The threshold pump rate Pth, of a laser is determined by three factors coupling efficiency Beta of spontaneous emission into a lasing mode, a population inversion parameter nsp for a given pump rate, and photon decay rate gamma or a photon lifetime Tplgamma, i.e., Pth,gamma sub spIBeta. The population inversion parameter nsp is given by n, subspEcvEcv-Ecv where Ecv and Evc are stimulated emission and absorption rates for one photon in a lasing mode, respectively. The value of Beta is on the order of 10-4 to 10-5 for a conventional semiconductor laser. To decrease the threshold pump rate Pth, we can increase Beta close to one by using a single-mode cavity.
This article is from 'Organization of the Optical Society of America Photonic Science Topical Meeting Series. Volume 7. Quantum Optoelectronics Held in Salt Lake City, Utah on 11-13 March 1991,' AD-A253 823, p92-95.