21-02-2011, 04:01 PM
presented by:
Bibi Mohanan
CARBON DIOXIDE.ppt (Size: 243 KB / Downloads: 188)
CARBON DIOXIDE LASER
A test target is vaporized and bursts into flame upon irradiation by a high power continuous wave carbon dioxide laser emitting tens of kilowatts of infrared light
Introduction
Operates in middlle infrared region(10.6 μm &9.4 μm )
Operates on rotational –vibrational transitions
Both cw & pulsed laser output
Cw power greater than 100kw
Pulsed energies of 10 kJ
Physical arrangement :a gas filled tube between a pair of mirrors excited by a DC or RF electrical discharge.
Additional gases are added to the gas mixture (besides CO2) to improve efficiency and extend lifetime. The typical gas fill is: 9.5% CO2, 13.5% N2, and 77% He
Excitation Mechanism
Rotational- vibrational transitions
Laser Types
Longitudinally Excited Lasers
Waveguide Lasers
Transversely Excited Lasers
Gas Dynamic Lasers
Longitudinally Excited Lasers
Schematic setup of a sealed-tube carbon dioxide laser.
The gas tube has Brewster windows and is water-cooled
Longitudinally Excited Lasers
Long ,narrow,cylindrically shaped glass enclosures with electrodes at opposite ends from which the discharge excitation current is introduced
Either pulsed or cw
Lengths up to several meters
Two versions
Water coolant jacket is provided
Waveguide Laser
Two transverse RF electrodes separated by insulating sections that form the bore region
RF power supply is connected to the electrodes
Lateral dimensions of the bore –few millimeters
Small bore hence, high pressure operation and rapid heat removal
Hence, high gain and high power output
Cw powers up to 100 W
Commercial air cooled waveguide laser
RF excitation : 80-100 MHz
Four mirrors (two as end mirrors and two for reversing the direction of the beam)
Pressure : 80 Torr
Nitrogen:CO2:Helium =3:1:1
Length :30 cm
Cw power:35 W
Wavelength:10.55μm -10.63 μm
Transversely Excited Lasers
Operates at high gas pressure (1 atm or more)
High voltages are required to ionize the gas
Two electrodes are placed parallel to each other separated by few centimeters
High voltages applied across the electrodes
Pre-ionization is used