Lasers basics mechanism and principles
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This document discusses lasers and their applications. It begins by explaining the history and science behind how lasers work, including stimulated emission. It then describes key laser characteristics and different types of lasers such as ruby, He-Ne, semiconductor, and dye lasers. Applications are explored in various fields including medicine, industry, communication, military, and more. Lasers are used for applications like laser eye surgery, barcodes, welding, 3D scanning, printers, and holography.
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Lasers basics mechanism and principles
- 1. LASERS & ITS APPLICATIONS
- 2. • In 1917, Albert Einstein first theorized about the process which makes lasers possible called "Stimulated Emission."
- 3. LASER is an acronym for light amplification by Stimulated Emission of radiation. When radiation interacts with matter we have three processes to generate laser light. (1) Optical Absorption (2) Spontaneous Emission (3) Stimulated Emission
- 4. Characteristics of Lasers The most important characteristics of lasers are 1. High Directionality → Angular spread 10 micro radians 2. High Monochromacity 3. High Coherence → (a). Spatial coherence (b). Temporal coherence 4. High Intensity: The number of photons coming out from a laser per second per unit area is given by 2 rh P n υπ =
- 5. Incandescent vs. Laser Light • Many wavelengths • Multidirectional • Incoherent • Monochromatic • Directional • Coherent
- 7. Spontaneous Emission • Incoherent • Less intensity • Poly chromatic • Less directionality • More angular spread • No need of external energy Stimulated emission • Coherent • High intensity • Mono chromatic • High directionality • Less angular spread • External energy is required
- 12. • Video of laser with diffraction grating Lasers and Diffraction Gratings_xvid.avi
- 13. absorption Spontaneou s emission Stimulated emission E1 E2 N1 N2 )(υρ Supplied energy Einstein’s Co-efficients • Consider two energy levels E1 and E2. • N1 and N2 be the number of atoms per unit volume present at the levels E1 and E2 respectively.
- 17. For system in a equilibrium 1 )( )( )( )()( )()( 21 12 2 1 21 21 2112 2 1 21 212121 212 212212121 212212121 − = − = − = =− += B B N N B A v BB N N A v BNBN AN v ANBvNBvN ANBvNBvN ρ ρ ρ ρρ ρρ
- 19. Comparing equations (5) & (6) )8........( 8 )7........( 1 3 3 21 21 212121 2 1 21 12 c h B A BgBg g g B B υπ = = =
- 20. 1) kT h exp(R } 1) kT h exp( 1 { 8 ) 8 ( )( ) 8 ( R 8 )( )( 3 3 3 3 3 3 21 21 212 212 −= − →= = = υ υ υπ υπ ρ υπ ρ ρ c h c h v c h eqfrom Bv A R BvN AN R n The equation shows ratio of spontaneous Emission Rate to stimulated emission rate.
- 21. Population inversion To achieve more stimulated emission population of the excited state N2 should be made larger than the lower state N1 and this condition is called population inversion. E1 E2 N1 N2 12 NN >
- 22. Three level Laser system N E E0 E1 E2 Fast decay Laser transition pumping Meta stable level
- 23. Four level laser system N E E0 E1 E2 Fast decay Laser transition pumping E3 Meta stable state
- 24. ELEMENTS OF A LASER
- 25. Types of LASERS • Solid state Lasers(Ruby laser) • Gas Lasers(He-Ne laser) • Liquid lasers( Europium laser) • Semiconducting lasers( Ga As laser) • Dye lasers(Coumarian laser )
- 26. Ruby LASER 1. Maiman in 1960. 2. Solid State Laser. 3. Active Medium: Al2O3doped with 0.05% Cr3+ ions(10cm long & 0.5cm diameter). 4. Resonant Cavity: Fully reflecting surface & partially reflecting surface. 5. Pumping System: Helical Xenon flash lamp. 6. Three level laser system. 7. Wave Length: 694.3nm. 8. Pulsed Laser. 9. Widely used in Echo technique & Pulsed Holography
- 27. Ruby laser
- 29. N E E0 E1 E2 Fast decay Laser transition 69430 A pumping Meta stable level Energy level diagram of Ruby laser Short lived state
- 30. He-Ne LASER 1.Ali Javan in 1961. 2.Gas Laser.. 3.Active Medium: Helium & Neon Mixture 10:1 ratio... Neon at 0.1mm of Hg and He at 1mm of Hg. 4.Resonat Cavity: Fully & partially reflected surfaces… 5.Pumping System: Discharge electrodes… 6.Four level Laser System. 7.Wave Length:632.8nm. 8.Red color Continuous Laser. 9.Widely used in Interferometer Experiments & Holography.
