Continuous wave Laser systems 2. Based on the mechanism in which Population Inversion is achieved ( i ) Three level lasers (ii) Four level lasers 3. Based on state of active medium used ( i ) Gas Laser (ii) Solid state Laser (iii) Semiconductor Laser (iv) Tunable dye Laser

15. Pulsed Laser systems:

16. High power Q-switched systems:

17. Continuous wave Laser systems:

18. Three level lasers:

19. Four level lasers:

20. Gas Laser:

21. Solid state Laser:

22. Semiconductor Laser:

23. Tunable dye Laser:

24. Application of LASER: SCIENTIFIC: In science, lasers are used in many ways, including: A wide variety of  interferometric  techniques Raman spectroscopy Laser induced breakdown spectroscopy Atmospheric  remote sensing Investigating  nonlinear optics  phenomena Holographic  techniques employing lasers also contribute to a number of measurement techniques. Laser based  LIght Detection And Ranging (LIDAR)  technology has application in  geology ,  seismology , remote sensing and  atmospheric physics . Lasers have been used aboard spacecraft such as in the  Cassini-Huygens  mission.

25. LASER COOLING: The use of Lasers to achieve extremely low temperatures has advanced to the temperatures of 10e-9 K. These laser cooling can be used for transmitting power without any loss from power station to sub station without the help of power transformers.

26. LASER COMMUNICATION: AT PRESENT The speed of the communication is high, But still the communication with the outer world is still lagging. IN FUTURE Using LASER the communication to other galaxy is possible.

27. COMPUTING SPEED: At present the computing speed ranges from 256 kilobits per second to 1 gigabit per second, which is slow for the present world. The ability to achieve a speed of 25 gigabits per second can be done with the use of laser chips. Lasers are already used to transmit high volumes of computer data over longer distances — for example, between offices, cities and across oceans — using fibre -optic cables. In computer chips, data moves at great speed over the wires inside, then slows when it is sent chip-to-chip inside a computer

28. DEFENCE USAGE: Find Target An infrared camera on the laser continuously scans a 6 to 10-mile radius around the airport for suspicious heat emissions. When it finds a plume, it relays the coordinates to an identification and tracking system, which is also on the unit. Confirm Threat The onboard computer checks the object’s heat signature against a data bank, confirms that it’s a missile (and not a bird or a plane), and activates the laser. Prepare to Fire Reactive gases in the laser’s fuel tanks are funneled through a vacuum tube to heat up atoms and send them cascading through resonator mirrors. This produces a tightly focused, high-energy beam. Destroy Missile The laser-beam cannon emits a burst of intense light aimed at the missile’s most vulnerable spot, usually the explosives compartment. Simultaneously, it sends a signal to airport control tower to give authorities a fix on the origin of the rocket.

29. OTHER USAGES: It is used as the pre-caution system for accidents for an automobile. Laser cutting,  laser welding , laser brazing, laser bending, laser engraving or marking, laser cleaning, weapons etc. When the material is exposed to laser it produces intense heat, thus the material is heated and melted. It has various medical usages like:

30. Cosmetic surgery ( removing tattoos , scars, stretch marks, sunspots, wrinkles, birthmarks, and hairs): see  laser hair removal . Eye surgery  and  refractive surgery . Soft tissue surgery :  CO 2 ,  Er:YAG laser . Laser scalpel  (General surgery, gynecological, urology, laparoscopic). Photobiomodulation  (i.e. laser therapy). No-Touch" removal of tumors, especially of the brain and spinal cord. In  dentistry  for  caries  removal,  endodontic / periodontic   procedures,  tooth whitening , and  oral surgery .

31. LASER Classification system(DEPENDING ON DENGER): >0.5W CLASS 4 Unsafe for eyes Unsafe for skin 0.5W CLASS 3B Unsafe for eyes Generally safe for skin 5mW CLASS 3R Safe with (0.25 s.) aversion response no viewing aids 0.5W CLASS 2M Safe with no viewing aids 1mW CLASS 2 Safe with (0.25 s.) aversion response including viewing aids 0.5W CLASS 1M Safe with no viewing aids 220 μ W to 0.4 μ W CLASS 1 No precautions required Approx. Power Limits for CW Visible Wavelengths Only

32. GENRAL LASER LAB SAFTEY: Never directly view a laser beam. Never point a laser pointer at a person. Never over-ride interlocks Never remove covers from equipment without approval from supervisors – laser, high voltages and other hazards are present. Clothing: Long sleeve clothing should be worn to protect skin. Wear enclosed footwear in labs . Jewelry: watches & rings which could reflect beams should not be worn. Viewing Aids: Never use microscopes, telescopes, magnifying glasses etc to view laser beams

33. THANK YOU