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.
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, E1 is the lowest energy state while E4 is the highest energy level.
However, initially, electrons in E1 is very much higher as compared to E4.
• So, when external energy is provided in the active medium of the laser. Then
the electrons present in the energy state E1 gains energy and moves to
energy state E4. However, as E4 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 E3 very fastly but without radiating
any photon.
8. • The energy state E3 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 E3. 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
• E2 also exhibit shorter lifespan like E4. Thus, electrons present in
E2 state will come to E1 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 µm.energy will get
reflected inside the active medium.
10. Applications 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.
