Re-usable PDMS stamps for non-destructive fluorescence evaluation and imaging of thin film photonic structures.

We report on a non-destructive method for evaluating fluorescence emission from fluorophores placed upon engineered photonic structures. Our method utilizes re-usable, fluorescent thin film coated polydimethylsiloxane (PDMS) stamps. We harness the inherent characteristics of PDMS slabs; their ability to form conformal contact through van der Waals interactions in bringing the coated fluorescent layer on PDMS into close proximity of the photonic structure of interest. Fluorescence measurements are performed using the PDMS slab while in conformal contact with the test structure, allowing one to re-use these stamps for reliable evaluation over multiple samples. Transfer of the fluorescent film from the PDMS to the test structures is mitigated by the use of appropriate cross linkers that covalently bond the fluorescent film to the PDMS surface. To demonstrate the application potential of this approach, we report on the evaluation of fluorescence emission modulation from patterned nanoporous thin films, which are particularly challenging to evaluate using traditional approaches, and from plasmonic gratings supporting metal enhanced fluorescence. Comparison with traditional evaluation approaches has been made to showcase the superiority of the reported technique.