On the natural fluctuations of the intensity and frequency of a two-mode laser

R. Graham, Wallace Arden Smith

M. M-Tehrani, L. Mandeļ

The light intensities of the two counter-rotating modes of a ring laser have been investigated by photoelectric counting measurements near the laser threshold and for various detunings. The results are found to be in good quantitative agreement with the theory. They confirm that, at the line center, competition effects prevent the light output in one mode from growing and becoming coherent as the pump parameter is increased. Instead the relative intensity fluctuations of this mode become unity, as for thermal light. Negative cross correlations between the intensity fluctuations of the two modes are also measured. The competition effects virtually disappear when the laser is detuned three natural linewidths from line center, and an intermediate situation is found for smaller detuning.

GORDON J. TROUP

E G Lariontsev

We study the field correlation functions and the natural laser spectrum for a slow-inversion laser with the thresholdless intensity fluctuations. In such a laser, the spontaneous-emission-driven relaxation oscillations are responsible for some unique features: The field correlation function oscillates with the frequency of relaxation oscillations ${\ensuremath{\omega}}_{r}$ and the laser line changes its profile. We show that appreciably above threshold the laser spectrum consists of three lines. In addition to the main line at the frequency of the lasing mode ${\ensuremath{\omega}}_{c}$ appear two lines at frequencies ${\ensuremath{\omega}}_{c}+{\ensuremath{\omega}}_{r}$ and ${\ensuremath{\omega}}_{c}\ensuremath{-}{\ensuremath{\omega}}_{r}$. The spontaneous emission noise in such lasers gives rise to nonlinear stochastic effects: Quantum noise affects the oscillation frequency ${\ensuremath{\omega}}_{r}$ and the decay rates of the field correlation function.

Hermann Haken

Bradley M. Jost, Bahaa E. A. Saleh

We investigate the statistical properties of the optical field that arises from two-wave mixing in a single-mode unidirectional photorefractive ring resonator. Two cases are considered: additive noise produced by generation-recombination fluctuations in the photorefractive material's ionized donor concentration and multiplicative noise produced by fluctuations in the cavity detuning and losses. Like the homogeneously broadened two-level laser near threshold, the photorefractive resonator has Gaussian and Rayleigh-like intensity distributions in the additive and multiplicative noise cases, respectively. The equations describing the linewidths associated with the intensity fluctuations for the two cases and those describing the linewidth and frequency shift associated with the amplitude fluctuation in the multiplicative noise case also have the same form as the laser equations. The descriptions of the linewidth and frequency shift associated with the amplitude fluctuation in the additive noise case are, in general, different from those of the laser.>