Results are presented for a TEM laser system with a peak output power of ≥10 kW in several spectral ranges and with an improved design through the use of a combined gas mixture containing inert gases lasing on electronic transitions in addition to CO 2 molecules.

The operating principle and features of the oscillating process for a three-wave CO2 laser with acousto-optic Q-switching are described. Optimization of the active-medium composition and its excitation conditions as well as the choice of oscillating lines allow oscillation with an output power up to 5 W per line in a stable multiwave mode to be obtained. An efficient Q-switching method for a three-wave CO2 laser is demonstrated and enables the output radiation to be controlled in both a wide spectral range and a wide range of modulation frequencies. A method for separating signals with different wavelengths by spacing signals in time has been experimentally implemented using an external selective modulator to simplify data acquisition and processing.

At present there are a number of reports on the development and creation of range-gate vision systems operating in the near-IR range. As radiation sources such systems usually use laser diodes or matrixes and as receiving elements are gated imaginer tubes or highly sensitive CCD matrixes. The principle of operation of such systems is quite simple. The object of observation is illuminated by short laser pulses in the infrared spectral range. In this case, the object is observed in an optical device equipped with a fast shutter opening in time with the sending of light pulses for a certain short time. In the case when the time delay between the moment of a radiation pulse and the moment of opening of the shutter is equal to the time necessary for light to travel the distance to the object and back, the observer will see only the object and the area of the space directly surrounding it. The depth of this space is determined both by the time of the open state of the shutter, and by the duration of the light pulse. This method is sometimes called the range gating method. The method makes it possible to obtain much more contrast images in comparison with conventional laser-illuminated observation systems, especially for the case of a scattering medium (fog, rain, snow, etc.). When the image is formed, the light backscatter from the previous layer of the atmosphere is eliminated by gating the photodetector system. However such systems have common fundamental drawbacks. First, laser sources of the near-IR range have a relatively low output power (in the best systems, diode matrixes arrays of the kilowatt range are used). Secondly, near-IR radiation is substantially scattered on such small inhomogeneous particles present in the atmosphere as droplets of condensate, dust particles, raindrops and snowflakes. This imposes serious limitations on the maximum visibility length in conditions of limited transparency of the atmosphere due to the exponential nature of the dependence of the absorption and scattering processes on the path length. In the literature, even the factor of maximum visibility improvement is used. This factor does not exceed 5 times. These shortcomings will be deprived of range-gate vision system based on a CO 2 laser, for which the radiation peak power of several megawatts is a successfully solved problem. Recently, there have been reports of the beginning of a wide production of photodetector arrays for the mid-IR range, for which pulse gating can be easily organized. In addition, if we use CO 2 lasers tuned on oscillation lines to create vision systems in the mid-IR range, it is not only easy to avoid difficulties associated with the selective absorption of light by the gas components of the atmosphere and water vapor, but also to create systems protected from artificial interference. Such systems will be able to quickly and easily settle from one spectral range to another when trying to jam. For example, a CO 2 laser tunable in the range of 9.2-10.8 μm can provide efficient operation on several dozen generation lines suitable for use in the absence of interaction with absorbing gas components of the atmosphere. Involving the so-called non-traditional transitions of the CO 2 molecule can increase the number of such lines to several hundred.

For gated viewing systems with triangular and trapezoidal illuminating pulses, we have obtained the range-intensity profiles (RIPs) of the signal as the time delay was varied between the leading edges of the gate pulse and the illuminating pulse. We have established that if the duration of the illuminating pulse Δtlas is less than or equal to the duration of the gate pulse ΔtIC, then the expressions for the characteristic distances are the same as for rectangular pulses and they can be used to determine the distance to objects. When Δtlas > ΔtIC, in the case of triangular illuminating pulses the RIP is bell-shaped. For trapezoidal pulses, the RIP is bell-shaped with or without a plateau section. We propose an empirical method for determining the characteristic distances to the RIP maximum and the boundary points for the plateau section, which we then use to calculate the distance to the object. Using calibration constants, we propose a method for determining the distance to an object and we have experimentally confirmed the feasibility of this method.

