Quantum theory of a two-mode laser (A)

Pierre Meystre, Murray Sargent

S. Swain

We consider the theory of the two-photon laser using the Scully–Lamb theory developed for ordinary single-photon lasers, concentrating on the calculation of the linewidths and the cross-correlation coefficient. In a previous publication we have shown that the quantum-mechanical noise in the modes of a two-mode laser may be highly correlated. Here we show that the same situation appertains to the two-photon laser, that is the two modes are strongly positively cross-correlated when the laser is operating well above threshold. The two-photon laser has the advantage of tunability over the two-mode or quantum-beat laser. The point of using modes whose noise properties are strongly correlated is that in an appropriate two-photon experiment the noises may effectively ‘cancel out’ leaving a very low noise signal. We present a brief development of the two-photon laser theory and show the connection between our work and that of other approaches.

Nadeem A. Ansari, Muhammad Suhail Zubairy

The theory of a two-level quantum-beat laser is presented within the framework of the quantum theory of multiwave mixing. The diffusion coefficients for the relative and the mean of phase angles of the two modes are derived. It is shown that under suitable conditions the diffusion coefficient for the mean angle of the field modes vanishes.

Pierre Meystre, Murray Sargent

Pierre Meystre, Murray Sargent

Surendra Singh, Muhammad Suhail Zubairy

The quantum-statistical properties of the optical field of a two-mode laser with two coupled transitions have been studied by means of a generalization of the Scully and Lamb theory. The photon number distribution and the mode intensity distribution are obtained in the steady state for a system of homogeneously broadened atoms in resonance with the laser field. It is shown that the mode-coupling constant $\ensuremath{\xi}$ is unity and that near threshold the results of earlier treatments are recovered. Furthermore, it is shown that certain limit measures for the relative intensity fluctuations predicted by the semiclassical Fokker-Planck treatments based on the third-order theory are valid even in the limit of arbitrarily high gain levels.