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

Abstract

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.

Optofluidic Sensor for Inline Hemolysis Detection on Whole Blood

“…The plasma separation is achieved with an integrated nanofilter comprising an array of nanowells. So far, waveguide absorption spectroscopy has been demonstrated for sensing pH value, protein, − and molecules. − Separation of blood plasma and RBCs is achieved by either active methods, such as magnetic, , dielectrophoretic, , and acoustic, , or passive methods, such as hydrodynamic, − sedimentation, , and filtration. − Our optofluidic strategy is based on an innovative dual function of nanofilters that act as a component of the waveguide as well as a functional filter for RBCs. The nanofilters enable light propagation without diffraction and scattering while effectively blocking cells or platelets with short diffusion length and time, as shown schematically in Figure a.…”