Andrian I. Kouznetsov

Mechanisms of optical losses in polycrystalline fibers

Different mechanisms of extrinsic losses, including aging, in extruded mixed AgClxBr1-x fibers are discussed. Additional losses caused by changes in structure of fiber material have been investigated.

Multicomponent gas analyzers based on tunable diode lasers

A family of multicomponent gas analyzers based on tunable diode lasers (TDL) are presented including an open optical path 3-component gas analyzer for monitoring atmosphere pollution; a 4-gas component analyzer with a multipass cell, a multichannel TDL system with multipass cell and MIR fiber optics delivery, and a multichannel TDL analyzer for breath content gas analysis. A4B6 tunable diode lasers of different spectral region form 4 to 12 micron were used in every channel of the analyzers to obtain atmospheric transmission spectra and to measure concentration of studied gases. Main gaseous atmospheric pollutants like CO, NO, NH3, CH4, SO2, etc. and some of breath gases could be measured at ppb concentration level in real time with these systems depending on customers requirements. The analyzers are driven by IBM compatible PC. The first results on field monitoring tests as well as on their application to human exhalation content analysis and human exposure monitoring are presented.

Tunable diode laser spectroscopy accessories based on middle IR halide and chalcogenide fibers

The use of mid-IR fiberoptic components in spectroscopy and analysis using A4B6 tunable diode lasers has been studied, and the results are reported. Spectral parameters of the fibers and complete spectroscopic systems based on the fibers and Pb-salt diode lasers are presented. The further development of the presented systems for applications in remote monitoring, multicomponent gas mixtures analysis, and evanescent wave spectroscopy of gases is addressed.

Infrared diode laser chemical sensors with multipass cell based on silver halide and chalcogenide fibers

A high sensitive chemical analyzer of molecular gases is presented. Its based on measurements of high resolution molecular absorption spectra obtained with infrared tunable diode lasers (TDL). To transmit radiation from lasers to an analytical cell and back to detectors, infrared fibers with low optical losses are used. A multipass optical cell is used to enhance the essential sensitivity of the sensor. Various gaseous molecular objects could be detected by this analyzer due to the wide spectral range of available TDLs and fibers. Use of fibers for laser transfer could provide remote monitoring and multicomponent mixture analysis and evanescent spectroscopy of gases in the near future.

Applications of tunable diode laser spectroscopy for the detection of exhaled endogenous gases: CO, NH3, CH4, N20, and CO2

Tunable diode laser spectroscopy (TDLS) is proposed for content measurements of trace gases like CO, carbon-dioxide, NH3, CH4, NO, NO2 in human and animals exhalation. High sensitivity and wide dynamic range of the method ensure fast detection of these gases at ppb level and within the accuracy better than 10%. One-expiration sample is enough to reach these parameters. There is no need for any preliminary preparations of tested samples. Some pairs of the gases, for instance, CO and carbon-dioxide, NH3 and carbon- dioxide, or CO and nitrous oxide, can be measured simultaneously by one laser providing complex studies. The high sensitive gas analysis could provide necessary background to the noninvasive diagnostics in a wide variety of medical problems. Perspectives of the TDLS methods in application to medicine diagnostics are demonstrated by the first results of exhalation tests.

Detection of small trace molecules in human and animal exhalation by tunable diode lasers for applications in biochemistry and medical diagnostics

Tunable diode laser spectroscopy (TDLS) is proposed for content measurements of trace gases like CO, CO2, NH3, CH4, NO, NO2 in human and animal exhalation. High sensitivity and wide dynamic range of the method ensure fast detection of these gases at ppb level and within the accuracy better than 10%. One-expiration sample is enough to reach these parameters. There is no need for any preliminary preparations of tested samples. Some pairs of the gases, for instance, CO and CO2, NH3 and CO2 and CO and N2O, can be measured simultaneously by one laser providing complex studies. The high sensitive gas analysis could provide necessary background to the noninvasive diagnostics in a wide variety of medical problems. Perspectives of the TDLS methods in application to medicine diagnostics are demonstrated by the first results of exhalation tests.

