#154-5 Q-Switched Ruby Laser Power. A Q-switched ruby laser makes use of a 15-cm
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Question
#154-5 Q-Switched Ruby Laser Power. A Q-switched ruby laser makes use of a 15-cm-long rod of cross-sectional area 1 cm2 placed in a resonator of length 20 cm. The mirrors have reflectances R 0.95 and R 0.7. The Cr3+ density is 1.58 x 1019 atoms/cm3, and the transition cross section ?(vo)-2x 10-20 cm2 . The laser is pumped to an initial population of 1019 atoms/cm3 in the upper state with negligible population in the lower state. The pump band (level 3) is centered at450 nm and the decay from level 3 to level 2 is fast. The lifetime of level 2 is 3 ms. (a) How much pump power is required to maintain the population in level 2 at 1019 cm-3 (b) How much power is spontaneously radiated before the Q-switch is operated? (c) Determine the peak power, energy, and duration of the Q-switched pulse. 2Explanation / Answer
(a)1.Ruby laser works on the principle of a three level system.
2. The pumping power required for such a system is very high because more than half of the ground state atoms have to be pumped into the upper level to achieve population inversion.
(b) All the power is spontaneously radiated as spontaneous emission takes place immediately.
(c) By experiments, all these factors can be found out.
Peak power is approximately 1.063MW
Peak energy is approximately 371 micro joules
Duration is approximately 349 pico seconds
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