Self-modulation Regime Research Articles

Self-heterodyning in solid-state ring lasers

Self-heterodyning, resulting from the influence of a weak Doppler-shifted signal on the dynamics of a solid-state ring laser operating in a self-modulation regime of the first kind, was discovered and investigated. It was found that self-heterodyning can increase the efficiency of intracavity coherent detection of weak signals.

Influence of periodic loss modulation on the dynamics of self-modulation oscillations in a solid-state ring laser

A theoretical investigation is made of the influence of periodic modulation of intracavity losses on the dynamics of a solid-state ring laser operating in a type I self-modulation regime. Analytic solutions are obtained for describing dynamic locking of the frequency ωm of self-modulation oscillations to the frequency ωp of periodic loss modulation and a quasi-periodic regime characterised by low-frequency modulation of self-modulation oscillations at the difference frequency ωm—ωp. Analytic expressions are obtained for the width of the region in which locking of the frequency of self-modulation oscillations takes place. Numerical simulation of the dynamics of a solid-state ring laser is used to study the transition of this laser to dynamic chaos when the loss modulation depth h is increased. It is shown that the operational regimes of the laser and the conditions for its transition to dynamic chaos are significantly different in the frequency ranges ωm>ωp and ωm<ωp. The boundaries separating regimes with chaotic, periodic, and quasiperiodic dynamics are found in the (ωp, h) plane.

Parametric resonance in a self-contained solid-state ring laser

The interaction between self-modulation and relaxation oscillations in a solid-state ring laser operating in a self-modulation regime of the first kind is investigated theoretically. It is shown that the regions of parametric resonances between the self-modulation and relaxation oscillations have a strong influence on the stability of the former oscillations. The limits of the parametric instability bands and growth increments of the relaxation oscillations are found.

Relaxation oscillations in a self-modulated solid-state ring laser

Noise driven relaxation oscillations of a solid-state ring laser undergoing stable dynamical periodic pulsation are investigated for the first time. Formulas for the relaxation oscillation frequencies in the presence of frequency nonreciprocity are derived. It is shown that, in the case of symmetric backscattering, the self-modulation regime is characterized by damped relaxation oscillations. The conditions are found for which the relaxation oscillation frequencies are nondegenerate over the whole range in which the frequency nonreciprocity can be varied. The dependence of the relaxation oscillation frequencies on parameters of the sinusoidally alternating bidirectional ring laser is substantially different from the corresponding dependence for unidirectional operation.

Use of self-modulation regime in a ring laser in optical nonreciprocity measurements

A new method for determining the optical nonreciprocity is suggested and analyzed. The method is based on the use of a ring laser operating in the self-modulation regime with a variable-sign frequency ''pedestal.'' The example of a ring YAG laser is used to show that this method should make it possible to reduce greatly the experimental error.

Langmuir turbulence as a critical phenomenon. Part 2. Application of the dynamical renormalization group method

In part 1 of this work, we have found a ‘critical curve’ which separates the unstable self-modulation regime from the stable one for a Gibbs ensemble of interacting modes. On this critical curve, the correlation length diverges and scaling invariance occurs; in particular, the Langmuir correlation spectrum is proportional to k-2. Simple laws have been derived for the neighbourhood of the critical curve. However these derivations are based on equilibrium statistical mechanics and the results are obtained with a Hartree approximation which has not been checked. So, in this second part, we elaborate a direct statistical theory of Zakharov's equations completed by excitation sources and dissipations. In spite of infra-red divergences and a large fluctuation level, large-scale properties are derived in the neighbourhood of the critical curve, by the renormalization group method. The laws obtained in part 1 are slightly modified; however, the same spectrum is obtained.

Self-oscillation instability in fast-flow lasers with unstable resonators

An analysis is made of the influence of pumping of the active medium and energy exchange between N2 and CO2 in an unstable resonator zone on the operating conditions of fast-flow carbon dioxide lasers. Explicit expressions are derived for the perturbation growth rate and the dependence of the boundary of the stable region on the parameters of the medium and resonators. Estimates are made of the radiation pulse durations in the self-modulation regime.

Beats in a solid-state ring laser

An investigation is made of the interaction between opposite waves in a solid-state ring laser with a homogeneously broadened gain profile. A solution is obtained for a regime of self-modulation of the intensities and phase differences between the opposite waves in a laser at rest. When the laser is rotated, the self-modulation regime transforms into beats at a sufficiently high angular velocity. Further increase in the angular velocity in the beats regime suppresses one of the opposite waves and reduces the amplitude of the modulation at the beat frequency. Above a certain angular velocity this amplitude vanishes and beats give place to locked opposite waves. The stabilities and ranges of existence of these regimes are investigated.