Abstract
Despite the fact that the theoretical foundations of the sensitivity of waveguide grating based (bio)sensors are well-known, understood and their implications anticipated by the scientific community since several decades, to our knowledge, no prior publication has experimentally confirmed waveguide sensitivity for multiple film thicknesses, wavelengths and polarization of the propagating light. In this paper, the bulk refractive index sensitivity versus waveguide thickness of said refractometric sensors is experimentally determined and compared with predictions based on established theory. The effective refractive indices and the corresponding sensitivity were determined via the sensors’ coupling angles at different cover refractive indices for transverse electric as well as transverse magnetic polarized illumination at various wavelengths in the visible and near-infrared. The theoretical sensitivity was calculated by solving the mode equation for a three layer waveguide.
Highlights
Waveguide grating based sensors are highly sensitive optical transducers, mainly applied for bulk refractometric or label-freesensing, to accurately determine the refractive index of a fluid or to detect the interaction, presence and concentration ofmolecules [1]
Both measured and calculated sensitivities for the investigated waveguide grating basedsensor are displayed in Figure 7 for all measured waveguide thicknesses, wavelengths and polarizations of the incident light
The root-mean-square deviation (RMSD) was 0.006 ± 0.003, which is equal to the average standard deviation of the measured sensitivities
Summary
Waveguide grating based sensors are highly sensitive optical transducers, mainly applied for bulk refractometric or label-free (bio)sensing, to accurately determine the refractive index of a fluid or to detect the interaction, presence and concentration of (bio)molecules [1]. A key parameter of such a sensor is its sensitivity It is important for the development of a new sensor to choose its overall design and the individual design parameters for a maximized sensitivity. The aim of this publication is neither to theoretically assess the sensitivity of said sensors nor to maximize it, but to provide experimentally measured data to verify well-established theory regarding the sensitivity of dielectric waveguide grating based (bio)chemical and refractometric sensors. These results have been anticipated for several decades but lack of a systematic experimental verification
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