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Unformatted text preview: are emitted from the optical system when the atom is known to be in its upper state. The fraction of photons which cause stimulated emission n se is recorded. Neglecting all sources of experimental error, how does n abs compare to n se ? (b) Give an approximate range for reasonable values of the stimulated emission cross section, σ for laser transitions. (c) If a laser is pumped 35% above threshold, what is the net round trip gain? 3 Einstein Coeﬃcients In the study of blackbody radiation and lineshape, many new quantities were introduced. Look at equations in the notes and in the book involving the following quantities and determine their units: (a) N 1 (b) A 21 (c) B 21 (d) g 1 (e) A 21 N 2 2 (f) ρ ( ν ) (g) I ν (h) σ (i) σ ( ν ) (j) γ 21 (k) dN 2 dt (l) B 21 N 2 (m) B 21 N 2 ρ ( ν )Δ ν (n) R B 21 N 2 ρ ( ν ) dν (o) R g ( ν ) dν (p) σ ( N 2-N 1 ) 3...
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- Fall '08
- Light, researcher, Stimulated emission, 35%, single photons