Unformatted text preview: you have already determined all the parameters for this laser that you did for Paoli’s laser ‘A’ in homeworks #8, #9 and #10. (1) Write the equation for d η /dt that is analogous to the Model A equation for dn/dt . (2) Write the fraction ε of incoming electrons that results in the emission of a spontaneous photon in CW LED operation. (3) Integrate the equation in (2) to find an integral that gives η (t) in terms of i(t) . Assume the diode current i(t) was until t=0 (when η had a known value η 0 ) and then varied arbitrarily ( but always well below i th ) with t after that. (4) When i(t)=i +i 1 cos( ω t) < i th , do the integral in (3) to find the resulting expression for η (t). (5) The exciton lifetime τ 2 can be made to vary in time, for example, by an impressed magnetic field. Find the simple change you can make in your answer to (3) that keeps it exact even when τ 2 is timevarying....
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 Spring '08
 Hellwarth

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