- 31. Discharge electrodes He + Ne (10:1) 0.1mm of Hg Discharge tube Fully reflecting mirror Partially reflecting mirror Laser out put
- 32. Energy level Diagram of He-Ne Laser
- 33. Semiconductor Laser 1.Semiconductor Laser is also called as Diode Laser. 2.The wave length of the emitted light depends upon the Energy band gap of the material. 3.Diode Lasers are always operated in forward bias.. 4.Working Principle: When we apply forward bias to a PN-Diode, charge carrier recombination takes place.. Then in such a process the energy is emitted in the form of light radiation.. 5.Active Medium: Ga Al As diode or Ga AsP diode.. 6.Out put Wave length: GaAlAs:750-900nm,.GaAsP:1100-1600nm.. 7.Pulsed & Continuous Laser 8.Extensively used in fiber optic communication systems because of low cost and small in size.
- 34. • Homo junction semiconductor laser P and n type are from same direct bandgap semiconductors Ex:-p-Ga As ,n-Ga As Draw backs:- 1)Requires high threshold current densities 2)O/p is in pulses 3)Less directional 4)Poor coherence
- 35. • Hetero junction semiconductor laser P and n type are from different direct bandgap semiconductors Ex:-p-Ga As ,n-Al Ga As Draw backs:- 1)Requires less threshold current densities 2)O/p is continuous 3)High directional 4)High coherence
- 36. g g g E hc hc E hE = = = λ λ υ The Energy band gap of a material Where c is the velocity of light & h is Planck's constant.
- 39. LASERS IN DIFFERENT FIELDS • MEDICAL • SCIENTIFIC • INDUSTRIAL &COMMERCIAL • COMMUNICATION • MILITARY • CHEMICAL • OTHERS
- 40. MEDICAL
- 41. • Dermatology • Fractional skin resurfacing • The appearance of facial skin to restore a more youthful appearance • Only five days of healing are necessary
- 42. •stretch marks, sunspots, wrinkles, birthmarks, and hairs ,tattoo removal etc
- 44. • •An endoscope
- 45. LASIK • UV (193 nm) excimer laser is used to reshape the cornea and thus correct a patient’s eyesight • for near-sightedness and/or astigmatism.
- 47. • Laser Welding • Laser Cutting • Laser Trimming • Laser Marking • Barcode readers •INDUSTRIAL &COMMERCIAL APPLICATIONS
- 48. Laser cutting process on a sheet of steel.
- 49. • CO2 lasers are used for industrial cutting of many materials including mild steel, aluminum, stainless steel, titanium, paper, wax, plastics, wood, and fabric • When the material is exposed to laser it produces intense heat, thus the material is heated and melted
- 50. • Cutting and peening of metals and other material, welding, marking, etc. • surveying, • LIDAR / pollution monitoring,
- 52. Communication applications • Optical fibres • Barcode readers • Laser engraving of printing plate • Laser bonding of additive marking materials for decoration and identification, • Laser pointers • Holography
- 54. • 3D laser scanners for accurate 3D measurement. • Laser line levels are used in surveying and construction. Lasers are also used for guidance for aircraft. • . • In laser printers: gas and diode lasers play a key role in manufacturing high resolution printing plates and in image scanning equipment.
- 55. Laser Pointers and Handheld Lasers • Laser pointers are great tools for business presentations, academic lectures, speaking engagements, astronomy, star- pointing, etc. • Green laser pointers are 5 to 20 times brighter than traditional red laser pointers, so visibility is much better on projection screens
- 56. HOLOGRAPHY • Two photographs of a single hologram taken from different viewpoints
- 57. Identigram as a security element in a German identity card
- 58. • Security holograms are very difficult to forge, because they are replicated from a master hologram that requires expensive, specialized and technologically advanced equipment • They are also used in credit and bank cards as well as passports, ID cards, books, DVDs, and sports equipment.
- 59. Quality and applications of laser scanning for civil engineering
- 60. • The laser scanning is capable to provide 3-dimensional information of the surrounding environment for topographic surveys with an accuracy equivalent to traditional land surveys
- 62. COMPUTERS
- 64. A handheld barcode scanner A barcode reader (or barcode scanner) is an electronic device for reading printed barcodes.
- 65. Laser printer
- 66. • A laser printer is a common computer peripheral that rapidly produces high quality text and graphics on plain paper • Respiratory health risks • some printers emit sub-micrometre particles which some suspect may be associated with respiratory diseases
- 70. Common Laser Signs and Labels
- 72. THANK YOU