B. F. Kuntsevich

Nonlinear amplitude-detuning characteristic of a CO2 laser with modulated losses

Abstract A complex numerical study of the evolution of the nonlinear response of a CO 2 laser with harmonic and biharmonic loss modulations has been performed with allowance for cavity detuning. We have found that the laser response has specific features which are unambiguously defined by the relationship between the frequency of the loss modulation and the fundamental resonance frequency of the laser.

Nonlinear dynamics of a CO2 laser with current modulation and cavity detuning

A detailed numerical study of the dynamic behaviour of a CO2 laser under current modulation and cavity detuning has been performed on the basis of the complete laser model which takes into account vibrational–vibrational and vibrational–rotational energy exchanges in the active medium. We have shown that due to a relatively fast decrease in the laser response with increasing modulation frequency, nonlinear regimes (period doubling and chaos) can be obtained with cavity detuning either from the line centre or near the laser threshold. Comparison is made with a two-level equation model for the active medium.

FREQUENCY SWEEPING IN A CO2 LASER WITH MODULATED LOSSES

We study the influence of accompanying frequency sweeping on the response of a loss-modulated CO2 laser when cavity detuning is accounted for. The accompanying phase modulation usually manifests itself in an asymmetry of the amplitude-detuning characteristics, i.e., the laser intensity and dynamical regimes depend on the sign of the detuning.

DYNAMIC STABILIZATION OF UNSTABLE PERIODIC ORBITS IN A CO2 LASER BY SLOW MODULATION OF CAVITY DETUNING

We demonstrate numerically and experimentally that a slow modulation of cavity detuning in a loss-modulated CO2 laser can stabilize unstable periodic orbits even when the system remains in a particular dynamical regime for adiabatic changes of the detuning. When the parameter changes faster than the transient response of deformation of the original periodic attractor, the system can evolve toward an unstable periodic orbit.

Influence of variation of the refractive index of a substance under study on CO2-laser output parameters

However, in all of the earlier works it has been believed that the presence of an investigated substance in a laser cavity may cause only a change in laser losses (lifetime of the photons in the cavity). In reality, the change in the losses is accompanied in the majority of cases by a change of the refractive index of the investigated substance. This must lead to a shift of the lasing frequency and, consequently, a change in the gain [6], when determining the intensity (energy density). Therefore, when a change in the intensity (energy density) of laser radiation is evaluated from experimental data, it is necessary to account additionally for the accompanying change of the refractive index of the investigated substance and all of the entailed consequences.

Amplitude modulation of the radiation of a CO2-laser by optically controlled absorption in semiconductors

A number of methods exist for controlling the time parameters of the emission of CO= lasers, based particularly on the change in the optical properties of semiconductors of their compounds when acted upon by an electric field or optical radiation at the semiconductors natural absorption frequency. For example, in [I, 2] modulation of IR radiation was achieved as a result of absorption by charge carriers injected into the n-region of a diode when a dc voltage was applied. In [3, 4] modulators were used based on semiconductor diodes controlled by a change in the width of the F--n junction depletion layer when reverse bias was applied. It is extremely difficult to use such modulators in practice because of their small size. In [5-7] the change in the refl~ction from the semiconductor surface due to the action of radiation of a ruby or a neodymium laser was used to control the time parameters of the emission of CO2 lasers. The power of the controlling radiation required in this case, however, is fairly high.

Dynamical features of a pump-switched waveguide CO2 laser with modulated losses

Abstract The dynamics of a pump-switched waveguide CO 2 laser with sinusoidal loss modulation is investigated experimentally and numerically. The possibilities of shaping the laser pulses by a proper choice of cavity detuning, modulation depth and frequency are studied. An observed asymmetry in the laser response with respect to the sign of cavity detuning is explained by the accompanying change in the refractive index of the modulator. The results of numerical simulations are in a good agreement with experimental results.

Dynamics of a waveguide pulsed-periodic CO2 laser with loss modulation

The nonlinear dynamics of a waveguide CO2 laser with combined periodic loss and pumping modulation is investigated theoretically and experimentally. The possibilities of controlling time and energy parameters of the output radiation using the corresponding selection of the detuning of the cavitys longitudinal mode from the center of the amplification line, the amplitude, and the frequency of loss modulation are demonstrated. The observed asymmetric dependence of the lasing-radiation density on the detuning of the cavity frequency is explained by the attendant modulation of the refractive index of the loss modulator.

Study of vibrational relaxation in the active medium of a CO2-laser by the phase-absorption method

The authors attemps to confirm a modification of the phase-absprotion method applicable to the study of the decay rate of energy stored in the upper level in the active medium of a CO/sub 2/-laser. The essence of the method is described. Relationships are determined which allow one to obtain the unknown parameters of the experimentally measured phase shift. The work exeprimentally shows the possibility of studying vibratioanl relaxation in the active medium of a CO/sub 2/-laser by the phase-absorption method using both ordinary and isotope-substitued molecules.