Evanescent field Sensors Based on Tantalum Pentoxide Waveguides – A Review

Abstract

Evanescent field sensors based on waveguide surfaces play an important role where high sensitivity is required. Particularly tantalum pentoxide (Ta2O5) is a suitable material for thin-film waveguides due to its high refractive index and low attenuation. Many label-free biosensor systems such as grating couplers and interferometric sensors as well as fluorescence-based systems benefit from this waveguide material leading to extremely high sensitivity. Some biosensor systems based on Ta2O5 waveguides already took the step into commercialization. This report reviews the various detection systems in terms of limit of detection, the applications, and the suitable surface chemistry.

Embossable grating couplers for planar evanescent wave sensors

“…Therefore, the struc− tures with grating couplers of the high groove density c are frequently preferred. The obtained detection limits involv− ing the change of effective refractive index (DN) min and the refractive index of the cover (Dn c ) min are comparable with the parameters of the commercially available instrument [18], as well as with the parameters of similar structures pre− sented by other authors [1,[35][36][37][38]. In Ref.…”

“…In Ref. 38, an overview on different types of grating coupler sensors and their de− tection limits is presented.…”

Fem-Based Method for the Simulation of Dielectric Waveguide Grating Biosensors

“…For a Ta 2 O 5 chip, the described k-values are varying between < 10 −4 [20] and 0.02 [1]. As explained in [20], there are also losses at the substrate-film and the film-cover interface.…”

“…Different configurations for label-free waveguide based sensor are possible [1][2][3]. The dielectric waveguide with input/output grating coupler is one of the simplest and cheaper solutions.…”

Broadband plasmonic couplers for light trapping and waveguiding

“…Tantalum pentoxide (Ta 2 O 5 ) was originally used in anti-reflection coatings for solar cells, and later it was introduced in waveguiding application. Due to its characteristics: low absorption, high refractive index, chemical and thermal stability [5]; this material is now widely used as optical waveguide [6].…”