Mutual coherence of light emitted from the two mirrors of a subthreshold semiconductor laser

Abstract

Experimentally is shown that the left and right output beam of a semiconductor laser are not perfectly correlated, particularly so below threshold. The difference can be attributed to the incoherent contribution of spontaneous emission during a single passage of the laser field through the active medium. The measurements thus provide information on the short-time evolution of the intracavity field. The results are compared with the long-time evolution, as characterized by the linewidth.