applied physics nd-yag laser in laser technology

this the principle and working of ND-yag laser

1. Nd- yag laser s.Govardhan 23r01a66h7 Csm -c Sub: Applied Physics

2. Introduction Nd:YAG laser was the first type of laser used in urological practice. It uses a crystal of neodymium that produces a light invisible at a continuous wavelength of 1064 nm. Its reduced absorption by water and tissue determines an increased penetrability into the tissues, of 5–10 mm. 

3. Construction of nd-yag laser

4. Working It is a solid state laser It is a four level laser system Nd-Neodymium ions (Active centres ) YAG-Yttrium Aluminum Garnet Yttrium Aluminum Garnet (YAG) is used as host material and Neodymium is used as host material and Neodymium is used as dopant in place of yttrium the combination of both( Nd:YAG ) is used as LASER medium ,gain medium or active medium . In this LASER ( Xenon and Krypton ) Flash tube & LASER diodes are used as a pump source or energy source

5. Active medium: YAG rod , which is doped by Nd due to doping yttrium ions are replaced by Nd+3 ions Active centres: Nd ions are the active centres in this laser The rod is about 10cm long and 6 to 9 cm diameter Pumping Method : In this laser optical pumping method is involved Energy source: Krypton or Xenon flash tube is used as pumping source

6. working: Here, E 1  is the lowest energy state while E 4  is the highest energy level. However, initially, electrons in E 1  is very much higher as compared to E 4 . So, when external energy is provided in the active medium of the laser. Then the electrons present in the energy state E 1  gains energy and moves to energy state E 4 . However, as E 4  is an unstable state and it exhibits short lifespan .

7. Therefore, electrons that were excited to this state by the application external pumping will not stay at this state for much longer duration and comes to lower energy state E 3  very fastly but without radiating any photon.

8. The energy state E 3  is the metastable state and exhibits longer lifespan. So, the electrons in this particular state will last for a longer duration. Due to this more number of electrons will be present at the metastable state E 3 . Thereby attaining population inversion. But once the lifetime of the electrons at the metastable state gets exhausted then these electrons by releasing photons come to lower energy state E2 E 2  also exhibit shorter lifespan like E 4 . Thus, electrons present in E 2  state will come to E 1  without radiating energy in the form of a photon

9. So, in this way electrons by gaining single photon of energy releases the energy of 2 photons. Also, as the system is equipped with optical resonators so, more number of photons will get generated as the pumped In this way, several electrons on stimulation produce photons thereby generating a coherent laser beam of 1.064 µ m.energy will get reflected inside the active medium .

10. A pplications of LASER: These are used in military applications to find the desired target. This type of laser also finds its application in medical field for the surgical purpose. These are also used in welding and cutting of steel and in communication system also.