Human expiration content diagnostics by tunable diode lasers in middle infrared

Results on the application of tunable diode laser gas analysis to determining the trace components of human breath are presented. Schemes of the analyzers specially developed for measurement of both carbon oxides in expiration are described. A few results illuminating possible applications of TDL in high sensitive medical diagnostics have been obtained. For nonsmokers, the expired concentration of CO is slightly higher than inhaled air. Specific surplus value depends on the persons age. The surplus CO content increased significantly just after intensive physical exercises like jogging. For smokers, the farmacokinetical curve of abundant CO removal from the organism could be investigated. The smoking status of tested individuals becomes easy available. Breath-hold simultaneous measurements of CO and CO2 have shown the difference in the dependencies of their concentrations on breath-holding time. The possibility to investigate phenomena like molecular pulmonary diffusion of the alveolar-capillary membrane and an organisms compensation reactions to oxygen shortage seems to become real. Perspective leads for development and the application of diode laser spectroscopy methods to the analysis of gaseous microimpurities in medicine are also discussed.

Middle-infrared fiber optic accessories for molecular spectroscopy and gas analysis with tunable diode lasers

A highly sensitive chemical analyzer of molecular gases is presented. It is based on measurements of molecular absorption in high resolution spectra obtained with infrared tunable diode lasers (TDL). To transmit radiation from lasers to an analytical cell and back from the cell to detectors, infrared fibers with low optical losses are used. A multipass optical cell is used to enhance a sensitivity of the sensor. Various gaseous molecular objects could be detected by this analyzer due to wide spectral range of available TDLs and fibers. Use of fibers for laser radiation transfer could provide remote monitoring, multicomponent mixture analysis, and evanescent wave spectroscopy of gases in the near future.

Monitoring of rapid blood pH variations by CO detection in breath with tunable diode laser

Detection of endogenous carbon monoxide content in breath with tunable diode lasers (TDL) was proposed for noninvasive monitoring of rapid blood pH variation. Applied approach is based on high sensitivity of the haemoglobin and myoglobin affinity for CO to blood pH value and an ability to detect rapidly small variations of CO content in expired air. Breath CO absorption in 4.7 micrometers spectral region was carefully measured using PbSSe tunable diode laser that can provide 1 ppb CO concentration sensitivity and 10 s time constant. Applied TDL gas analyzer was used to monitor expired air of studied persons in physiological tests including hyperventilation and physical load. Simultaneous blood tests were conducted to demonstrate correlation between blood and breath chemical parameters.

Multicomponent fiber optic gas sensor based on MIR tunable diode lasers

Within the framework of this studies development of a model of a functional multicomponent highly sensitive new generation analyzer, designed to measure 2 to 4 gas components in a mixture, was proposed. This model will become a prototype for a whole new family of analyzers, which will differ from one another by their particular set of detected gases and sensitivity depending on task requirements. The gas detecting analyzers utilise the principles of high resolution absorption spectroscopy, possibly by utilising a tunable diode lasers (TDL) in the IR range. By using a laser spectral method for measuring, it ensures high sensitivity, accuracy, selectivity and fast time response in recording. The distinguishing aspect in the development of the analyzer is the design and schematic based on the use of MIR-fiber optics with low optic losses. Hence, it is possible to have the unit in a small geometric volume with instrumentation for a multichannel measuring optical track, and a simplified cryostatic system for IR lasers and photodetectors. With the help of a highly sensitive, fast tune responding analyzer based on tunable diode lasers, molecular gases, having absorption bands in the IR range, can be measured. Detection of molecules like CO, CO2, NO, NO2, N20, H2S, SO2, NH3, H20, H2O2, CH4, C2H2, C2H4, HF, HC1, HCN, freons and many others is possible using this technique. These multicomponent gas sensors can be applied as a diagnostic tool in scientific investigations, in physics, chemistiy and biochemistry, in ecology - for recording atmospheric pollutants, in medicine - diagnosing illnesses and screen tests as well as in industiy - trace chemical technology and burning processes. These systems can be also used as a reference tool for calibration of less sensitive and less precise gas analyzers used in routine monitoring.