Nd (Neodymium) – YAG (Yttrium Aluminium Garnet) LASER Lect_2

     Gas lasers

Gas laser in the tubes is electrically in the similar to common in the fluorescent lights or in the neon signs. When high in the voltage is applied, in the gas in the tube in the ionizes and in the produces a glowing light.
, In the perfectly aligned mirrors gather and in the concentrate a specific in the wavelength of light in the produced by the gas into an intense laser in the beam.
Gas lasers produce in the extremely high- in the quality laser in the beams, many of which are of very high in the power, in the suitable in the for cutting, in the welding, and even some in the military in the applications.
 

CO2  ( Carbon dioxide ) LASER

Principle :

The transition in the between in the rotational and vibrational in the energy levels in the leads to the construction of a molecular in the gas laser. Nitrogen in the in the atoms are raised to the excited in the state which in turn delivers energy to the CO2 atoms whose energy levels are close to it. The transition in the takes place in the between the energy in the levels of CO2 in the atoms and the laser in the beam is emitted.
Characteristics :

Type Ø: Molecular gas laser
Active in the Medium Ø: Mixture of CO2, in the N2, He or H2O vapour
Active Centre Ø: CO2
Pumping Method Ø: Electric Discharge Method
Optical in the Resonator Ø: Gold mirror or Si mirror in the coated with Al
 in the Power Output Ø: 10 kW
Nature of Output Ø:  in the Continuous or pulsed
Wavelength Emitted Ø: 9.6 μm or 10.7 μm

 

Carbon Dioxide Laser


The CO2 laser operates analogously.  N2 is pumped, transferring the energy to CO2.
A carbon in the dioxide in the (CO2) laser can in the produce a continuous laser beam with a power output of several kilowatts while, at the same time, can in the maintain high degree of spectra in the l purity and spatial in the coherence.
In comparison in the with atoms and ions, the energy level in the structure of molecules is more in the in the complicated and in the originates from three sources: in the electronic in the motions, in the vibrational motions and rotational motions.

Modes of vibration in CO2

Symmetric C – stationary
O – vibrates simultaneously along molecular axis
Bending C & O vibrate perpendicular to the molecular axis
Asymmetric Stretching C & O atoms vibrate in opposite directions along the molecular axis

 
ü The energy in the level diagram of vibrational – in the in the rotational energy in the levels with which in the main physical in the processes taking in the place in this laser.
ü As the electric in the discharge is passed in the through the tube, which contains a mixture in the of carbon dioxide, nitrogen and helium in the gases, the electrons in the striking nitrogen in the molecules impart in the sufficient energy to in the raise them to their first excited in the vibrational-rotational in the energy level.

üThis energy in the level in the corresponds to one of the in the vibrational – in the rotational levels in the of CO2 in the molecules, designated as level 4.
ü in the Collision with N2 in the molecules, in the CO2 molecules in the are raised in the to level 4.
üThe lifetime of in the CO2 molecules in the in level 4 is quite in the significant to serve practically as a metastable state.
ü  Hence, in the population inversion of CO2 molecules is established between levels 4 and 3, and between levels 4 and 2.
ü  The transition of CO2 in the molecules in the between levels 4 in the and 8 in the produce lasers of wavelength 10.6 in the microns and that in the between levels 1 and 4 in the produce lasers of wavelength 9.8 in the microns.
ü  The He molecules increase in the population of level 4, and also help in in the emptying the lower laser in the levels.
ü  The molecules that arrive at the levels 3 and 2 decay to the ground in the state through in the radiative and collision-induced transitions in the to the lower in the level 1, which in turn in the decays to the ground in the state.
üThe power in the output of a CO2 laser in the increases in the linearly with length. Low power (upto 50W) continuous wave CO2 in the lasers are available in sealed tube in the configurations.

Application of CO2 Laser

  •  in the Because of the high in the power levels available ( in the combined with a reasonable in the cost for the laser), CO2lasers are in the frequently in the used in industrial in the applications for cutting and welding, while lower in the power level in the lasers are used for engraving.
  • They are also in the very useful in surgical in the procedures because water (which in the makes up in the most biological tissue) absorbs this frequency in the of light in the very well. Some in the examples of medical uses are laser surgery in the  and skin resurfacing (“laser facelifts”, which essentially consist of vaporizing the skin to promote collagen formation). Also, it could be used to treat in the certain skin in the conditions such as hirsuties papillaris genitalis by removing embarrassing or in the annoying in the bumps, podules, etc. Researchers in Israel are experimenting with using CO2 in the  lasers to weld in the human tissue, as an alternative to in the traditional sutures.
  • The common in the plastic poly in the (methyl methacrylate) ( in the PMMA) absorbs in the IR light in the 2.8–25 µm in the wavelength band, so in the CO2lasers have been used in recent in the years for fabricating in the microfluidic device in the from it, with channel in the widths of a few hundred in the micrometers.
  • Because in the atmosphere is in the quite in the transparent to infrared in the light, CO2 in the lasers are also used for military rangefinding in the using LIDAR in the techniques.
  • CO2lasers are used in the Silex in the process to enrich in the  uranium.
  • The Soviet in the Polyuswas in the designed to use a in the megawatt in the carbon-dioxide in the laser as an orbit to orbit weapon to in the destroy SDI in the satellites.

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