Ti:Al2O3 laser pumped by radiation from a copper-vapor laser

A scheme enabling spatial matching of copper-vapor laser radiation, which pumps a mode of an Al₂O₃:Ti laser cavity, has been developed and implemented. It is shown that copper vapor lasers as pump sources for titanium-sapphire lasers are fully capable of competing with conventional pump sources. Pis’ma Zh. Tekh. Fiz. 25, 6–11 (September 26, 1999)     

Laser remote sensing of atmospheric ammonia using a CO2 lidar system

A CO2 differential-absorption lidar system has been used for the remote sensing of ammonia in the atmosphere. For CO2 lidar returns backscattered from topographic targets at ranges up to 2.7 km, the path-averaged sensitivity of the DIAL system was 5 ppb of NH3 . Concentrations of atmospheric ammonia were found to vary during the day from undetectable levels (<5 ppb) to as high as 20 ppb, depending on temperature and humidity conditions.     

Prediction model for determining the optimum operational parameters in laser forming of fiber-reinforced composites

Composite materials are widely employed in various industries, such as aerospace, automobile, and sports equipment, owing to their lightweight and strong structure in comparison with conventional materials. Laser material processing is a rapid technique for performing the various processes on composite materials. In particular, laser forming is a flexible and reliable approach for shaping fiber-metal laminates (FMLs), which are widely used in the aerospace industry due to several advantages, such as high strength and light weight. In this study, a prediction model was developed for determining the optimal laser parameters (power and speed) when forming FML composites. Artificial neural networks (ANNs) were applied to estimate the process outputs (temperature and bending angle) as a result of the modeling process. For this purpose, several ANN models were developed using various strategies. Finally, the achieved results demonstrated the advantage of the models for predicting the optimal operational parameters.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-020-00304-3     

Raman lidar for remote sensing of sulfur-containing hydrocarbons in the atmosphere

It is demonstrated that remote detection of the maximum permissible concentrations of dangerous substances (hydrogen sulfide, mercaptan, ethylmercaptan) is possible only at inadmissibly short distances.     

Laboratory analysis of techniques for remote sensing of estuarine parameters using laser excitation

The theoretical concepts underlying remote sensing of estuarine parameters using laser excitation are examined. The concepts are extended to include Mie scattering as a measure of the total suspended solids and to develop the water Raman signal as an internal standard. Experimental validation of the theory was performed using backscattered laser light from a laboratory tank to simulate a remote-sensing geometry. Artificially prepared sediments and biological cultures were employed to check specific aspects of the theory under controlled conditions. Natural samples gathered from a variety of water types were also analyzed in the tank to further enhance the simulation. The results indicate that it should be possible to remotely quantify total suspended solids, dissolved organics, attenuation coefficient, chlorophyll a, and phycoerythrin in estuarine water using laser excitation.     

Design and performance of a multiwavelength airborne polarimetric lidar for vegetation remote sensing

The University of Nebraska has developed a multiwavelength airborne polarimetric lidar (MAPL) system to support its Airborne Remote Sensing Program for vegetation remote sensing. The MAPL design and instrumentation are described in detail. Characteristics of the MAPL system include lidar waveform capture and polarimetric measurement capabilities, which provide enhanced opportunities for vegetation remote sensing compared with current sensors. Field tests were conducted to calibrate the range measurement. Polarimetric calibration of the system is also discussed. Backscattered polarimetric returns, as well as the cross-polarization ratios, were obtained from a small forested area to validate the system's ability for vegetation canopy detection. The system has been packaged to fly abroad a Piper Saratoga aircraft for airborne vegetation remote sensing applications.     

Modeling the optimal parameters for a remote sensing device

We propose a computer model for a device for remote sensing of the underlying surface close to a gas pipeline, allowing us to calculate the ladar parameters so we can select their optimal design values and work up recommendations for remote sensing from on board an aircraft.     

Selection of optimum parameters for a filter at the output of a transducer

Conclusions The above computation method of optimum filters for transducers provides a substantiated compromise solution which satisfies two contradictory requirements, consisting of the quality in smoothing out the ripple, on the one hand, and the quality of transmitting the information spectrum of the signal on the other hand. This technique can be applied for obtaining design formulas for optimum parameters not only of a single section RC filter, but also for more complicated filters.     

