THE RUBY LASER-A PULSED LASER
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It is the first working laser developed by maiman in 1960. it is a solid stat laser and makes use of the three level scheme of population inversion . It consists of three essential parts:
1. The working material:the working material is a ruby crystal which belongs to a family of gems. actually it is aluminium oxide (Al₂O₃) doped with 0.05% chromium oxide (Cr₂O₃).Thus some of the aluminium atom in the crystal lattice are replaced by
Cr++ion which give ruby a pink colour.
The resonant cavity:It is a specially prepared ruby cylinder in which light intensity can be build up by multiple reflection. For this purpose a ruby laser 20 to 30 cm. and 0.5 to 2 cm in diameter is grown. the crystal is cut polished, so that the ends are flat and parallel, with the end planes perpendicular to the axis of rod.
2.The optical pumping system:The optical pumping is done by an external source. in general ,a helical xenon flash tube acts as a pump
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| fig.1(a) |
All these part of ruby laser are shown schematically in fig.1(a)
Operation: The active material in ruby laser is Cr++ ion. the energy level diagram for for these ion
the optical pumping results when a flash of light from xe flash tube falls upon the ruby rod as a result , the green yellow radiation of lamda =5500 Å are absorbed by the chromium ions which are excited from state E₁to energy state E₃.
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