Separation of optical thin-film and substrate absorption by means of photothermal surface deformation technique

The photothermal surface deformation (PTD) technique is shown to be feasible to separate absorption losses of single-layer film and substrate absorption from each other by a completely contactless detection of the thermoelastic sample response only appropriately varying the focus radius of the heating beam. This offers a method for a depth-resolved distinction of absorptive regions within a layered structure by the help of lateral resolved PTD absorption measurements. Additionally, both the sensitivity and feasibility of the apparatus is demonstrated by selected results at 10.6 μm.