The sensitivity of thermal-lens and phase-shift (interferometric) techniques in photothermal spectroscopy: A comparative study

Abstract

The thermal-lens and phase-shift (interferometric) techniques of photothermal spectroscopy are studied theoretically for the coaxial and mutually orthogonal propagations of probing and pumping beams. Respective expressions for the amplitude of detected signals are derived for the case of the volume absorption of pumping radiation. The sensitivities of the two techniques are numerically analyzed for different parameter values. It is demonstrated that the phase technique offers higher sensitivity especially if the size of the region with a perturbed temperature field is much larger than the probing beam radius.