Optical Antennas for Raman Spectroscopy

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Optical Antennas for Raman Spectroscopy

• Laura Matloff
• Mentor Matteo Staffaroni (EECS)
• Faculty Sponsor Prof. Yablonovitch

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At Airports
Compact desktop explosives/narcotics detection
system
Security Guy
Sample collection swab
Your check-in luggage
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(No Transcript)
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nose
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Raman Spectroscopy
Pump Photon
Virtual Level
Pump Photon
Excited State
Ground State
Target Molecule in Ground State
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Raman Spectroscopy
Pump Photon
Virtual Level
Stokes-shifted Photon
Stokes-shifted Photon
Pump Photon
Excited State
Ground State
Target Molecule in Excited State
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The likelihood of a Raman scattering event
depends on the intensity of the light in the
neighborhood of the molecule
Pump Photons
Photon Counts
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514
524
524
534
544
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Wavelength (nm)
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For single molecule detection (E-Field
enhancement)4 gt 1014
Pump Photons
Photon Counts
Stokes-shifted Photons
554
514
524
524
534
544
504
Wavelength (nm)
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The Dipole Antenna
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Antenna Arm Length (µm)
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Single molecule detection requires electric field
enhancement of 1014
1016 1014 1012 1010 108 106 104 102 1
Optical Antenna
Antenna Arm Length (µm)
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Single molecule detection requires electric field
enhancement of 1014
1016 1014 1012 1010 108 106 104 102 1
Optical Antenna
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Single molecule detection requires electric field
enhancement of 1014
1016 1014 1012 1010 108 106 104 102 1
Optical Antenna
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Single molecule detection requires electric field
enhancement of 1014
1016 1014 1012 1010 108 106 104 102 1
Optical Antenna
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Single molecule detection requires electric field
enhancement of 1014
1016 1014 1012 1010 108 106 104 102 1
Grating Coupler
Optical Antenna
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Grating Coupler
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COMSOL Model
Without Grating
With Grating
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Transformer
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-

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3D Taper (Optical Transformer)
Au
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Single molecule detection requires electric field
enhancement of 1014
1016 1014 1012 1010 108 106 104 102 1
Optical Transformer
Grating Coupler
Optical Antenna
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2D Taper
Au
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The Side View
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The Side View
Au
Initial Thickness
Taper Angle
Final Thickness
Au
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Optimizing Taper Angle
Power Throughput ()
Taper Angle (Degrees)
Where Initial Thickness 50nm and Final
Thickness 5nm
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Transformer Action in 2D
Vout / Vin
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Final Plate Spacing (nm)
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Transformer Action in 2D
Vout / Vin
10
1
Final Plate Spacing (nm)
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E-Field Enhancement in 2D
Eout / Ein
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Transformer Action in 3D
Vout / Vin
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E-Field Enhancement in 3D
Eout / Ein
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Single molecule detection requires electric field
enhancement of 1014
1016 1014 1012 1010 108 106 104 102 1
Optical Transformer
Grating Coupler
Optical Antenna
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Citations

• Pictures
• http//unitedlp.com/images/power_Lines.jpg
• www.jamd.com/image/g/1714820
• http//www.macsparky.com/wp-content/uploads/2008/0
  1/crowd.jpg