Q36
The population inversion in a two-level laser material cannot be achieved by optical pumping because
A.
the rate of upward transitions is equal to the rate of downward transitions
AnswerB.
the upward transitions are forbidden but downward transitions are allowed
C.
the upward transitions are allowed but downward transitions are forbidden
D.
the spontaneous decay rate of the higher level is very low
Answer: Option A
Solution
Answer: Option A
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