Abstract

The laser photopyroelectric effect measures an optical absorption depth profile in a thin film through the spatial dependence of a heat flux source established below the film surface by light absorption from a short optical pulse. In this work, inverse depth profile reconstruction was achieved by means of an inverse method based on the expectation-minimum principle (as reported in a companion paper), applied in conjunction with a constrained least-squares minimization, to invert the photopyroelectric theory. This method and zero-order Tikhonov regularization were applied to the inversion of experimental photopyroelectric data obtained from samples with a variety of discrete and continuous depth dependences of optical absorption. While both methods were found to deliver stable and accurate performance under experimental conditions, the method based on the constrained expectation-minimum principle was found to exhibit improved resolution and robustness over zero-order Tikhonov regularization.

Photopyroelectric thermal-wave tomography of aluminum with ray-optic reconstruction

Mahendra Munidasa and Andreas Mandelis
J. Opt. Soc. Am. A 8(12) 1851-1858 (1991)

Frequency-modulated impulse response photothermal detection through optical reflectance. 1: Theory

Andreas Mandelis and Joan F. Power
Appl. Opt. 27(16) 3397-3407 (1988)

Frequency-modulated impulse response photothermal detection through optical reflectance. 2: Experimental

Joan F. Power and Andreas Mandelis
Appl. Opt. 27(16) 3408-3417 (1988)

Depth profiling of laser-heated chromophores in biological tissues by pulsed photothermal radiometry

Thomas E. Milner, Dennis M. Goodman, B. Samuel Tanenbaum, and J. Stuart Nelson
J. Opt. Soc. Am. A 12(7) 1479-1488 (1995)

Nondestructive depth profiling of ZnS and MgO films by spectroscopic ellipsometry

K. Vedam, S. Y. Kim, L. D'Aries, and A. H. Guenther
Opt. Lett. 12(7) 456-458 (1987)