Ring Gas Laser Research Articles

Possibility of reducing nonlinear distortions of a frequency response of a gas ring laser with a periodic alternating frequency bias

We report a theoretical study of the dependence of the beat frequency of counterpropagating waves on the rotation velocity in a gas ring laser with a periodic alternating frequency bias. Rectangular biases of two types are considered: with constant amplitude and with periodic amplitude modulation. We have found dynamic zones for locking-in the counterpropagating wave frequencies and determined deviations of the frequency response from the ideal one that arise when measuring frequency nonreciprocities, close in magnitude to the amplitude of an alternating frequency bias. It is shown that in the case of a rectangular bias with periodic amplitude modulation, nonlinear distortions of the frequency response can be reduced by an order of magnitude.

Frequency characteristics of a gas coupled-cavity ring laser

Based on a theoretical model describing the lasing dynamics in a gas ring laser (GRL) with coupled cavities, we have investigated the frequency characteristics of radiation. The conditions are found under which an increase in the scale factor is the largest. The regime of frequency locking of counterpropagating waves is studied. It is shown that the lock-in region in a GRL with an antiphase optical coupling of the cavities remains the same as without an additional cavity. The conditions are determined under which multistability of the radiation characteristics arises in a coupled-cavity GRL. In the numerical solution of the equations of the considered theoretical model, three branches of the frequency response are found.

Spontaneous phase symmetry breaking in a gas coupled-cavity ring laser

A theoretical model is proposed that describes the lasing dynamics in a gas ring laser (GRL) with coupled cavities. The conditions are found under which spontaneous phase symmetry of counterpropagating waves is broken in the GRL with an antiphase optical coupling of the cavities. It is shown that in the case of spontaneous phase symmetry breaking, two branches appear on the GRL frequency characteristic. In some region of frequency nonreciprocity of a ring cavity, both branches can exist under the same conditions. In this case, radiation bistability appears in the GRL, and hysteresis phenomena can be observed.

Frequency response of a gas ring laser with a variable-sign frequency bias in the case of frequency nonreciprocity comparable with the bias amplitude

The dependence of the beat frequency of counterpropagating waves on the rotation rate is studied theoretically and experimentally in a gas ring laser (GRL) with a Zeeman effect-based, variable-sign frequency bias. Use is made of magneto-optical biases of two types, namely, a rectangular (meander) bias and a combined bias consisting of fast and slow meanders. At high rotation rates, when the frequency nonreciprocity determined by the rotation rate is close in magnitude to the amplitude of the variable-sign frequency bias, the dynamic locking bands take maximum values and there arise the most extensive deviations of the frequency response from the ideal response. Comparison of experimental and theoretical results for the widths of dynamic bands that appear in this region of the measured rotation rates shows good agreement between theory and experiment. The results suggest that the frequency response of a GRL in this region can be described by one differential equation for the phase difference of counterpropagating waves.

Resonances of intensities and oscillation frequencies in ring gas lasers. II

Resonances of intensities and oscillation frequencies in ring gas lasers. II

Resonances of intensities and oscillation frequencies in ring gas lasers. I

Narrow resonances of the intensities and oscillation frequencies of counterpropagating waves in the vicinity of the center of the quantum transition in a pure-isotope ring gas laser have been studied. It is shown that the origin of resonances is related to the presence of sources causing unequal losses and/or frequencies of the counterpropagating waves in the laser cavity. The resonance change of intensities, which is accompanied by the resonance behavior of the medium dispersion for each of the waves, is not related to resonance changes of the saturated gain coefficients of the nonlinear medium. The resonances are caused by the redistribution of energy between the waves. The character of resonance changes of frequencies and intensities depends on the nature of nonreciprocity present in the cavity.

Phase instability in a four-frequency anisotropic-ring cavity gas laser

The nonlinear dynamics of a class A four-frequency ring gas laser with elliptic nonorthogonal states of counterpropagating waves is studied based on a developed and experimentally tested model taking explicitly into account the dependence of the backscattering coefficient of counterpropagating waves on polarisation characteristics. It is shown that the instability of phase characteristics of the generated field cause the switching of the intensities, polarisation states, and phase differences of counterpropagating waves in the self-oscillation regime, the shift of the intensity switching over detuning caused by the phase shift of the wave due to nonzero ellipticity, the spontaneous phase symmetry breaking accompanied by the appearance of deterministic and noise-induced chaos, the multistability of attractors with different topologies, and symmetric and asymmetric chaotic, as well as stochastic oscillations.

Diffraction phenomena in ring gas lasers

The frequency and amplitude diffraction nonreciprocity of counterpropagating waves in a ring gas laser is studied. The self-consistent eigenmode problem is solved within the framework of the model of Gaussian beams for a ring optical resonator containing a nonlinear gaseous medium and a model aperture. The expressions for frequency-dependent losses, frequencies and intensities of counterpropagating waves are obtained and analysed. Experimental data on the influence of diffraction phenomena on the frequencies and intensities of counterpropagating waves reported in the literature are analysed. Nonreciprocal effects related to diffraction are classified by comparing the experimental data with theoretical results. The mechanisms of the asymmetry of the lasing region with respect to the central frequency of the transition and asymmetry of the laser line are explained.

Polarization-phase dynamics in a four-frequency gas ring laser with elliptical polarization of counter-propagating waves

Based on a developed and experimentally tested model, self-oscillatory lasing regimes have been studied for a Class A four-frequency gas ring laser with linear coupling of elliptically polarized counter-propagating waves. In the self-oscillatory regime, switching of the intensities, polarization states, and phase differences of the counter-propagating waves is observed, and also a polarization-phase dynamics effect involving displacement of the intensity switching point (with respect to detuning), due to the phase shift as a result of an ellipticity different from zero.

