Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Photon absorption

Monique Combescot, Shiue-Yuan Shiau

Published Aug 5, 2026• 0 citations
Publisher

Abstract

Abstract The chapter « Photon absorption » tackles a fundamental question: as excitons with a given center-of-mass wave vector are well separated in energy at the exciton Rydberg scale, while the Fermi golden rule requires a final-state continuum to be valid, photons cannot be absorbed in a semiconductor along this rule. An extrinsic exciton broadening must exist for photons to be absorbed. This chapter also discusses the possibility to go beyond the Fermi golden rule, as this rule fundamentally is second order in coupling.

DOI
10.1093/oso/9780198926641.003.0013

Related papers

Photocreation of excitons

Monique Combescot, Shiue-Yuan Shiau

Abstract The chapter « Photocreation of excitons » addresses the creation of excitons by photon absorption. It explains why, for photons to be absorbed in a semiconductor, it is necessary to prevent the formation of long-lived exciton-polaritons by changing the exciton center-of-mass wave vector through collisions with crystal defects or lattice thermal vibrations. The exciton lifetime associated with this broadening dresses the coupled photon with a finite lifetime that ends by producing a photon number decrease, which fundamentally corresponds to photon absorption. The exciton broadening is handled via an energy imaginary part, that is, a nonhermitian photon-exciton Hamiltonian with ket and bra eigenstates. The time evolution of the photon number leads to an optimum absorption that results from the competition between the photon coupling to exciton and the decrease of the coupled exciton number due to wave vector relaxation.

•Aug 5, 2026•0 citations

Dressed atom vs. exciton polariton: From Rabi oscillations to the Fermi golden rule

François Dubin, Monique Combescot, Bernard Roulet

We rederive the dressed atom and the exciton polariton within the same framework to make clear that their major difference only comes from the number of electrons available for photoexcitations. This allows to analytically show how the decrease of the excited-state lifetime transforms the photon number time evolution from oscillations—at the stimulated Rabi frequency for an atom and the vacuum one for semiconductors—to an exponential decay identical for both. Although the matter ground state is in both cases coupled not to a continuum but to a discrete state , broadened by lifetime, this decay yet follows a Fermi golden rule, however having a different scale for the energy conservation. Our work actually provides a clean justification for using the golden rule for exciton absorption.

arXiv:cond-mat/0406554•Europhysics Letters (EPL)•Feb 22, 2005•8 citations

Fermi’s Golden Rule

Debdeep Jena

Abstract This chapter discusses the following questions: • How are time-dependent quantum processes modeled? • Under what conditions is Fermi’s golden rule valid? • How can we use the golden rule to understand electronic and photonic processes in semiconductors? • How do time-dependent processes determine the usefulness of qubits?

•May 26, 2022•0 citations

Fermi's golden rule does not adequately describe Dicke's superradiance

Anatoly A. Svidzinsky, Jun-Tao Chang, Harry J. Lipkin +1 more

We consider the application of Fermi's golden rule to the problem of N atoms, one of which is excited, in an extended medium with dimensions that are large compared with the wavelength. We find that, in contrast to an often-voiced opinion, the golden rule does not describe the physics of one photon absorbed and subsequently emitted by N atoms. The correct treatment includes many-body effects such as Fano interference. For a finite atomic cloud with size R, in the Markovian limit, the system will decay exponentially at a rate of around N(λ2/R 2) faster than the single-atom decay rate.

Journal of Modern Optics•Nov 10, 2008•10 citations

Photon echoes from the absorption continuum of a semiconductor

Stephan Glutsch, Shimshon Bar-Ad, Mary‐Ann Mycek +2 more

\Ve present solutions for the semiconductor Bloch equations under different excitation conditions.By exciting far above the band gap we provide clear theoretical evidence for a photon echo in the absorption continuum of a semiconductor .

Quantum Electronics and Laser Science Conference•May 22, 1995•0 citations

Problem of centers of mass within the problem of the contour of spectral lines. 1. Existence of long trajectories

Stanislav D. Tvorogov

The issue of the renunciation of the long-wave approximation for the centers of mass of molecules in the derivation of the formula for the absorption coefficient is discussed. In this case, in the formula for the absorption coefficient additional operators related to the field wave vector and to the coordinates of the center of mass appear. Their presence results in the appearance of relationships between the absorption coefficients and shifted frequencies; these relationships are called sum rules. Formulas for them in terms of commutators of additional operators with the Hamiltonian of the light-absorbing molecule have been derived. A “drift” hypothesis is presented, which describes the appearance of “long” trajectories going beyond the elementary volume.

Atmospheric and Oceanic Optics•Jun 1, 2009•5 citations
Abstract The chapter « Photon absorption » tackles a fundamental question: as excitons with a given center-of-mass wave vector are well separated in energy at the exciton Rydberg scale, while the Fermi golden rule requires a final-state continuum to be valid, photons cannot be absorbed in a semiconductor along this rule. An extrinsic exciton broadening must exist for photons to be absorbed. This chapter also discusses the possibility to go beyond the Fermi golden rule, as this rule fundamentally is second order in coupling.
Abstract The chapter « Photocreation of excitons » addresses the creation of excitons by photon absorption. It explains why, for photons to be absorbed in a semiconductor, it is necessary to prevent the formation of long-lived exciton-polaritons by changing the exciton center-of-mass wave vector through collisions with crystal defects or lattice thermal vibrations. The exciton lifetime associated with this broadening dresses the coupled photon with a finite lifetime that ends by producing a photon number decrease, which fundamentally corresponds to photon absorption. The exciton broadening is handled via an energy imaginary part, that is, a nonhermitian photon-exciton Hamiltonian with ket and bra eigenstates. The time evolution of the photon number leads to an optimum absorption that results from the competition between the photon coupling to exciton and the decrease of the coupled exciton number due to wave vector relaxation.
We rederive the dressed atom and the exciton polariton within the same framework to make clear that their major difference only comes from the number of electrons available for photoexcitations. This allows to analytically show how the decrease of the excited-state lifetime transforms the photon number time evolution from oscillations—at the stimulated Rabi frequency for an atom and the vacuum one for semiconductors—to an exponential decay identical for both. Although the matter ground state is in both cases coupled not to a continuum but to a discrete state , broadened by lifetime, this decay yet follows a Fermi golden rule, however having a different scale for the energy conservation. Our work actually provides a clean justification for using the golden rule for exciton absorption.
We consider the application of Fermi's golden rule to the problem of N atoms, one of which is excited, in an extended medium with dimensions that are large compared with the wavelength. We find that, in contrast to an often-voiced opinion, the golden rule does not describe the physics of one photon absorbed and subsequently emitted by N atoms. The correct treatment includes many-body effects such as Fano interference. For a finite atomic cloud with size R, in the Markovian limit, the system will decay exponentially at a rate of around N(λ2/R 2) faster than the single-atom decay rate.
The issue of the renunciation of the long-wave approximation for the centers of mass of molecules in the derivation of the formula for the absorption coefficient is discussed. In this case, in the formula for the absorption coefficient additional operators related to the field wave vector and to the coordinates of the center of mass appear. Their presence results in the appearance of relationships between the absorption coefficients and shifted frequencies; these relationships are called sum rules. Formulas for them in terms of commutators of additional operators with the Hamiltonian of the light-absorbing molecule have been derived. A “drift” hypothesis is presented, which describes the appearance of “long” trajectories going beyond the elementary volume.