Nd Neodymium YAG Yttrium Aluminium Garnet LASER Principle

Nd (Neodymium) – YAG (Yttrium Aluminium Garnet) LASER Principle 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 E 1, the laser beam of wavelength 1. 064μm is emitted Characteristics Type : Doped Insulator Laser Active Medium : Yttrium Aluminium Garnet Active Centre : Neodymium Pumping Method : Optical Pumping Source : Xenon Flash Pump Optical Resonator : Ends of rods silver coated Two mirrors partially and totally reflecting Power Output : 20 k. Watts Nature of Output : Pulsed Wavelength Emitted : 1. 064 μm

Nd (Neodymium) – YAG (Yttrium Aluminium Garnet) LASER M 1– 100% reflector mirror M 2 – partial reflector mirror Laser Rod Flash Tube Capacitor Resistor Power Supply

Energy Level Diagram of Nd– YAG LASER E 3 Non radiative decay E 2 E 4 Laser 1. 064μm E 1 Non radiative decay Nd E 0 E 1, E 2, E 3 – Energy levels of Nd E 4 – Meta Stable State E 0 – ground State Energy Level Applications Transmission of signals over large distances Long haul communication system Endoscopic applications Remaote sensing

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 CO 2 atoms whose energy levels are close to it. Transition takes place between the energy levels of CO 2 atoms and the laser beam is emitted. Type : Molecular gas laser Active Medium : Mixture of CO 2, N 2, He or H 2 O vapour Active Centre : CO 2 Pumping Method : Electric Discharge Method Optical Resonator : Gold mirror or Si mirror coated with Al Power Output : 10 k. W Nature of Output : Continuous or pulsed Wavelength Emitted : 9. 6 μm or 10. 6 μm

Symmetric 100 C - stationary O - vibrates simultaneously along molecular axis Bending 010, C & O vibrate 020 perpendicular to molecular axis Asymmetric 001, C & O atoms Stretching 002 vibrate in opposite directions along molecular axis

Applications • Bloodless surgery • Open air communication • Military field

HOMOJUNCTION SEMICONDUCTOR LASER (Ga-As Laser) Principle • The electron in the conduction band combines with a hole in the valence band 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 m. W Nature of Output : Continuous or pulsed Wavelength Emitted : 8400 – 8600 Angstrom Units

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

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

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.