A hybrid unstable-waveguide resonator and output characteristics of a gap CO2-laser with high-frequency excitation

Experimentally and theoretically, we investigate the energy and spatial parameters of CO₂-laser generation with a gap active-medium geometry, high-frequency excitation, and an unstable-waveguide resonator. A generation power of 54 W is achieved in the continuous regime with the shape of the output radiation beam close to an axisymmetric one without resorting to external correcting optics. S. A. Esenin Ryazan State Pedagogical University, 46 Svoboda Str., Ryazan, 390000, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 6, pp. 784–790, November–December, 1999.     

Structural transformations of polysaccharides exposed to CO2-laser radiation

We have used IR spectroscopy to study conformational transformations of polysaccharide macromolecules (dextran, pullulan, amylose, and microcrystalline cellulose) and changes in their structural ordering when exposed to cw emission of a CO₂ laser. We have established that the structures of conformationally labile polysaccharides are the most sensitive to laser radiation. The effect of laser treatment is greatest for lower molecular weight polymers. We have observed for the first time changes in the conformational states of dextran macromolecules in the direction of an increase in the structural ordering when exposed to emission from a CO₂ laser. This quite different from purely thermal treatment, where disordering of the polysaccharides structure occurs. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 164–169, March–April, 2006.     

Periodic adjustment of the position of a laser beam spot on a semiconductor saturable absorber mirror in a passively mode-locked solid-state laser

A laser diode end-pumped passively mode-locked Nd:YVO₄ solid-state laser with a semiconductor saturable absorber mirror (SESAM), in which the intracavity laser beam spot on the SESAM can be adjusted periodically, is investigated. Inserting a rectangular prism (RP) into the laser cavity is a promising approach towards the goal of periodically moving the position of the focus spot of the intracavity pulse on the SESAM surface to avoid the long-time irradiation of the laser beam on the same position, thereby solving a series of problems caused by damage to the SESAM and greatly prolonging its usage life. The adjustment of the rectangular prism in the laser cavity does not break the stable continuous wave (CW) mode-locked condition. The laser generates a stable picosecond pulse sequence at 1064 nm with an output power of 3.6 W and a pulse width of 14 ps. The instabilities of the output power and the pulse width are 1.77% and 4.5%, respectively.     

Q-switched and mode-locked diode-pumped Nd:YVO4 laser with an intracavity composite semiconductor saturable absorber

We have demonstrated a passively Q-switched and mode-locked Nd:YVO₄ laser with an intracavity composite semiconductor saturable absorber (ICSSA). Stable Q-switched and mode-locked pulses with Q-switched envelope pulse duration of 180 ns and pulse repetition rate of 72 KHz have been obtained. The maximum average output power was 1.45 W at 8 W incident pump power. The repetition rate of the mode-locked pulses inside the Q-switched envelope was 154 MHz. Experimental results revealed that this ICSSA was suitable for Q-switched and mode-locked solid-state lasers.     

Nonlinear dynamics of the dual-wavelength CO2 laser

Theoretical studies have been made of the nonlinear-dynamic modes of operation of a dual-wavelength CO₂ laser with continuous pumping by electric discharge and loss modulation in one of the lasing channels. It is shown that by varying the modulation depth and frequency, it is possible to control, over a fairly wide range, the time and energy parameters of lasing in both channels, going from regular to chaotic modes of operation. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 316–321, May–June, 2000.     

A measuring system for reflection coefficient investigations of materials heated by CO2-laser radiation in a controllable atmosphere

An experimental system is described which is intended for measurements of reflection coefficients at wavelengths of 0.63; 1.15; 3.39, and 10.6 μm and of the thermodynamic temperature of the surface of materials heated in air or in an inert atmosphere at pressures from 1.3·10² to 1.3·10⁵ Pa. An analysis of the errors in reflection coefficient and temperature measurements is made. B. I. Stepanov Institute of the Physics of the National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 608–611, July–August, 1998.     

Optimization of passively Q-switched laser with V:YAG saturable absorber

By considering the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density, the coupled rate equations for a diode-pumped passively Q-switched laser with V³⁺:YAG saturable absorber are given. These coupled rate equations are solved numerically and the key parameters of an optimally coupled passively Q-switched laser with V³⁺:YAG at 1342 nm are determined. These key parameters include the parameters of the gain medium, the saturable absorber and the resonator, which can maximize the pulse energy of singly Q-switched pulse. The optimal calculations for a diode-pumped passively Q-switched a-Nd:GdVO₄ laser with V³⁺:YAG saturable absorber are presented to demonstrate the numerical simulation applicable.     

