Absorbance Measurements in Optically Inhomogeneous Samples Using Phase-Conjugate Thermal Lens Spectroscopy

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Abstract
The optical phase conjugation properties of a BaTiO3 crystal are employed in a thermal lens experiment to measure small absorbance values of optically inhomogeneous samples. The sensitivity of the thermal lens, together with the beam reconstruction capabilities of phase conjugation, allows measurement of absorbances as low as 1.2 × 10−5 in the presence of large-amplitude spatial noise. A model which describes the behavior of an ordinary thermal lens could be used to evaluate the behavior of the phase-conjugate thermal lens response. Controlled phase-front perturbations generated by the thermal lens are used to characterize the influence of optical path distortions on phase-conjugate reflectivity.