Revealing plasmonic-photonic interaction via single-particle microresonator spectroscopy and tailoring weak-to-strong coupling
1. 1
Feng Pan
Department of Chemistry
University of Wisconsin Madison
Group: https://goldsmith.chem.wisc.edu/
Revealing Plasmonic-Photonic Interaction
via Single-Particle Microresonator Spectroscopy
and Tailoring Weak-To-Strong Coupling
Email: fpan22@wisc.edu
APS March Meeting 2020
March 2-6 Denver, CO
2. 2
Localized surface plasmon (LSP)
= electron cloud
Au nanorod (AuNR)
Longitudinal dipolar mode
wikipedia
Plasmonic-Photonic Cavity
Low Q factor (~10)
Ultrasmall mode volume (10^-6 λ3)
Electron cloud oscillation
Photonic cavity
Lončar, M. Appl. Phys. Lett. 2009, 94, 121106.
Heylman, K.D. et al. Adv. Mater. 2017, 29, 1700037
High Q factor (up to 108)
Tunable mode volume (down to λ3)
3. 3Baaske et al Nat. Photon., 2016, 10, 733
Why Plasmonic-Photonic Cavity?
Label-free sensing
Low Q factor (~10)
Ultrasmall mode volume (10-6 λ3)
High Q factor (up to 108)
Tunable mode volume (down to λ3)
Plasmonic cavity
Photonic cavity
Can plasmonic-photonic cavity inherit some characteristics?
Hybrids win!!!
Strong light-matter interaction
Applications
Cavity quantum electrodynamics
Single photon sources
Enhanced Raman spectroscopy
…
Higher Purcell factor?
Koenderink, A.F. et al. Nanophotonics 2019, 8, 1513
12. Contribution from individual system parameters
• LSP nonradiative dissipation is dominant regardless of observables
• WGM-character dissipations gain more weight in transmission
12
Pan F.*, Smith K.C.*, et al. Nano Lett. 2020, 20, 50 (Cover article)
13. 13
Tailoring weak-to-strong coupling
(ℏg∼10−4 eV, ℏγ0,Tot∼10−2 eV, ℏγ1,Tot∼10−6 eV)
Ω ∝ 𝑔 ∗ 𝑁
• Multiple LSPs interact with a common
WGM
• LSP-WGM coupling: mode overlapping
Dicke effect
Armani A. et al. Opt. Lett. 2010, 35, 459
Polymer
matrix
14. 14
0 µm
0.2 µm
0.4 µm
0.8 µm
1.0 µm
1.5 µm
2.0 µm
3.0 µm
Li, B. et al. APL, 2010, 96, 251109
Simulation
• Coating thickness is
controllable, i.e. g is
tunable
• g can be scaled by up
to 50 times
according to
numerical simulation
PDMS (index-matching material)
Drawing out WGM electromagnetic (EM) field
Coating microresonators with PDMS Advantages
IncreasingPDMSthickness
EM field maximizes at the interface
16. 16
Acknowledgements
Collaborators:
Kevin Smith, Niket Thakkar,
David Masiello (UWashington)
Prof. Randall Goldsmith
Goldsmith Group Members:
Dr. Hoang Nguyen
Dr. Kassandra Knapper
Dr. Kevin Heylmen
Dr. Erik Horak
Morgan Rea
NSF-CHE
NSF-DMR
NSF-IDBR
Editor's Notes
Cannot be achieved by microcavities alone.
In our technique, we’re doing absorption on a toroidal microresonator, which is made of a silica disc and silicon pillar. This type of resonator has a very quality factor which allows light to propagate within it millions of times. Along with small mode volume, this device is very powerful for label-free detection and SM measurements. How do we measure absorption? Specifically, when a tapered optical fiber is brought very close to the resonator, light of wavelength meeting the resonant condition will be coupled into the resonator. If we measure the transmission of light through the fiber, a transmission dip will show up. When there is an object sitting on the toroid and being excited by a free-space pump beam, the excited species will dissipate the heat to local environment, i.e. the resonator, changing the refractive index and shifting the resonance. Using the res shift as a probe, we can calculate how much heat is being dissipated and then divide it by the power density, which is the abs cross section.
Shape of the fano seems to depend on the part of the spectrum we examine. So we see peaks go up and down. We also only see these weird lineshapes, called fano resonance, when the object is on the outer rim of our toroid, where the WGM and the object can interact most strongly.