Transcript Document

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 E1, 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
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
Nd (Neodymium) – YAG (Yttrium Aluminium
Garnet) LASER
M1– 100%
reflector mirror
M2 – partial
reflector mirror
Laser Rod
Flash Tube
Capacitor
Resistor
Power Supply
Energy Level Diagram of Nd– YAG LASER
E3
Non radiative decay
E2
E4
Laser
1.064μm
E1
Non radiative decay
Nd
E1, E2, E3 – Energy levels of Nd
E4 – Meta Stable State
E0 – ground State Energy Level
E0
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 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
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 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
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 3D image in the
field of view.