The Experts below are selected from a list of 240 Experts worldwide ranked by ideXlab platform
Yasutoshi Ishihara - One of the best experts on this subject based on the ideXlab platform.
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Photoacoustic depth profiling of a skin model for non-invasive glucose measurement
2008 30th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2008Co-Authors: Naoki Wadamori, Ryou Shinohara, Yasutoshi IshiharaAbstract:A measurable depth of the blood glucose level by using photoacoustic spectroscopy (PAS) was discussed experimentally in order to improve detection sensitivity. Since a measurable depth of the PAS depends on a modulation frequency of the chopped light irradiated to a sample, the relationship between modulation frequency and the thickness of a sample was evaluated. The photoacoustic detector used in these experiments consisted of an acoustic resonance pipe and an optical microphone, and a two-layer model composed of silicone sheets with the different optical absorption. The measurable depth was 2–3 mm with modulation frequency of 1000–2000 Hz. Furthermore, the reason for the measurable depth to be deeper than the Thermal Diffusion Length of the sample was discussed theoretically. From these analyses of thermoelastic wave, the relation between the photoacoustic signal propagation and the measurable depth in a tissue was clarified.
Klaus Zimmer - One of the best experts on this subject based on the ideXlab platform.
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Sub-micron periodic structuring of sapphire by laser induced backside wet etching technique.
Optics express, 2007Co-Authors: Stavros Pissadakis, Rico Böhme, Klaus ZimmerAbstract:The periodic structuring of sapphire, by using laser induced backside wet etching technique (LIBWE) and 266 nm, 150 ps Nd:YAG laser radiation, is demonstrated here for first time. Sub-micron period Bragg reflectors are successfully patterned in sapphire wafers using modest energy densities and number of pulses. The gratings are characterized using diffraction efficiency measurements, AFM, and SEM. Issues related to the ablation process and to the phase mask holography are presented and discussed. The experimental results presented depict that the applied method is capable to produce relief structures of depth as deep as 100 nm, while maintaining high resolutions, close to the Thermal Diffusion Length of the material corresponding to the ultrashort pulse duration.
Andreas Mandelis - One of the best experts on this subject based on the ideXlab platform.
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Impulse PhotoThermal Evaluation of Materials Via Frequency Modulated Optical Reflectance II: Experimental
Review of Progress in Quantitative Nondestructive Evaluation, 2014Co-Authors: Joan F. Power, Andreas MandelisAbstract:Recently, a powerful method of photoThermal detection was reported which enabled Thermal wave imaging to be carried out on micron sized structures in semiconductors [1,2]. The new method utilized the photoThermally induced modulation of the sample’s surface optical reflectivity to detect Thermal wave phenomena at bandwidths exceeding 10 MHz. The wide bandwidth capabilities of the method enabled very shallow structures to be analyzed in semiconducting materials because of the relationship that exists between the modulation frequency of the excitation beam and the Thermal Diffusion Length.
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Temperature Effect on PhotoThermal Reflectance Signal: Application to Ion Implanted and Amorphous Silicon
Photoacoustic and Photothermal Phenomena II, 1990Co-Authors: Constantinos Christofides, I. A. Vitkin, Andreas MandelisAbstract:PhotoThermal reflectance study as a function of temperature of processed silicon (crystalline, ion-implanted, amorphous) has been performed for the first time. The influence of the substrate on the observed signal has been examined in the light of the temperature and modulation frequency dependence of the Thermal Diffusion Length.
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PhotoThermal reflectance investigation of processed silicon. II. Signal generation and lattice temperature dependence in ion‐implanted and amorphous thin layers
Journal of Applied Physics, 1990Co-Authors: I. A. Vitkin, Constantinos Christofides, Andreas MandelisAbstract:PhotoThermal reflectance investigations as a function of temperature of various forms of silicon (crystalline, ion‐implanted, amorphous) are reported largely in the Thermal wave regime (low‐modulation frequencies and large laser beam spot sizes). The observed results have been explained by a Thermal wave model that has been extended to include the effect of lattice temperature. The influence of substrate on the observed signal has been examined in light of the temperature and frequency dependence of the Thermal Diffusion Length. The possible application of the technique to depth‐profiling studies, and to the investigation of ion‐implanted semiconductors, is discussed.
Lionel Bertrand - One of the best experts on this subject based on the ideXlab platform.
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Advantages of Phase Analysis in Fourier Transform Infrared Photoacoustic Spectroscopy
Applied Spectroscopy, 2016Co-Authors: Lionel BertrandAbstract:Fourier transform infrared photoacoustic spectroscopy is greatly improved by the simultaneous measurement of the photoacoustic signal amplitude and phase. Saturation effects, sample dilation, and optical scattering, even in heterogeneous samples, can be easily corrected to give the absorption coefficient real value. Quantitative analyses without any special sample preparation or special photoacoustic cell are now possible. Moreover, the phase of the photoacoustic signal permits depth localization of the absorbing species within the Thermal Diffusion Length. Surface analyses are thus possible that have a depth resolution at least one order of magnitude higher than that obtained by changing the Thermal Diffusion Length. In this paper we illustrate the advantages of phase analysis in Fourier transform infrared photoacoustic spectroscopy with the detection of sorbed water in polyethylene.
Henry H. Mantsch - One of the best experts on this subject based on the ideXlab platform.
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FT-IR photoacoustic depth profiling spectroscopy of enamel
Calcified Tissue International, 1994Co-Authors: Michael G. Sowa, Henry H. MantschAbstract:Photoacoustic Fourier transform infrared (PA-FT-IR) depth profiling spectra of the enamel of an intact human tooth are obtained in a completely nondestructive fashion. The compositional and structural changes in the tissue are probed from the enamel surface to a depth of about 200 μm. These changes reflect the state of tissue development. The subsurface carbonate gradient in the enamel could be observed over the range of about 10–100 μm. The carbonate-to-phosphate ratio increases in the depth profile. The depth profile also reveals changes in the substitutional distribution of carbonate ions. Type A carbonates (hydroxyl substituted) increase relative to type B carbonates (phosphate substituted) with increasing Thermal Diffusion Length. In addition to the changes in the carbonate ion distribution and content, the PA-FT-IR depth profile clearly indicates a dramatic increase in the protein content relative to the phosphate content with increased depth. The changes in the carbonate content and distribution, along with the changes in the protein content, may be responsible for the changes observed in the apatitic structure in the depth profile of the enamel.