Aerogel foil plasma: Forward scattering, back scattering, and transmission of laser radiation

Experimental results obtained with “Kanal-2” facility under the study of powerful laser pulse interaction with the low density microstructure media are presented and discussed in this paper. Forward scattering, back scattering, and transmission of laser radiation by aerogel foil plasma have been investigated. The temporal, spectral, and energy characteristics of both the radiation scattering in the direction of heating radiation beam and the back scattering radiation were studied; the directional diagrams of forward and back scattering radiation were obtained for ω0 and 2ω0 frequencies. Analysis of intensity redistribution on the heating beam cross-section after passing through a polymer microstructure target was carried out.

Temperature Measurement of Single Levitated Microparticles Using Stokes/Anti-Stokes Raman Intensity Ratios

A method has been developed to determine the temperature of single microparticles levitated in an electrodynamic balance. Particle temperatures were ascertained from the measured intensities of the Stokes and anti-Stokes Raman spectra. Temperatures near ambient were obtained for titanium dioxide and calcium nitrate microparticles with the use of a Raman-based calibration of the optical system to correct for wavelength-dependent effects. Higher temperatures were also measured with the use of a carbon dioxide infrared laser to electromagnetically heat the particle. In an effort to minimize particle instabilities caused by the heating beam, the Gaussian intensity profile of the beam was modified with an axicon beam expander to produce a doughnut-like intensity distribution. The temperature measurement technique and quantitative Raman composition analysis were applied to study dehydration of a calcium nitrate tetrahydrate particle.

Low-absorption measurement of optical thin films using the photothermal surface-deformation technique

The purpose of this paper is to show both theoretically and experimentally the feasibility of the photothermal surface-deformation (PTD) technique for a highly sensitive, completely contactless detection, as well as a lateral and depth-resolved localization, of absorption in optical thin films. Peculiarities in the interpretation of the measuring signal, such as the influence of the thermal-expansion coefficient of the substrate and the focal diameter of the heating beam, have been pointed out.As a relevant example, the absorption of evaporated ZrO2, single layers on BK 7 substrates has been measured at λ = 515 nm. Their bulk absorption is shown to be strongly influenced by both deposition parameters and the baking procedure.