Line-pair selections for remote sensing of atmospheric ammonia by use of a coherent CO2 differential absorption lidar system

Research on wavelength selection of CO2 laser lines for range-resolved remote sensing of atmospheric ammonia by use of a coherent differential absorption lidar system is described. Four laser line pairs are suggested for different levels of ammonia concentrations from approximately a few parts per billion to 1 part per million in a polluted atmosphere. The most suitable line for measuring ambient ammonia concentrations is 9R(30), because it has the highest absorption coefficient. 10R(14) has the lowest absorption coefficient, making it suitable for strong source mapping. 10R(8) and 10P(32) are best for intermediate levels of ammonia concentration. Absorption coefficients of ammonia calculated from the HITRAN96 database are in good agreement (mostly within +/-10% )with other experimental results.Sensitivity of measurement, interference from water-vapor lines with typical humidity in the summer,and sensitivity of ammonia absorption cross section to temperature and pressure are analyzed and calculated for the four wavelength pairs. The results show that the interference from water-vapor lines is easily correctable to a negligible amount, and errors caused by uncertainties in temperature and pressure are insignificant.     

Methods and devices for measuring the parameters of probing beams

Translated from Izmeritel'naya Tekhnika, No. 7, pp. 50–52, July, 1991.     

Analytical estimation of the parameters of autodyne lidar

An analytical approach for a calculation of the parameters of autodyne lidar is presented. Approximate expressions connecting the absorption coefficient and the distance to the remote target with both the lidar parameters and the measured quantities are obtained. These expressions allow one to retrieve easily the information about the atmosphere from the experimental data.     

Pulsed laser deposition of NiTi shape memory alloy thin films with optimum parameters

A series of experiments was carried out to optimize the pulsed laser deposition parameters for the fabrication of high quality NiTi shape memory alloy thin films. Smooth NiTi shape memory alloy thin films were deposited at high growth rate with optimum deposition parameters based on the analysis of the relationships among the morphology of the target surface and the deposited thin film, the laser energy, the target–substrate distance, the thin film composition and its growth rate. Crystal structures and phase transformation temperatures of the annealed Ni_49.7Ti_50.3 thin film were characterized by using X-ray diffraction and differential scanning calorimetry, respectively. The martensitic transformation temperature of the crystallized Ni_49.7Ti_50.3 thin film is found to be lower than room temperature and 27°C lower than that of the NiTi target material. These results are attributed to the refined grain size of the thin film and its composition, which deviates slightly from Ni₅₀Ti₅₀.     

Femtosecond laser radiation frequency converters for lidar monitoring of the atmosphere

The possibility of using biaxial nonlinear crystals in the optical converters of femtosecond radiation pulses for laser sounding of the atmosphere has been studied. A method of broadband monitoring of the atmosphere composition using the differential optical absorption spectroscopy technique is described. The results of the numerical simulation of the lidar monitoring of gaseous components of the atmosphere using frequency-converted femtosecond laser radiation pulses are presented.     

Interferometer using a laser pointer for remote microdisplacement measurements

A portable Michelson interferometer for remote optical sensing with imaging capability is developed based on a laser pointer and experimentally studied. The setup has an open sensing arm with a mirror that can be attached to any object for the measurement of responses such as microdisplacement, strain, stress, and temperature. A mirror in the reference arm is mounted on an encoded stepper motor, which can operate under remote control via Web/Internet for reset and calibration. Remote microdisplacement measurements precise to within 5 μm have been performed.     

Remote laser probing of hydrocarbons in the atmosphere

A lidar equation for the Raman backscattering of light from molecules of some hydrocarbons was numerically solved. The optimum value of the copper vapor laser wavelength for the probing of hydrocarbons at a distance from 40 m to 4 km was determined.     

Simplified calculations for accuracy of a lidar dial system to measure atmospheric H2O vapor and temperature

A simple method is given for computing the relative errors in H2O vapor and T (temperature) profiles measured by a ground-based differential lidar system: The analysis is based on a simplified model of the earth's atmosphere, which allows one to write exact mathematical expressions for the lidar return signals which can be evaluated in closed form. Error computations can be made from these expressions with a small pocket calculator to an accuracy of a few percent. Error estimates are given for a lidar system used to measure H2O and T profiles from the ground up to a 5-km altitude. The results are given for an ideal system with no instrument noise and for a system using quantum detectors with detector-amplifier noise and less than unity quantum efficiency. The relative merits of the photomultiplier tube and silicon diode as detectors are also assessed using this technique of error analysis. Regions of useful operation for these detectors are defined in terms of the signal energy of the lidar return and the noise equivalent power of the detector.     

Determination of plasma parameters with a probing magnetic field pulse

An experimental technique for the determination of electric conductivity and temperature of plasma is presented. The technique is based on comparing the signals that are produced by a pulsed magnetic field in the circuits of two probes located within the studied plasma and outside of it. The proposed technique for the measurement of plasma parameters was tested experimentally in the context of measuring the electric conductivity and temperature of plasma flux formed in cathode spots of a high-current pulsed vacuum arc with a magnesium cathode.