Theory of intensity and phase fluctuations of a homogeneously broadened laser

H. J. Carmichael

Rajarshi Roy, Surendra Singh

Many quantum optical systems exhibit first-order phase transition analogy.1 Fluctuations of the optical field in such systems are due to spontaneous emission noise. The nature of these fluctuations for various systems has been discussed using various approaches. Fully quantum mechanical and Langevin equation treatments have been given for the dye laser2,3 and the laser with a saturable absorber (LSA) with homogeneously broadened media.2,4 For inhomogeneously broadened media, such treatments are either valid for low intensities or do not fully take into account the effect of quantum noise.5 In this contribution we present a fully quantum mechanical treatment for the LSA with an inhomogeneously broadened absorber using the Foch state representation of the density matrix.2,6

K. V. Vladimirskii, A. A. Norvaishas

Surendra Singh, L. Mandeļ

The equations previously derived for the intensity fluctuations of a two-mode ring laser are applied to a homogeneously broadened laser. It is shown that the mean light intensity of the more lossy mode passes through a maximum and then tends to zero as the excitation is increased. The probability distribution of the intensity of each mode may exhibit two peaks, and spontaneous switching between the intensities associated with the peaks may occur. This is manifest in relative intensity fluctuations of the more lossy mode that can be much greater than unity. Estimates are given for the characteristic switching time.

Yu. I. Zaǐtsev

Paul D. Lett, William R. Christian, Surendra Singh +1 more

A homogeneously broadened two-mode ring laser has two metastable states in which one or the other mode intensity is zero. Quantum fluctuations cause the system to switch spontaneously, and at random times, between these states. The probability distribution of the light intensity of one laser mode has been measured, and found to exhibit two completely resolved peaks at zero and nonzero intensities, as predicted. This confirms the existence of a first-order laser phase transition.