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RUBY LASER - CONSTRUCTION AND WORKING

 Ruby laser 

 Ruby laser is a solid state laser. Ruby is a transparent crystal of aluminium oxide and its chemical composition is  Al2O3. An amount of aluminium atoms are replaced by chromium atoms with 0.5%. Then the crystal (Al2O3, Cr2O3) will attain a light pink
colour. 

Construction :  

A ruby rod of length 4 cm and diameter 0.5 cm to 1 cm is used . The end faces of the rod are grounded  and polished to be parallel to each other. One face of the rod is silvered and it acts s perfect reflector. The other face is semi silvered. The ruby rod is surrounded by an optical flash helical pipe filled with Xenon gas. The two ends of Xenon pipe are connected to a high tension voltage for pumping the chromium ions to excited state. The whole arrangement is enclosed in an evacuated chamber. 




Working  :  
Ruby laser works  on 4 level pumping principle. 
when the high tension is applied the xenon pipe releases white light. 
The cr+ atoms will reach to two excited levels ‘E3’ and ‘E3’’ from ground level   ‘E1’ by absorbing green and  Blue wavelengths.
Some of the Cr+ ions in E3’  will reach to E2 level  and remaining ions reach to E1 ( ground level) spontaneously after 10 ^ -19 sec.
During this transition the released energy is used for thermal agitation of Al+ ions. 
The pumping  of Cr+ atoms is continued by means of High tension voltage from E1 to E3’ level. 
E2 level is meta stable level and the life time of Cr atoms in E2 level is about 10^-3 to 10^-6 sec.    It is far greater 1000 times of E3’ level.
After some time the condition is achieved such that the number of atoms in E2 is greater than that of E1 ( N2 > N1 ). 
population inversion is  created between the states E2 and E1.
At this condition Cr atoms in E2 level  are stimulated by the  wavelength  6943 A, ( equal to red) , and lasing action is started. Hence a powerful laser of wave length 6943 A  is released in between E2 and E1. 

 pumping process in ruby laser
 Disadvantages  of  Ruby laser: 
1. It requires a very high tension for pumping. 
2.The efficiency is very low. 
3.The Cr atoms use only blue nad green wavelengths and the remaining wavelengths are unused. 
4 It is not continuous.
5.The crystal defects impress the power of laser. 


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