Amplitude-detuning characteristic of a CO2 laser with biharmonic loss modulation

The nonlinear response of a CO₂ laser to biharmonic loss modulation was theoretically investigated for tuning of the radiation frequency within the limits of the amplification band. It is shown that the value and form of the amplitude-detuning characteristic (and, consequently, the temporal and energy parameters of the laser radiation) can be controlled within sufficiently wide limits by changing the modulation frequency and the phase shift of oscillations. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 43–47, January–February, 1999.     

Control of the Radiation Parameters of a Two-Wave Repetitively Pulsed CO2 Laser

Generation dynamics of a two-wave CO₂ laser with excitation by a continuous electric discharge and with modulation of losses in one of the channels is investigated theoretically and experimentally. It is shown that by changing the frequency and depth of modulation of a variable component of losses and also the relationship between the constant components of losses one can control, over rather wide limits, the shape, duration, and peak power of radiation pulses in the active and passive channels.     

Dynamics of a Loss-Modulated, Two-Wave CO2 Laser Lasing on Lines of Different Vibrational Bands

The nonlinear dynamics of a loss-modulated, two-wave CO₂ laser lasing on vibrational–rotational lines of different vibrational bands has been investigated theoretically and experimentally. It is shown that the time and energy parameters of laser radiation can be controlled within fairly wide limits by changing the depth and frequency of modulation and the ratio between the constant components of the losses.     

Optimization of passively Q-switched and mode-locked laser with Cr:YAG saturable absorber

By considering the Gaussian spatial distributions of the intracavity photon density and the initial population-inversion density, the coupled rate equations for a diode-pumped passively Q-switched and mode-locked (QML) laser with Cr⁴⁺:YAG saturable absorber are given. These coupled rate equations are solved numerically and the key parameters of an optimally coupled passively QML laser are determined for the first time. These key parameters include the parameters of the gain medium, the saturable absorber and the resonator, which can maximize the pulse energy of singly Q-switched envelope. The optimal calculations for a diode-pumped passively QML Nd:GdVO₄ laser with Cr⁴⁺:YAG saturable absorber are presented to demonstrate the numerical simulation applicable.     

Nonlinear amplitude-tuning characteristic of a CO2 laser with pump-current modulation

The nonlinear amplitude-tuning characteristic of a CO₂ laser with discharge-current modulation was investigated by mean of numerical simulation. It is shown that in the general case the magnitude and shape of the laser response depend on the ratio between the frequency of the pump modulation and the fundamental resonance frequency of the laser. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 640–644, September–October, 1999.     

Raman and Infrared Spectra of Matrix Isolated CO2 and CS2

The matrix isolation infrared and Raman spectra of CO₂ and CS₂ in solid krypton at 20°K are reported. The fundamental frequencies are only very slightly red-shifted from the free gas values. Isotopic effects are found in both infrared and Raman spectra, whereas site splittings are evident in the infrared only.     

Amplitude-detuning characteristic of a CO2 laser with simultaneous modulation of two parameters

Analytical expressions have been obtained in a linear approximation for the amplitude-detuning characteristic of a CO₂ laser with simultaneous modulation of two its parameters. It is shown that the value and form of the laser response can be controlled over a wide range by way of changing the modulation frequency, the value of the detuning, and the phase difference of the oscillations of the simultaneously modulated parameters. B. I. Stepanov Institute of Physics of the Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 190–196, March–April, 1997.     

Effect of detuning on the lasing dynamics of a CO2 laser with a saturable absorber in the resonator

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 3, pp. 457–461, September, 1991.     

Design and operation characteristics of a high power transverse flow pulser sustained cw CO2 laser

A transverse flow, transverse discharge cw CO₂ laser in which de discharge is sustained by employing high repetition rate high voltage pulses has been developed. Pulser sustained discharge through electrodes of innovative design provided uniform excitation at electrical input power densities more than 10 W/cc. Laser output power more than 2.5 kW was obtained in a laser gas mixture consisting of 0.5 mbar of CO₂, 16 mbar of N₂ and 38.5 mbar of He. Design details and operational characteristics of this laser are presented.     

Optimization of the CO2:N2:He Ratio in the Active Media of Continuous-Wave Electric-Discharge CO2 Lasers

It is shown that the optimum ratio between the main components CO₂:N₂:He of the active medium of continuous-wave electric-discharge CO₂ lasers depends on the temperature of the active medium. Continuous-wave CO₂ lasers can operate effectively at high temperatures of their active medium (T 1000 K) if in their composition the fraction of N₂ molecules is increased as compared to the fraction of CO₂ molecules (CO₂:N₂ < 1:15) and the fraction of He atoms is decreased (He n< CO₂ + N₂).