HW5 - are emitted from the optical system when the atom is...

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ECE 455: Optical Electronics Homework 5 Due: October 11, 2011 1 Threshold Gain Find the threshold associated with the following cavities. R refers to the intensity reflectivity of the mirrors. Hash marks or shading indicate the gain medium. (a) (b) (c) It should read: ”Absorber with α = 0.1/cm” (d) Note that the laser beam goes clockwise in this cavity. The two plates labelled R = 50% are beamsplitters. This means that any beam striking the beam splitter will always be 50% transmitted and 50% reflected. 1
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2 Stimulated Processes (a) A researcher finds a way to hold a two-level atom suspended in a vacuum at rest with respect to the laboratory. The atom is placed at the focus of an optical system capable of emitting single photons. The researcher performs two experiments: In Experiment A, single photons are emitted from the optical system when the atom is known to be in its ground state. The fraction of photons which are absorbed, n abs , is recorded. In Experiment B, single photons
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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, for laser transitions. (c) If a laser is pumped 35% above threshold, what is the net round trip gain? 3 Einstein Coecients 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) ( ) (g) I (h) (i) ( ) (j) 21 (k) dN 2 dt (l) B 21 N 2 (m) B 21 N 2 ( ) (n) R B 21 N 2 ( ) d (o) R g ( ) d (p) ( N 2-N 1 ) 3...
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This note was uploaded on 02/28/2012 for the course ECE 455 taught by Professor Eden,j during the Fall '08 term at University of Illinois, Urbana Champaign.

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HW5 - are emitted from the optical system when the atom is...

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