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Si based Waveguide and Surface Plasmon Sensors

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. Vision. Lab-on-Chip. Miniaturize and integrate optical sensors. Lab on Chip. Benefits

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Si based Waveguide and Surface Plasmon Sensors

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  1. 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

  2. Vision Lab-on-Chip Miniaturize and integrate optical sensors

  3. 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

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

  5. 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

  6. Silicon-on-Insulator • Simulation : Price per Chip calculated for CMOS research fab • wafer 300 € • mask(2) 25000 € • deep etch • Litho 1000 € /lot • Etch 1000 € /lot • Strip 1000 € /lot • shallow etch • Litho 1000 € /lot • Etch 1000 € /lot • Strip 1000 € /lot • dicing 100 € /wafer • number of chips/wafer (10 mm2) 12500 • number of wafers/lot 23 • 100.000 chips 0.402 €/chip

  7. Silicon-on-Insulator Lab-on-Chip Checklist

  8. Active Research Community • SOI Lab on a ChipSilicon 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

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

  10. 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

  11. Biosensors • Waveguide sensors :Microring Cavities • Evanescent field sensing • Technology and principle well understood • Surface modification and biomolecule immobilisation are the biggest issues Surface Plasmon Sensor • Sensing with surface plasmon modes • Novel technology and principle • Surface modification and biomolecule immobilisation well understood

  12. 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

  13. flow with biomolecules matching biomolecule (analyte) biorecognition element (ligand) functional monolayer microring cavity biosensor Theory Incoupling Port Drop Port Pass port

  14. 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

  15. Measurement Setup Light from tunable laser Light to photodetector Flow Cell SiO2 Si Temperaturecontrol Results presented here: Static measurements : zero flow rate Flow cell dimensions Ø~2mm2 Towards microfluidic setup: Continuous flowwith syringe pumpFlow cell dimensionsØ~100μm2

  16. Bulk refractive index sensing • No surface chemistry involved • Different salt concentrations • Good repeatability (small variations around mean value) Sensitivity • shift of 70nm/RIU • ∆λmin= 5pm • ∆nmin=1*10-5RIU

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

  18. buffer pH7,4 buffer pH7,4 avidin concentration avidin biotin biotin resonator resonator resonator Surface Sensing Biotin/Avidin ∆P ∆λ

  19. Surface Sensing Biotin/Avidin • High avidin concentrations: saturation • Low avidin concentrations: quantitative measurements • ∆λmin= 5pm 50ng/ml

  20. 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

  21. R  From source To detector Prism Gold 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

  22. Theory Fully integrated lab-on-chip solution in Silicon-on-Insulator Bulky surface plasmon biosensor

  23. Theory : Concept 5 μm Sample medium .22μm Si 1 μm SiO2 4 μm Si 10 μm Surface Plasmon Interferometer Au

  24. Constructive Interference Simulation : Intensity Measurement

  25. Destructive Interference Simulation : Intensity Measurement

  26. Optimalisation of Design Si thickness = 160 nm Length = 10 m Si thickness = 100 nm Length = 6.055 m Simulation : Intensity Measurement

  27. Sensitivity Analysis Sensitivity 10-5 Change in the refractive index that causes a drop or rise in the transmission of 0.01 dB 10-6 10-7 Simulation : Intensity Measurement

  28. 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 10-6 10-5 BUT Dimensions are two orders of magnitude smaller 10-6 10-7 Simulation : Intensity Measurement

  29. Shift of the spectral minimum Shift of the spectral minimum as a function of the bulk refractive index Simulation: Wavelength Interrogation

  30. Sensitivity to adlayers Simulation: Wavelength Interrogation For n=1.34 adlayer 6 pm/nm

  31. Side View Top View Measurement Setup

  32. Measurement Results • Compared to Theory • Qualitative Agreement between experiment and theory • Quantitative Need for a better fabrication process 5 μm Au O2 toplayer

  33. 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

  34. 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 Strain sensor

  35. Strain sensor • Try to combine some advantages of electrical resistance gages and FBGs • Strain e = DL/L • typical DR = 0.2 W~ e = 1000me • typical Dl = 1000 pm ~e = 1000me • SOI ring or racetrack resonator • Resonance wavelength depends on strain • Wavelength measurement = robust • Wavelength demultiplexing(large FSR needed) electrical : resistance, optical : wavelength

  36. Strain sensor • Structure of SOI strain sensor Layer stack Circuit layout SiO2 2µm Si SiO2 10µm polyimide

  37. 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

  38. Strain sensor Experimental results : wavelength shift vs beam deflection, good agreement with theoretical predictions Dl2 Dl1 Dl3 l1 l2 Dl4 l3 l4 Uni-axial strain

  39. Strain sensor • Experimental results : • Circular resonator : Dl=0.85exx (pm/me) • Racetrack resonator : Dl=0.99exx , Dl=0.63eyy • Sensitivity and cross-sensitivity can be improved by optimized design • Dl=1.3exx , Dl=0.3eyy (pm/me)

  40. 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

  41. Conclusions Theory & Design Proof of Principle Bulk Sensing Surface Chem Adlayer sensing Optimize Multi para P: 10ng/ml: 50ng/ml 10-5 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

  42. Acknowledgements • GOA Biosensor Project • IAP Photon • IWT Vlaanderen • FWO Vlaanderen • FOS&S

  43. Alternative (extended) Conclusions

  44. 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

  45. 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

  46. 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

  47. APPENDIX

  48. Sample medium H2O 5 Si 0.220 SiO2 1 Si 4 10 Simulation: Wavelength Interrogation

  49. Coupling to SP modes Novel Concept

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