Abstract

The problem of converting ambient heat into luminescence radiation is analyzed in terms of the thermodynamics of the electromagnetic field. The process is described in terms of the technical efficiency of a light source η, defined as the ratio of the power leaving the source in the form of luminescence radiation to the power supplied to the source in the form of work. For a source at the ambient temperature T, it is shown that the limitation imposed by thermodynamics is, in the steady state, η≤1+T/(TfT), where Tf is the ratio of the net rate at which the field carries energy away from the source to the net rate at which the field carries entropy away from the source as a result of the luminescence emission. Thus, T/(TfT) is the maximum possible contribution of ambient heat to the technical efficiency of a light source.

An explicit expression for Tf in terms of the ambient temperature and the spectral distribution of the luminescence emission is obtained. It is shown that TfT, and that Tf is a monotonic increasing function of the ratio of the integrated intensity of the luminescence emission to the bandwidth of the emission spectrum. For moderate integrated intensities and finite (but narrow) bandwidths, it is shown that Tf is approximately equal to the brightness temperature of the light source, and it is concluded that thermodynamics forbids technical efficiencies greater than about 160% for room-temperature light sources of practical brightness. As an example, Tf is calculated for the (green) emission band of a typical ZnS phosphor.

© 1960 Optical Society of America

Full Article  |  PDF Article
OSA Recommended Articles
Thermodynamic limit to light trapping in thin planar structures

Howard R. Stuart and Dennis G. Hall
J. Opt. Soc. Am. A 14(11) 3001-3008 (1997)

Thermodynamics of radiation-balanced lasing

Carl E. Mungan
J. Opt. Soc. Am. B 20(5) 1075-1082 (2003)

Noise Limitations in Solid State Photodetectors

K. M. van Vliet
Appl. Opt. 6(7) 1145-1169 (1967)

References

You do not have subscription access to this journal. Citation lists with outbound citation links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Cited By

You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription

Equations (48)

You do not have subscription access to this journal. Equations are available to subscribers only. You may subscribe either as an OSA member, or as an authorized user of your institution.

Contact your librarian or system administrator
or
Login to access OSA Member Subscription