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Experimental Validation of the Sensitivity of Waveguide Grating Based Refractometric (Bio)sensors.

Gartmann TE, Kehl F - Biosensors (Basel) (2015)

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: CSEM Centre Suisse d'Electronique et de Microtechnique SA, Bahnhofstrasse 1, Landquart CH-7302, Switzerland. thomas.gartmann@csem.ch.

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.

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Schematic drawing of the investigated waveguide grating chips. (a) Cross section (not to scale); (b) Top view: Chip with 24 gratings with waveguide thickness hf1 and hf2, respectively, whereas the central eight gratings (four of each height) have been considered per measurement per chip.
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biosensors-05-00187-f002: Schematic drawing of the investigated waveguide grating chips. (a) Cross section (not to scale); (b) Top view: Chip with 24 gratings with waveguide thickness hf1 and hf2, respectively, whereas the central eight gratings (four of each height) have been considered per measurement per chip.

Mentions: The waveguide of the investigated sensor consists of a Ta2O5 film on a structured glass substrate (D263T by Schott, Mainz, Germany), as schematically depicted in Figure 2. To facilitate coupling via the substrate, a broadband anti-reflective coating was deposited on its reverse side. In a second production step, a rectangular grating (0.9 mm by 0.9 mm) was structured into the glass substrate using interference photolithography and reactive ion etching (RIE) in a CHF3/Ar plasma (Figure 3). The developed photoresist was removed by O2 plasma stripping and subsequently, a first layer of Ta2O5 was magnetron sputtered onto the substrate, followed by the deposition of a sacrificial photoresist layer in the regions where a thinner waveguide thickness was desired. A second layer of Ta2O5 was sputtered onto the sample thereafter and the production was completed with a lift-off process to uncover the thinner waveguide regions. Average waveguide thicknesses hf ranging from 83.0 nm ± 0.6 nm to 329.63 nm ± 0.08 nm with a root mean square (RMS) surface roughness of approximately 1.2 nm were produced. The waveguide thicknesses were measured using a spectrometer (Lambda 800, PerkinElmer, Waltham, MA, USA), as well as with a prism coupler (Model 2010, METRICON, Pennington, NJ, USA). The rectangular gratings were produced with a grating depth hg of 12 ± 2 nm and a grating period Λ of 360 ± 0.1 nm.


Experimental Validation of the Sensitivity of Waveguide Grating Based Refractometric (Bio)sensors.

Gartmann TE, Kehl F - Biosensors (Basel) (2015)

Schematic drawing of the investigated waveguide grating chips. (a) Cross section (not to scale); (b) Top view: Chip with 24 gratings with waveguide thickness hf1 and hf2, respectively, whereas the central eight gratings (four of each height) have been considered per measurement per chip.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493545&req=5

biosensors-05-00187-f002: Schematic drawing of the investigated waveguide grating chips. (a) Cross section (not to scale); (b) Top view: Chip with 24 gratings with waveguide thickness hf1 and hf2, respectively, whereas the central eight gratings (four of each height) have been considered per measurement per chip.
Mentions: The waveguide of the investigated sensor consists of a Ta2O5 film on a structured glass substrate (D263T by Schott, Mainz, Germany), as schematically depicted in Figure 2. To facilitate coupling via the substrate, a broadband anti-reflective coating was deposited on its reverse side. In a second production step, a rectangular grating (0.9 mm by 0.9 mm) was structured into the glass substrate using interference photolithography and reactive ion etching (RIE) in a CHF3/Ar plasma (Figure 3). The developed photoresist was removed by O2 plasma stripping and subsequently, a first layer of Ta2O5 was magnetron sputtered onto the substrate, followed by the deposition of a sacrificial photoresist layer in the regions where a thinner waveguide thickness was desired. A second layer of Ta2O5 was sputtered onto the sample thereafter and the production was completed with a lift-off process to uncover the thinner waveguide regions. Average waveguide thicknesses hf ranging from 83.0 nm ± 0.6 nm to 329.63 nm ± 0.08 nm with a root mean square (RMS) surface roughness of approximately 1.2 nm were produced. The waveguide thicknesses were measured using a spectrometer (Lambda 800, PerkinElmer, Waltham, MA, USA), as well as with a prism coupler (Model 2010, METRICON, Pennington, NJ, USA). The rectangular gratings were produced with a grating depth hg of 12 ± 2 nm and a grating period Λ of 360 ± 0.1 nm.

Bottom Line: 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.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.

View Article: PubMed Central - PubMed

Affiliation: CSEM Centre Suisse d'Electronique et de Microtechnique SA, Bahnhofstrasse 1, Landquart CH-7302, Switzerland. thomas.gartmann@csem.ch.

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.

Show MeSH
Related in: MedlinePlus