NNSE618-L17-emission

NNSE618-L17-emission - NNSE 618 Lecture #17 1 Lecture...

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Unformatted text preview: NNSE 618 Lecture #17 1 Lecture contents • Emission and luminescence – Band-to-band – Recombination processes – Exciton – Donor-acceptor NNSE 618 Lecture #17 2 For two non-degenerate levels Emission and absorption • We have seen previously the relationship between absorption and stimulated emission : • Matrix elements for these transitions are exactly the same • Both processes are proportional to the strength of the optical field • Both treat radiation classically • Spontaneous emission requires quantum mechanical treatment of e-m waves (photons) • Einstein coefficients A and B describe spontaneous emission and absorption/stimulated emission: • Total emission rate With photon energy density [Js/cm 3 ] • And total emission rate (sum of spontaneous and stimulated emission: A and B coefficients are related: 21 3 3 2 21 8 B h c n A r 12 21 B B Density of electromagnetic modes [s/cm 3 ] 21 21 21 B A R N A A B A R 1 1 21 21 21 21 21 Energy density of electromagnetic modes [Js/cm 3 ] Photon occupation number [dimensionless] NNSE 618 Lecture #17 3 Imaginary part of refractive index and the emission rate R cv of pure Ge at 300 K (intraband process can change the spectra) Emission and absorption • Low electromagnetic field...
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This note was uploaded on 11/07/2011 for the course NNSE 618 taught by Professor Sergeoktyabrsky during the Spring '11 term at SUNY Albany.

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NNSE618-L17-emission - NNSE 618 Lecture #17 1 Lecture...

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