The Single-Mode Homogeneously Broadened Laser I: Preliminaries

H. J. Carmichael

L. Mandeļ

Lloyd W. Hillman, Robert W. Boyd, Jerzy S. Krasiński +1 more

Experimental observation has shown that it is no simple matter to make a homogeneously broadened laser operate in a single longitudinal mode. However, elementary theoretical treatments of homogeneously broadening predict that such lasers can operate in only a single mode, because all of the atoms constituting the gain medium experience identical degrees of saturation.

Tang Hui-rong

The expressions and distribution curves of the optimal transmissivity for four-level inhomogeneously broadened single-mode laser are given, and then compares them with those of homogeneously broadened single-mode laser.The characteristics of the inhomogeneously broadened single-mode laser are described.

Wes Hillman, Jiayong Yuan, Karl W. Koch +2 more

I. S. Pashkevich, Iliya V. Doronin, E. S. Andrianov +1 more

The emission linewidth in active medium emerges due to homogeneous and inhomogeneous broadening. We demonstrate that in lasers with inhomogeneous broadening there is a critical pump rate, above which the special mode forms. This mode consists of locked-in oscillations of cavity mode and of the active atoms with different transition frequencies. Below the critical value of the pump rate, the radiation spectrum of the laser has a Gaussian profile, provided that inhomogeneous broadening is dominant. Above the critical value of pump rate, the special mode mostly determines the laser radiation spectrum. As a result, the spectrum attains Lorentz shape characteristic for homogeneous broadening. The formation of the special mode precedes lasing and that the critical pump rate plays the role of lasing prethreshold. We suggest a system where such a transition could be experimentally observed separately from lasing. We obtain expressions for the threshold and generation frequency of a single-mode laser where both homogeneous and inhomogeneous broadening are present.