Extension of the broadband single-mode integrated optical waveguide technique to the ultraviolet spectral region and its applications

• Published in: Analyst (London) 2014-03, Vol.139 (6), p.1396-142
• Main Authors: Wiederkehr, Rodrigo S, Mendes, Sergio B
• Format: Article
• Language: English
• Subjects: Adsorption; Aluminum Oxide - chemistry; Bacterial Proteins - chemistry; Bacteriochlorophyll A - chemistry; Broadband; Equipment Design; Optical waveguides; Rhodobacter sphaeroides - chemistry; Silicon Dioxide - chemistry; Solvation; Spectra; Spectrophotometry, Ultraviolet - instrumentation; Surface chemistry; Ultraviolet; Wavelengths
• ISSN: 0003-2654; 1364-5528
• DOI: 10.1039/c3an02201c

We report here the fabrication, characterization, and application of a single-mode integrated optical waveguide (IOW) spectrometer capable of acquiring optical absorbance spectra of surface-immobilized molecules in the visible and ultraviolet spectral region down to 315 nm. The UV-extension of the single-mode IOW technique to shorter wavelengths was made possible by our development of a low-loss single-mode dielectric waveguide in the UV region based on an alumina film grown by atomic layer deposition (ALD) over a high quality fused silica substrate, and by our design/fabrication of a broadband waveguide coupler formed by an integrated diffraction grating combined with a highly anamorphic optical beam of large numerical aperture. As an application of the developed technology, we report here the surface adsorption process of bacteriochlorophyll a on different interfaces using its Soret absorption band centred at 370 nm. The effects of different chemical compositions at the solid-liquid interface on the adsorption and spectral properties of bacteriochlorophyll a were determined from the polarized UV-Vis IOW spectra acquired with the developed instrumentation. The spectral extension of the single-mode IOW technique into the ultraviolet region is an important advance as it enables extremely sensitive studies in key characteristics of surface molecular processes ( e.g. , protein unfolding and solvation of aromatic amino-acid groups under surface binding) whose spectral features are mainly located at wavelengths below the visible spectrum. We report here the fabrication, characterization, and application of a single-mode integrated optical waveguide (IOW) spectrometer capable of acquiring optical absorbance spectra of surface-immobilized molecules in the visible and ultraviolet spectral region down to 315 nm.