Radiofrequency impedance monitoring of the biological tissues under local heating by optical radiation.

Development of methods for simultaneous control of state of biological tissues during optical treatment is the important tasks in laser surgery. We introduce a novel approach for the monitoring of the state of biological tissues in the process of its local heating by optical radiation. It is based on measurements of the electrical radiofrequency impedance kinetics of the sample during irradiation.

Radiofrequency impedance spectroscopy of biological tissues under heating by homogeneous laser radiation.

We have developed an original method to measure the temperature dependence of the biological tissue electrical properties based on its heating by homogeneous optical radiation.The conventional approach in hyperthermia research involves heating due to a thermal conductivity through the surface of the sample. The novel technique is based on the emission of heat sources in the sample volume caused by the absorption of optical radiation.

Acoustic resonance laser calorimetry for measurements of low optical absorption.

A novel method of acoustic resonance laser calorimetry (ARLC) for the determination of low optical absorption coefficients of crystals and glasses is introduced. It is based on measurements of the kinetics of the equivalent temperature of the sample irradiated by the pulse laser radiation. The equivalent temperature of the sample is directly obtained by measuring the frequency changes of its temperature-calibrated acoustic resonances excited by the laser radiation with a corresponding pulse repetition rate.

Accurate measurements of longitudinal temperature distribution of PPLN crystal in the process of second-harmonic generation.

Phase-matching temperature tuning curves and longitudinal temperature distribution of periodically poled lithium niobate (PPLN) crystal were measured in the process of second-harmonic generation (SHG) of 1070 nm pump wavelength using tiny transparent piezoelectric crystals as the temperature sensors. The temperatures of the crystal sensors placed along the PPLN length were determined directly by measuring the induced frequency shifts of their piezoelectric resonances, which were excited in a noncontact manner by a probe radio-frequency electric field. Such temperature sensors do not suffer additional heating conditioned by absorption of scattered radiation and also do not have any contact wires.

Anisotropy of nonlinear optical absorption of LBO crystals at 355 nm.

The dependence of the nonlinear optical absorption coefficients on the intensity and polarization of pulsed laser radiation at 355 nm was investigated for lithium triborate (LBO) crystals using the piezoelectric resonance laser calorimetry.

Interferometric technique for investigation of nonradiative transition kinetics in silica-fiber laser media.

A novel tool for investigation of nonradiative processes in active solid-state laser media is proposed. The technique is based on using an interferometer for population-kinetics detection by means of resonantly enhanced nonlinearity. The advantages of this method in comparison with traditional luminescence-kinetics techniques are verified on the example of decay time measurements for nonradiative 4I(11/2)→4I(13/2) transition in an Er3+-doped active optical fiber.