Research Group Si based Waveguide and Surface Plasmon Sensors Peter Debackere, Dirk Taillaert, Katrien De Vos, Stijn Scheerlinck, Peter Bienstman, Roel Baets Photonics Research Group INTEC – IMEC Ghent University

© intec Photonics Research Group - Vision Lab-on-Chip Miniaturize and integrate optical sensors

© intec Photonics Research Group - Lab on Chip Benefits Compactness allows high integration Massive parallelisation allows high throughput and multiparameter analysis. Low fabrication cost can lead to cost effective (even disposable) chips Biosensors : low fluid volume consumption Challenges Novel technology, not yet fully developed Scaling down detection principles Biosensors: Physical effects: e. g. capillary forces

© intec Photonics Research Group - Silicon-on-Insulator High Index Contrast 100  m 10  m 1  m Guide and confine light on extremely small scale Sensitivity increases with decreasing waveguide thickness and increasing index contrast Cavities: High Q factors, very small dimensions: Large Free Spectral Range (FSR)

© intec Photonics Research Group - Silicon-on-Insulator Deep UV lithography (248 nm) Standard Reactive Ion Etching Very high performance and reproducibility Easy integration with CMOS and/or microfluidics Wafer-scale processes Very high throughput Fabrication using standard CMOS processing steps

© intec Photonics Research Group - Silicon-on-Insulator Simulation : Price per Chip calculated for CMOS research fab wafer300 € mask(2)25000 € deep etch Litho1000 € /lot Etch1000 € /lot Strip1000 € /lot shallow etch Litho1000 € /lot Etch1000 € /lot Strip1000 € /lot dicing100 € /wafer number of chips/wafer (10 mm 2 )12500 number of wafers/lot chips0.402 €/chip

© intec Photonics Research Group - Silicon-on-Insulator High integration allowing multiparameter analysis High throughput fabrication, thus low fabrication cost High sensitivity for low fluid volumes Integration with microfluidics High reprocibility Lab-on-Chip Checklist

© intec Photonics Research Group - Active Research Community SOI Lab on a Chip Silicon Photonics Crystal Structures for Sensing PM Fauchet Mach-Zehnder sensing in SiN Lab-on-Chip Platform based on Highly Sensitive Nanophotonic Si Biosensors for Single Nucleotide DNA Testing J Sanchez del Rio Fast, Ultrasensitive Virus Detection using a Young Interferometer Sensor Aurel Ymeti Integrated Surface Plasmon Sensor Low-Index-Contrast SPR Sensor based on combined sensing of Modal, Phase and Amplitude Changes P Levy et al Long-range Surface Plasmon Sensor Long-range Surface Plasmon Waveguides and Devices in Lithium- Niobate P Berini

© intec Photonics Research Group - Focus Areas Label-free and multi-parameter detection of biomolecules Biosensors Refractive index sensing of appropriately functionalized surfaces DNA, mRNA, proteins, sugars, as well as enzymatic activities (proteases, kinase, DNAses) Waveguide sensors, Microring Cavities Surface Plasmon Sensors Strain sensor Measure strain in different in-plane directions, long term, immune from electromagnetic interference

© intec Photonics Research Group - Overview Introduction Biosensors Label-Free Biosensor: Ringresonator Theory Measurements: Bulk sensing Measurements: Surface sensing Label-Free Biosensor: Surface Plasmon Interferometer Theory Simulation: Intensity Measurement Mode Simulation: Wavelength Interrogation Mode Measurements Strain Sensor Conclusions

© intec Photonics Research Group - Biosensors Waveguide sensors :Microring Cavities Surface Plasmon Sensor Evanescent field sensing Technology and principle well understood Surface modification and biomolecule immobilisation are the biggest issues Sensing with surface plasmon modes Novel technology and principle Surface modification and biomolecule immobilisation well understood

© intec Photonics Research Group - Overview Introduction Biosensors Label-Free Biosensor: Ringresonator Theory Measurements: Bulk sensing Measurements: Surface sensing Label-Free Biosensor: Surface Plasmon Interferometer Theory Simulation: Intensity Measurement Mode Simulation: Wavelength Interrogation Mode Measurements Strain Sensor Conclusions

© intec Photonics Research Group - Theory Pass port Incoupling Port Drop Port biorecognition element (ligand) matching biomolecule (analyte) flow with biomolecules functional monolayer microring cavity biosensor

