Optical saturation effects in photothermal spectroscopy

Abstract

The dependence of the fundamental and harmonic photothermal (PT) signals on the intensity I₀ of the illumination source is analyzed. It is found that the PT signal does not indefinitely increase with I₀, but at sufficiently high power densities begins to decrease as 1/I₀. The onset of optical saturation thus defines an upper limit to the sensitivity of spectrometers based on photothermal detection.