It is shown that four rays can be identified which determine the basic characteristic of the visibility zone for observation along an inclined path. Their origin is interpreted physically and analytic expressions for the ray lengths are obtained. Characteristic points on the observed surface are indicated which could be detected as an image on a monitor. The analytically determined distances to the characteristic points are in good agreement with experiment. Maximal use of the laser illuminator energy for viewing along an inclined path requires that the angular divergence of the illumination be consistent with the illuminator pulse duration, the strobe pulse duration, and the strobe delay time.

It is found analytically and experimentally that four characteristic distances intervals can generally be distinguished in the formation of images of objects in active pulse vision systems. A physical interpretation of their origin is given. Four algorithms are proposed for determining the distance to objects using the characteristic distances or for measuring calibration constants. The depth of the visibility zone is found to depend on the sum of the durations of the laser illumination pulse and the strobe pulse of the receiver system.

The ability of a CO 2 laser to oscillate in the range of 16 (14) μm at room temperature was investigated experimentally and theoretically. The output energy per pulse was ~60 mJ at peak power of ~50 kW. It was necessary to minimize not only harmful losses but also useful ones in both channels 00 0 1–02 0 0 and 02 0 0–0110 and to increase the input energy, i.e., the density of free electrons in the discharge, in order to increase the peak power and energy of 16-μm radiation. The highest values of peak power and energy of radiation were reached at different pressures of the active mixture. The rotational bottleneck effect limiting the peak power and energy of oscillation was important at rather low pressures of the active medium. Oscillation at the R12 line is more preferable than that at the P12 line for use as 9.6-μm dumping radiation.

Numerical calculations and experimental studies were used to show that the maximum overlap time of laser pulses in the two-wave mode of CO2 laser oscillation was achieved for the pair of rotational–vibrational lines whose weak-signal gain values were closest to each other.

We grew nonlinear crystals of the solid solutions GaSe 1– x S x (x ≤ 0.4) by the vertical Bridgman method. The increase in hardness from 8 kg/mm 2 for x = 0 to ~20 kg/mm 2 for x = 0.4 as a result of the presence of sulfur in the GaSe crystals allowed us to use a special technology to make working samples with position of the optic axis in the plane of the entrance surfaces, and for the first time to make direct measurements of the dispersion properties n e (λ) for the extraordinary wave and n o (λ) for the ordinary wave in the terahertz range of the spectrum by pulsed terahertz spectroscopy. We show that it is possible to realize an unconventional ee–e type of interaction in generation of terahertz radiation.

A differential absorption lidar based on a tunable TEA CO2 laser emitting at 42 lines of the 'hot' 0111 — 1110 band in the range from 10.9 to 11.4 μm is developed for detecting natural gas leakages from oil pipelines by measuring the ethane content in the atmosphere. The ethane detection sensitivity is 0.9 ppm km. The presence of methane does not distort the measurement results. The developed lidar can detect the natural gas leakage from kilometre heights at the flying velocities up to 200 km h-1 and a probe pulse repetition rate of 5 Hz.

We have built a wavelength-tunable CO2 laser meeting the requirements for low-intensity laser therapy. At λ = 10.57 μm and 9.24 μm, we observe a physiological effect detectable from the change in the extent of neurite outgrowth from sensory neurons. This makes it possible to study molecular mechanisms for interaction of low-intensity radiation with tissues in a living body. The ATP molecule is considered as the specific molecular target for the action of the radiation.

