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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.


(a) Cut through dual period sensor chip. (b) Cut through thickness-modulated sensor chip. From [46], Copyright Elsevier (2003).
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f9-sensors-08-00711: (a) Cut through dual period sensor chip. (b) Cut through thickness-modulated sensor chip. From [46], Copyright Elsevier (2003).

Mentions: The basic principle of the WIOS is to scan for the resonance peak of a grating coupler. A monomode waveguide is structured with two corrugated grating regions, one providing the incoupling region for the incident beam, the other for outcoupling, respectively. While the latter exhibits a thickness of 300 nm, the incoupling region is 150 nm thick, both structured by dry etching. After excitation of a guided wave and penetration into adjacent layers of the multilayer-waveguide, the optical properties change and affect the phase shift upon Fresnel reflection. According to this, the change of the effective refractive index can be observed by monitoring the resonance peak of the incoupling grating. For different sensing applications the WIOS enables two configurations: one exhibits a grating with different periods for in- and output pad, the other a uniform grating with different film heights (Figure 9).


Evanescent field Sensors Based on Tantalum Pentoxide Waveguides – A Review
(a) Cut through dual period sensor chip. (b) Cut through thickness-modulated sensor chip. From [46], Copyright Elsevier (2003).
© Copyright Policy
Related In: Results  -  Collection

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

f9-sensors-08-00711: (a) Cut through dual period sensor chip. (b) Cut through thickness-modulated sensor chip. From [46], Copyright Elsevier (2003).
Mentions: The basic principle of the WIOS is to scan for the resonance peak of a grating coupler. A monomode waveguide is structured with two corrugated grating regions, one providing the incoupling region for the incident beam, the other for outcoupling, respectively. While the latter exhibits a thickness of 300 nm, the incoupling region is 150 nm thick, both structured by dry etching. After excitation of a guided wave and penetration into adjacent layers of the multilayer-waveguide, the optical properties change and affect the phase shift upon Fresnel reflection. According to this, the change of the effective refractive index can be observed by monitoring the resonance peak of the incoupling grating. For different sensing applications the WIOS enables two configurations: one exhibits a grating with different periods for in- and output pad, the other a uniform grating with different film heights (Figure 9).

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.