The ultrahigh resolution and sensitivity by spectral measurement on the basis of the ring laser

The laser gyroscope technique on the basis of the gas ring laser at use in the spectral dispersive and absorptive analysis of substance allows attaining to the ultrahigh frequency resolution (about 10 −16 and less). Experimental check of a method is realized on the basis of air research on dispersive dependence.

Chaos induced by noise in a four-frequency ring gas laser

In a four-frequency class A ring gas laser with linear coupling of elliptically polarized counterpropagating waves, periodic regimes of lasing with oscillations of the intensity of one of the waves close to the threshold were revealed. Stochastization of these oscillations in the presence of a low-level δ-correlated white noise gives rise to the appearance of asymmetric chaos, evolving with a change in the detuning from the line center to symmetric chaos.

Spontaneous phase symmetry breaking in a four-frequency ring gas laser

Lasing regimes of a single-mode four-frequency class-A ring gas laser with elliptical polarization of the emitted waves are studied numerically. Stationary regimes typical of both standing-and traveling-wave lasing are discovered. Self-oscillations exhibiting the properties of asymmetric and symmetric limit cycles are also found. It is shown that transition between cycles with different symmetry may result in the spontaneous phase symmetry breaking and the appearance of chaos arising due to the period doubling bifurcation cascade of the asymmetric limit cycle.

Unidirectional generation regime of a ring gas laser

Based on solving a boundary problem for a ring gas laser with a reversal mirror, conditions necessary for the realization of the unidirectional generation regime are established. Under these conditions, anomalies arise in the frequency dependence of the laser energy. They are manifested through the occurrence of relatively high peaks compared to the conventional Lamb dip. The unidirectional generation regime has been realized for an argon laser at a wavelength of 4880 A.

Letter to the editor of the Optics and Spectroscopy journal “two attitudes on the question of nonlinear diffraction amplitude-frequency nonreciprocity of counterpropagating waves in a ring gas laser”

Letter to the editor of the Optics and Spectroscopy journal “two attitudes on the question of nonlinear diffraction amplitude-frequency nonreciprocity of counterpropagating waves in a ring gas laser”

An answer to the letter “two attitudes on the question of nonlinear diffraction amplitude-frequency nonreciprocity of counterpropagating waves in a ring gas laser”

An answer to the letter “two attitudes on the question of nonlinear diffraction amplitude-frequency nonreciprocity of counterpropagating waves in a ring gas laser”

Mechanism of the appearance of a diffractive nonreciprocity in a ring gas laser

It is shown theoretically that diffraction leads to a difference between the losses and phase velocities of counterpropagating waves in ring gas lasers. This is the cause of the appearance of the amplitude and frequency nonreciprocity of these waves.

The mechanism of the diffractive nonreciprocity of counterpropagating waves in a ring gas laser

The mechanism of the appearance of the diffraction nonreciprocity of counterpropagating waves in a ring gas laser is examined. Formulas were obtained for the difference between their frequencies and intensities, the dependences of which on the detuning agree with those obtained earlier and with experiment. Explicit dependences of the differences between the frequencies and intensities of the counterpropagating waves on the cross sections of the aperture and of the Gaussian beams incident on the latter were found.

Ring gas lasers with magneto-optical control for laser gyroscopy (invited paper)

The main physical principles of the operation of ring gas lasers in the laser-gyroscope regime are examined. The influence of nonreciprocal effects on the operational parameters of ring gas lasers and the methods of controlling, with the aid of the nonreciprocal magneto-optical Zeeman effect, the parameters of these lasers used in gyroscopes are discussed.

Splitting of oscillation frequencies of a ring gas laser caused by the diffraction lens effect: II. Nonlinear theory

An analysis is made of the problem of generating the fundamental mode in a laser cavity containing a weakly nonlinear active medium and an aperture. Frequency-dependent nonlinear loss of counterpropagating waves is calculated. The loss was found to have a jumpwise decrease at the boundary of the lasing region. An explanation is given regarding the mechanism responsible for the asymmetry of loss about the central frequency of the transition. It is shown that counterpropagating waves differ in loss, as well as in the phase velocity, which is one of the reasons of that the counterpropagating waves of a ring laser, without special nonreciprocal devices, have different frequencies and intensities.

Investigation of NbN phonon-cooled HEB mixers at 2.5 THz

The development of superconducting hot electron bolometric (HEB) mixers has been a big step forward in the direction of quantum noise limited mixer performance at THz frequencies. Such mixers are crucial for the upcoming generation of airborne and spaceborne THz heterodyne receivers. In this paper we report on new results on a phonon-cooled NbN HEB mixer using e-beam lithography. The superconducting film is 3 nm thick. The mixer is 0.2 /spl mu/m long and 1.5 /spl mu/m wide and it is integrated in a spiral antenna on a Si substrate. The device is quasi-optically coupled through a Si lens and a dielectric beam combiner to the radiation of an optically pumped FIR ring gas laser cavity. The performance of the mixer at different THz frequencies from 0.69 to 2.55 THz with an emphasis on 2.52 THz is demonstrated. At 2.52 THz minimum DSB noise temperatures of 4200 K have been achieved at an IF of 1.5 GHz and a bandwidth of 40 MHz with the mixer mounted in a cryostat and a 0.8 m long signal path in air.