CO2 laser-tissue interaction was investigated by the autodyne detection method of backscattered radiation. Doppler spectra obtained in the course of pulse ablation of various pig tissues in vitro are presented. The interrelation between these spectra and some properties of biotissues was established. The possibility of the instants of time determination of the laser radiation passage through the demarcation line of biotissues is demonstrated.
The correlation between Doppler spectra due the emission of tissue destruction products at laser ablation and tissue types was established. The possibility of biotissue type relative determination at the passage of CO2 laser beam through various sequences of tissue layers is demonstrated.
A procedure of operational inspection of laser technological processes has been suggested that is based on measuring spectral properties of Doppler signal of backscattering from the interaction region by optical heterodyne technique. The technique enables us to obtain the qualitative and quantitative information on hydrodynamic flows in reactor. The measurements have been performed with about 1 kW/cm2 beam intensity of continuous-wave carbon- dioxide laser at the surface of a number of condensed substances by monostatic scheme of interaction.
The theoretical basis for wind velocity field parameters' measurements using CW Doppler Lidars (DL) is outlined. The instant power spectrum of photocurrent is shown to be histogram of velocity projection field with a weight depending on Dl's parameters. A non-destructive long-range method is presented for measuring the structure constant of the wind velocity field. The essence of the method is (the constancy of the backscatter coefficient is assumed): the average square width of the DL photocurrent power spectrum is the averaged structure function of the wind velocity weighted with a function depending on the DL parameters, the measurement time and the average wind velocity. Consequently, it is proportional to velocity structure constant with a factor depending on the DL parameters, the measurement time, the average wind velocity, the internal and external scales of turbulence. At certain DL parameters and measurement time the factor is shown to be practically independent from the average wind velocity, the internal and external scales of turbulence, thus a priori estimate can be successfully used instead of their real values. The differences between structures of CW and pulsed DL signal are discussed. The described above method is applied for pulsed DL.
We have developed two coherent lidar systems based on cw and TEA CO2 lasers. The lidars have been tested and applied for the atmospheric wind velocity measurements. We have elaborated and experimentally verified a new method of nondestructive long-range measurement of the parameters of the atmospheric turbulence with a cw Doppler lidar (DL). The method is based on certain processing of the heterodyne Doppler spectra. In addition to the wind velocity magnitude, the method yields the value of the velocity structure constant. The method has been experimentally verified. Some results of applications of the DL for detecting artificially generated vortexes (aircraft traveling vortexes) and distinguishing them from natural winds and turbulence based on a comparison of the magnitudes of the velocity structure constant are presented.
The kinetic-cooling effect of a CO2-N2-He gas mixture on the cell placed within a laser cavity is here used as the basis of a scheme for chirp-compensation in an injection-locked TEA CO2 laser. The cooling of the gas is a result of its irradiation by the laser pulse. A kinetics model has been developed in order to determine both temperature and refractive index on the basis of detailed vibrational relaxation kinetics
Doppler lidars are prospective means for long-range measurements of wind velocity in the atmosphere, based on the registration of Doppler frequency shifts in the radiation backscattered by moving aerosol particles. The development of coherent lidar systems based on CW and TEA CO2 and on Nd:YAG lasers is presented. Test results from the application of these lidars to atmospheric wind velocity measurements are discussed.