© intec Photonics Research Group - Theory Intensity Measurement Mode Monochromatic Input, monitor output power as a function of refractive index Advantage : real-time interaction registration Disadvantage : limited range Wavelength Interrogation Mode Broadband input, monitor resonance wavelength as a function of refractive index Advantage: easy to multiplex Disadvantage: slower detection method Sensitivity Increases with increasing Q factor of the ring

© intec Photonics Research Group - Measurement Setup Results presented here: Static measurements : zero flow rate Flow cell dimensions Ø~2mm 2 Towards microfluidic setup: Continuous flow with syringe pump Flow cell dimensions Ø~100μm 2 SiO 2 Light from tunable laser Light to photodetector Flow Cell Temperaturecontrol Si

© intec Photonics Research Group - Bulk refractive index sensing No surface chemistry involved Different salt concentrations Good repeatability (small variations around mean value) shift of 70nm/RIU ∆λmin= 5pm ∆n min =1*10 -5 RIU Sensitivity

© intec Photonics Research Group - Surface Chemistry 1. Cleaning and oxidation 2. Silanization: surfaces are dip-coated in APTES solution 3. Coupling of Biotin-LC-NHS

© intec Photonics Research Group - Surface Sensing Biotin/Avidin resonator buffer pH7,4 resonator avidin concentration biotin avidin biotin buffer pH7,4 resonator ∆λ∆λ ∆P∆P

© intec Photonics Research Group - Surface Sensing Biotin/Avidin High avidin concentrations: saturation Low avidin concentrations: quantitative measurements ∆λ min = 5pm  50ng/ml

© intec Photonics Research Group - Overview Introduction Label-Free Biosensor: Ringresonator Theory Measurements: Bulk sensing Measurements: Surface sensing Label-Free Biosensor: Surface Plasmon Interferometer Theory Simulation: Intensity Measurement Mode Simulation: Wavelength Interrogation Mode Measurements Strain Sensor Conclusions

© intec Photonics Research Group - Theory: Surface Plasmons Evanescent TM polarized electromagnetic waves bound to the surface of a metal Benefits for Biosensing High fields near the interface are very sensitive to refractive index changes Gold is very suitable for biochemistry From source To detector Prism Gold R

© intec Photonics Research Group - Theory Bulky surface plasmon biosensor Fully integrated lab-on-chip solution in Silicon-on-Insulator

© intec Photonics Research Group - Theory : Concept Si SiO 2 Sample medium 5 μm 4 μm 1 μm.22 μm 10 μm Surface Plasmon Interferometer Au

© intec Photonics Research Group - Simulation : Intensity Measurement Constructive Interference

© intec Photonics Research Group - Destructive Interference Simulation : Intensity Measurement

© intec Photonics Research Group - Optimalisation of Design Si thickness = 160 nm Length = 10  m Si thickness = 100 nm Length =  m Simulation : Intensity Measurement

© intec Photonics Research Group - Simulation : Intensity Measurement Sensitivity Analysis Change in the refractive index that causes a drop or rise in the transmission of 0.01 dB Sensitivity

© intec Photonics Research Group - Sensitivity Analysis Comparison Prism Coupled SPR 1 x 10-6 Grating Coupled SPR 5 x 10-5 MZI SOI Sensors 7 x 10-6 Integrated SPR LIC 5 x 10-6BUT Dimensions are two orders of magnitude smaller Simulation : Intensity Measurement

© intec Photonics Research Group - Shift of the spectral minimum Shift of the spectral minimum as a function of the bulk refractive index Simulation: Wavelength Interrogation

© intec Photonics Research Group - Sensitivity to adlayers 6 pm/nm For n=1.34 adlayer Simulation: Wavelength Interrogation

© intec Photonics Research Group - Measurement Setup Top View Side View

© intec Photonics Research Group - Measurement Results Compared to Theory Qualitative Agreement between experiment and theory Quantitative Need for a better fabrication process 5 μm Au O2 toplayer

© intec Photonics Research Group - Overview Introduction Label-Free Biosensor: Ringresonator Theory Measurements: Bulk sensing Measurements: Surface sensing Label-Free Biosensor: Surface Plasmon Interferometer Theory Sensitivity Fabrication Measurements Strain Sensor Conclusions

© intec Photonics Research Group - Strain sensor Introduction : Electrical resistance gage Most popular strain gage Moderate long term reliability No absolute measurements 2-D strain sensing Small resistance changes Fiber Bragg Gratings (FBG) More expensive Good long term reliability ‘Absolute measurements’ Only 1-D strain sensing EMI insensitive

