| The viability of measuring Fourier transform infrared (FTIR) spectra of various samples with a sample-contact method of photothermal detection has been explored, with the goal of evaluating this method for application to a novel fiber optic-based probe/sensor design for infrared detection and spectroscopy. Presented here are the proof of principle experiments for photothermal detection in a sample-contact geometry via photothermal beam deflection (PTBD) in a solid deflection medium. These experiments were designed to evaluate the advantages over reflectance and transmission methods of detection that are currently used in sample-contact, fiber-optic FTIR probes. Several infrared transparent solid deflection media have been evaluated in PTBD, including BaF2, KBr, Moissanite, sapphire, ZnS, and ZnSe. Comparison of these materials indicates that ZnSe and ZnS are the best prospects for use in the proposed probe design. The versatility of sample analysis with PTBD using solid deflection media has been demonstrated for liquid, powder, and polymer film samples. In addition, the first demonstration of solid deflection PTBD for discrete depth profiling is presented here for layered polymer samples of various types. Two methods of detection were evaluated in terms of a near-field signal enhancement with the prospect of future miniaturization of the PTBD experiment. Finally, these results are scrutinized in terms of the future creation of a fiber-optic PTBD probe. |
