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Evanescent field Sensors Based on Tantalum Pentoxide Waveguides – A Review

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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.

No MeSH data available.


Optical arrangement for reflected-mode operation of integrated optical grating coupler. From [41], Copyright Elsevier (1996).
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f7-sensors-08-00711: Optical arrangement for reflected-mode operation of integrated optical grating coupler. From [41], Copyright Elsevier (1996).

Mentions: To overcome such limitations, Brandenburg et al. developed an integrated optical grating coupler in reflected-mode operation having the advantage that no critical alignments for coupling light into the waveguide were necessary and that any moving parts could be avoided. The system, at first implemented using TiO2- and SiO2- waveguides, was applicable in humidity sensing with a resolution of Δneff, min = 1 x 10-5 [40]. In 1996, Brandenburg et al. reached a resolution of about Δneff, min = 3 x 10-6 in reflected-mode operation with an integrated optical grating coupler based on Ta2O5-waveguides. They calculated a detection limit of 0.2 μg/mL or 1.4 x 10-9 M for human IgG using protein G as capture molecule [41]. The set-up is shown in Figure 7. A laser beam is focused by a lens onto an embedded grating in a Ta2O5-waveguide layer, thereby creating a continuum of coupling angles. The optical device is arranged in order to cover all coupling angles in the range of 0.7° expected during the measurement. Only the light obeying the coupling condition (eq. 16) is coupled into the waveguide, such that in the reflected beam a dark line corresponding to the coupling angle at the measured effective refractive index can be observed. On a CCD array the reflected light is detected and in the resulting intensity distribution the minimum position is determined.


Evanescent field Sensors Based on Tantalum Pentoxide Waveguides – A Review
Optical arrangement for reflected-mode operation of integrated optical grating coupler. From [41], Copyright Elsevier (1996).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3927514&req=5

f7-sensors-08-00711: Optical arrangement for reflected-mode operation of integrated optical grating coupler. From [41], Copyright Elsevier (1996).
Mentions: To overcome such limitations, Brandenburg et al. developed an integrated optical grating coupler in reflected-mode operation having the advantage that no critical alignments for coupling light into the waveguide were necessary and that any moving parts could be avoided. The system, at first implemented using TiO2- and SiO2- waveguides, was applicable in humidity sensing with a resolution of Δneff, min = 1 x 10-5 [40]. In 1996, Brandenburg et al. reached a resolution of about Δneff, min = 3 x 10-6 in reflected-mode operation with an integrated optical grating coupler based on Ta2O5-waveguides. They calculated a detection limit of 0.2 μg/mL or 1.4 x 10-9 M for human IgG using protein G as capture molecule [41]. The set-up is shown in Figure 7. A laser beam is focused by a lens onto an embedded grating in a Ta2O5-waveguide layer, thereby creating a continuum of coupling angles. The optical device is arranged in order to cover all coupling angles in the range of 0.7° expected during the measurement. Only the light obeying the coupling condition (eq. 16) is coupled into the waveguide, such that in the reflected beam a dark line corresponding to the coupling angle at the measured effective refractive index can be observed. On a CCD array the reflected light is detected and in the resulting intensity distribution the minimum position is determined.

View Article: PubMed Central - PubMed

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.

No MeSH data available.