A widely used TEA CO2 laser system with UV preionization has been essentially modernized to obtain the CS2 molecule lasing. The output energy of 3 mJ on the transitions of the 0001-0200 band of CS2 molecule (wavelengths of lasing is about 14 microns) has been experimentally achieved. For the interpretation of experimental results and definition of the maximum power performances the numerical modeling has been carried out. The system of the balanced equations for densities of population of bottom vibrational levels of CS2 molecule and the first excited vibrational level of N2 molecule was solved. The calculations showed that for the selective cavity the lasing on a number of the other transitions of CS2, for example 0001-1000 (11.4 microns), 0001-0110 (38 microns), 0001-2000 (45.5 microns), 0001-1200 (117 microns) is possible also.

A widely used TEA CO2 laser system with UV preionization has been essentially modernized to obtain the CS2 molecule lasing. The output energy of 3 mJ on the transitions of the 0001-0200 band of CS2 molecule (wavelengths of lasing is about 14 microns) has been experimentally achieved. For the interpretation of experimental results and definition of the maximum power performances the numerical modeling has been carried out. The system of the balanced equations for densities of population of bottom vibrational levels of CS2 molecule and the first excited vibrational level of N2 molecule was solved. The calculations showed that for the selective cavity the lasing on a number of the other transitions of CS2, for example 0001-1000 (11.4 microns), 0001-0110 (38 microns), 0001-2000 (45.5 microns), 0001-1200 (117 microns) is possible also.

The THz CS 2 laser with the transversally electric discharge excitation (TE) has been created. The laser radiation with wavelengths of ~46 and ~39 microns (cascade transitions 00 0 1-20 0 0-20 0 0-11 1 0) with the total output energy ~1 mJ has been registered. Experimental and theoretical researches of some modes of lasering on these transitions have been carried out.

A widely used TEA CO2 laser system with UV preionization has been essentially modernized to obtain the CS2 molecule lasering. The output energy of 3 mJ on the transitions of the 00(0)1-02(0)0 band Of CS2 molecule (wavelengths of lasing is about 14 microns) has been experimentally achieved. For the interpretation of experimental results and definition of the maximum power performances the numerical modeling has been carried out. The system of the balanced equations for densities of population of bottom vibrational levels of CS2 molecule and the first excited vibrational level of N-2 Molecule was solved. The calculations showed that for the selective cavity the lasing on a number of the other transitions of CS2, for example 00(0)1-10(0)0 (11.4 microns), 00(0)1-01(1)0 (38 microns), 00(0)1-20(0)0 (45.5 microns), 00(0)1-12(0)0 (117 microns) is possible also.

We have measured absorption of emission from a TEA CO 2 laser, lasing on hot band lines, in pure CS 2 and a mixture of CS 2 with air, and we have determined the optimal lines for optical excitation. Numerical modeling has shown that as the peak intensity of the pump radiation is increased, we observe absorption saturation, the extent of which decreases as the pressure increases. The major factor responsible for absorption saturation is the “rotational bottleneck” effect. Depending on the peak intensity of the radiation, addition of a buffer gas can lead to an increase or decrease in the absorption.

CS2 laser with optical pumping has been offered for obtaining powerful T-rays. As a pumping source CO2 laser oscillating on the hot band (wavelength 11.4 mu m) has been used. Calculations have shown that at the optimal conditions the output 0.1 J at the peak power 1 MW can be obtained. The spectral tuning (2-3 THz) over the ro-vibrational lines is possible.

For obtaining powerful THz emission of radiation we offered to use CS/sub 2/ molecules pumping in the 10/sup 0/0-00/sup 0/1 channel by the radiation of TEA CO/sub 2/ laser working on lines of the 01/sup 1/1-11/sup 1/0 hot band (/spl lambda//spl sim/11.4 /spl mu/m). In this case THz radiation can take place in the 00/sup 0/1-12/sup 0/0 channel of CS/sub 2/ molecules (/spl lambda//spl sim/117 /spl mu/m). Our calculations show that for the pressure of the active medium /spl sim/0.1 atm (L/spl sim/1 m, V/spl ap/0.1 liter) and pumping energy 1 J output energy can achieve some tens mJ and the peak power >0.1 MW. The efficiency of transformation of the energy pumping into THz radiation can reach several percents.