Lecture16

Photons emiked at the same frequency as the inieal

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: e confined to a cavity and reach an equilibrium temperature T N2 = populaEon of excited state N1 E2 = populaEon of ground state E1 perfect mirror perfect mirror The probability of occupaEon of each level is given by the Boltzmann distribuEon N1 e! E1 / kT = ! E2 / kT N2 e 18 Photon equilibrium Possible transi9ons Spontaneous emission E2 N2 radiaEon in the cavity AbsorpEon E2 ! E1 f= h In thermal equilibrium: N1 e! E1 /kT = ! E2 /kT = e( E1 !E0 )/kT = e!"/kT N2 e STIMULATED EMISSION (book calls “induced”) E1 N1 Postulated by Einstein in 1916. 3rd unknown process required for establishment of equilibrium. ProperEes of induced or STIMULATED emission: 1.  Photons emiked at the same frequency as the iniEal photon (amplificaEon of light at f) 2.  Photons emiked are completely in phase with emiqng photon: coherent radiaEon 19 AbsorpEon E2 N2 radiaEon in the cavity AbsorpEon Rup ! N1 Rup ! # photons at h...
View Full Document

This document was uploaded on 02/04/2014.

Ask a homework question - tutors are online