© intec Photonics Research Group - Strain sensor Try to combine some advantages of electrical resistance gages and FBGs Strain  =  L/L typical  R = 0.2  ~  = 1000  typical  = 1000 pm ~  = 1000  SOI ring or racetrack resonator Resonance wavelength depends on strain Wavelength measurement = robust Wavelength demultiplexing (large FSR needed) electrical : resistance, optical : wavelength

© intec Photonics Research Group - Strain sensor Structure of SOI strain sensor Si SiO2 polyimide SiO2 10µm 2µm Layer stack Circuit layout

© intec Photonics Research Group - Strain sensor Thin foil strain sensor is bonded to Al plate for testing Bending test : bending the plate results in tensile strain at top surface Not yet fiber packaged Photo of measurement setup Sensor circuit

© intec Photonics Research Group - Strain sensor        Uni-axial strain  Experimental results : wavelength shift vs beam deflection, good agreement with theoretical predictions

© intec Photonics Research Group - Strain sensor Experimental results : Circular resonator :  =0.85  xx (pm/  ) Racetrack resonator  =0.99  xx,  =0.63  yy Sensitivity and cross-sensitivity can be improved by optimized design  =1.3  xx,  =0.3  yy (pm/  )

© intec Photonics Research Group - Overview Introduction Label-Free Biosensor: Ringresonator Theory Measurements: Bulk sensing Measurements: Surface sensing Label-Free Biosensor: Surface Plasmon Interferometer Theory Sensitivity Fabrication Measurements Strain Sensor Conclusions

© intec Photonics Research Group - Conclusions Theory & Design Proof of Principle Bulk Sensing Surface Chem Adlayer sensing OptimizeMulti para RIU We have demonstrated new type of optical strain sensor Thin foil SOI strain gage Sensitivity comparable to Fiber Bragg Gratings, but can measure strain in different in-plane directions P: 10ng/ml : 50ng/ml

© intec Photonics Research Group - Acknowledgements GOA Biosensor Project IAP Photon IWT Vlaanderen FWO Vlaanderen FOS&S

© intec Photonics Research Group -

Research Group Alternative (extended) Conclusions

© intec Photonics Research Group - Conclusions Silicon on Insulator Microring Cavities SOI microrings Extremely small high Q cavities Fabrication with standard CMOS processing techniques Characterization ∆n ~ 10-4 for bulk refractive index sensing LOD 10ng/ml avidin concentration

© intec Photonics Research Group - Conclusions Silicon-on-Insulator Surface Plasmon Sensors Theoretical Surface Plasmon Biosensor based on new concept Sensitivity comparable with current integrated SPR devices Design is very versatile Two orders of magnitude smaller than current integrated SPR devices Experimental Proof-of-Principle Discrepancy between theoretical predictions and experimental values

© intec Photonics Research Group - Conclusions Silicon-on-Insulator Strain Sensors We have demonstrated new type of optical strain sensor Thin foil SOI strain gage Sensitivity comparable to Fiber Bragg Gratings, but can measure strain in different in-plane directions

Research Group APPENDIX

© intec Photonics Research Group - Si SiO 2 H2OH2OSample medium Simulation: Wavelength Interrogation

© intec Photonics Research Group - Novel Concept Coupling to SP modes

© intec Photonics Research Group - Novel Concept Mode dispersion gold-clad waveguide Waveguide mode cutoff

© intec Photonics Research Group - SPR History Integrated Surface Plasmon Resonance DevicePrinciple Thin metallic layers Symmetric cladding Supermodes Asymmetric cladding Interface Modes H2OH2O Sample medium Schematical Device Setup H2OH2O Sample medium Drawbacks Quite large (mm scale)Quite large (mm scale) Not suited for high level integration Not suited for high level integration Design limited to low-index contrast due to phase matching considerationsDesign limited to low-index contrast due to phase matching considerations

© intec Photonics Research Group - Intensity Measurement/ SimulationParameters Length of the sensing region Length of the sensing region Thickness of the Si waveguide Thickness of the Si waveguide Thickness of the Au layer Thickness of the Au layer Limitations Position of the minima : Dip in the transmission micron should be near n = 1.33 Position of the minima : Dip in the transmission micron should be near n = 1.33 Maximum Visibility : Loss along both ‘arms’ has to be equal Maximum Visibility : Loss along both ‘arms’ has to be equal

© intec Photonics Research Group - Sensitivity Analysis Sensitivity to adlayers 6 pm/nm For n=1.34 adlayer

© intec Photonics Research Group -