Construction of CO, LASER
* It is basically a discharge tube having cross sectional area 1.5 mm? And length 260 mm. The discharge tube is filled with active medium (mixture of gases) carbon dioxide, nitrogen and helium in 1 : 4 : 5 proportions respectively. The active centers are CO, molecules lasing on the transitions between the vibrational levels of the electronic ground state.
* The terminals of the discharge tubes are connected to a D.C. Power supply.
* The ends of the discharge tube are fitted with NaCl Brewster windows so that the laser light generated will be polarized.
* Two concave mirrors one fully reflecting and the other partially form an optical resonator.
* The active medium is a gas mixture of COz, N2 and He. The laser transition takes place between the
When current passes through a mixture of gases, the N2 molecules gets excited to metastable sta.
Given by
N2 +ẻ = Nite
N2 = Nitrogen molecule in ground state
e* = Electron with kinetic energy
N2* = Nitrogen molecules in excited state
e = Same electron with lesser energy
* The excited N, molecules cannot spontaneously lose their energy and consequently the number of l molecule at metastable level builds up.
* No molecules undergo inelastic collisions with ground state COz molecules and excite them to {
N2* + CO2 = CO2 + N2
N2 = Nitrogen molecule in ground state
N2* = Nitrogen molecule in excited state
CO2 = Carbon dioxide atoms in ground state
CO2* = Carbon dioxide atoms in excited state
* Some of COz molecules are also excited to upper level Es through collisions with electrons. Repeo molecules are excited to the metastable state Es where population inversion a at t respect to the two lower lasing levels Ez and E4•
* transtion from is to is sives rise to 106 um wavelength laser and the transition From , %
gives rise to 9.6 um wavelength which are both in the far infrared region.
* elum depopulates the lower energy levels in CO, which facilitates population inversion.
* high eaten dovide laser is a high power laser producing polites hunt . H
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