1. Principle Characteristics Nd (Neodymium) – YAG (Yttrium Aluminium Garnet) LASER Principle Characteristics Doped Insulator laser refers to yttrium aluminium garnet doped with neodymium. The Nd ion has many energy levels and due to optical pumping these ions are raised to excited levels. During the transition from the metastable state to E1, the laser beam of wavelength 1.064μm is emitted Type:Doped Insulator Laser Active Medium:Yttrium Aluminium Garnet Active Centre:Neodymium Pumping Method :Optical Pumping Pumping Source :Xenon Flash Pump Optical Resonator :Ends of rods silver coated Two mirrors partially and totally reflecting Power Output:20 kWatts Nature of Output :Pulsed Wavelength Emitted :1.064 μm

2. Nd (Neodymium) – YAG (Yttrium Aluminium Garnet) LASER Power Supply Capacitor Resistor Laser Rod Flash Tube M1– 100% reflector mirror M2 – partial reflector mirror

3. E1, E2, E3 – Energy levels of Nd E4 – Meta Stable State E0 – ground State Energy Level Applications Transmission of signals over large distances Long haul communication system Endoscopic applications Remaote sensing Energy Level Diagram of Nd– YAG LASER Non radiative decay Laser 1.064μm Non radiative decay E3 E2 E0 E1 E4 Nd

4. Principle Carbon Di Oxide LASER Principle The transition between the rotational and vibrational energy levels lends to the construction of a molecular gas laser. Nitrogen atoms are raised to the excited state which in turn deliver energy to the CO2 atoms whose energy levels are close to it. Transition takes place between the energy levels of CO2 atoms and the laser beam is emitted. Type:Molecular gas laser Active Medium:Mixture of CO2, N2, He or H2O vapour Active Centre:CO2 Pumping Method:Electric Discharge Method Optical Resonator:Gold mirror or Si mirror coated with Al Power Output:10 kW Nature of Output:Continuous or pulsed Wavelength Emitted:9.6 μm or 10.6 μm

5. Symmetric100C - stationary O - vibrates simultaneously along molecular axis Bending010, 020 C & O vibrate perpendicular to molecular axis Asymmetric Stretching 001, 002 C & O atoms vibrate in opposite directions along molecular axis

7. Applications Bloodless surgery Open air communication Military field

9. Principle The electron in the conduction band combines with a hole in the valence band and the recombination produces radiant energy. This photon induces another electron in the CB to combine with a hole in the VB and thereby stimulate the emission of another photon. Type:Homojunction Semiconductor laser Active Medium:P – N junction Active Centre:Recombination of electrons and holes Pumping Method :Direct Pumping Optical Resonator :Polished junction of diode Power Output:1 mW Nature of Output :Continuous or pulsed Wavelength Emitted :8400 – 8600 Angstrom Units HOMOJUNCTION SEMICONDUCTOR LASER (Ga-As Laser)

12. Applications Compact & used in fibre optic communications CD writer Relieves pain Laser printers

14. Principle Two beams (object beam and reference beam) are superimposed on a holographic plate to form an image called a hologram.

15. Principle A beam of light (reading beam) having the same wavelength as that of the reference beam used for constructing the hologram, is made to fall over the hologram, which in turn gives rise to a 3- D image in the field of view.