Theory for laser-induced photothermal refraction

Abstract

Photothermal refraction Is a novel thermooptlcal technique which produces a linear measure of sample concentration and absorptivity with high sensitivity and spatial resolution. In this technique, a cylindrical thermal lens Is formed within a sample from absorption of a chopped Gaussian laser beam. The lens Is Interrogated at right angles with a continuous wave probe laser beam and detected as a change In the far-right probe beam center Intensity. This paper develops a theoretical analysis of photothermal refraction.

Microfluidics and Integrated Optics Glass Sensor for In-Line Microprobing of Nuclear Samples

“…The pump laser beam can be described by a Gaussian intensity profile [16]: (5) where is the waist of the beam and is the beam power. If we assume a constant beam waist inside the channel, the radial temperature distribution as a response to a short laser pulse of energy and duration is given by: (6) where • analyte absorptivity, cm • • and .…”

The Theory of Photothermal Effect in Fluids

“…In this section, expressions for the change in intensity of a probe laser passing through a thermal lens will be derived (Fang and Swofford, 1983;Harris and Dovichi, 1980;Dovichi, Nolan, and Weimer, 1984). The thermal lens, of course, is created by the nonuniform refractive index, which is caused by the absorption of the pump beam.…”

Photothermal Techniques in Material Characterization Applications

“…Many applications of PBR schemes have been developed, e.g., high-sensitivity spectroscopy (Kliger [12], Boccara et al [13), Jackson et al [14], Bialkowski [15]) and imaging (for example, Dovichi et al [16]). Theoretical interpretations of the PBR signals for PT monitoring have also been extensively developed, e.g., analytical solutions for simple and typical cases are given by Tam [3], while more general cases of PBR has been done by numerical computations (Rose et al [17]) or by ray-tracing (Sell [18]).…”