What is plasmonics?

ADOPT Winter School 2014
Merging silicon photonics and
plasmonics
Prof. Min Qiu
Optics and Photonics, Royal Institute of Technology, Sweden
and Optical Engineering, Zhejiang University, China
Contents
 Introduction to plasmonics
 Plasmonic waveguides
 Hybrid integration of plasmonic
waveguides and silicon wire waveguides
 Optical wireless interconnect network
based on plasmonic antennas
 Plasmonic light absorber
 Conclusions
Nanophotonics
What is plasmonics?
The science of plasmonics is dealing with
generation, manipulation, and detection of
surface plasmon polaritons (SPPs).
SPP: Quasi-particle due to coupling of light and
surface plasmon (SP).
SP: electron oscillation wave at metal surfaces.
Nanophotonics
Waveguiding with one interface
Metal has a negative e.
Nanophotonics
Field pattern of a SPP
 = p/2
kx
vacuum
metal
2D field distribution in xz plane. The colormap
denotes Hy field, while the arrows indicate the
E field (consisting both Ex and Ez).
Nanophotonics
Contents
 Introduction to plasmonics
 Plasmonic waveguides
 Hybrid integration of plasmonic
waveguides and silicon wire waveguides
 Optical wireless interconnect network
based on plasmonic antennas
 Plasmonic light absorber
 Conclusions
Nanophotonics
SPP waveguides
Various plasmonic waveguides with lateral confinement.
(a) Strip SPP waveguide; (b) Suspended strip waveguide; (c) Slot
waveguide; (d) V-channel waveguide; (e) -wedge waveguide; (f)
metallic fiber waveguide. Line-shaded regions are metal; greyshaded regions are dielectric materials.
Nanophotonics
Channel plasmon subwavelength waveguide
components
V-channel Plasmon polariton guide
Propagation length is only a few tens of micrometers
Bozhevolnyi, S.I., et.al., Nature, 440,508,2006
M. Yan and M. Qiu, J. Opt. Soc. Am. B 24, p. 2333 (2007)
Nanophotonics
Plasmonic gap waveguides
λ=1.55μm
εAu=-115-11.2i
Subwavelength confinement!
Loss is a big issue!
Nanophotonics
Nanophotonics
KTH 11
Plasmonic waveguides:
Experiments
Diameter: 300 nm
Length: 45 μm.
Logarithm of intensity (a.u)

Leaky modes!
Propagation loss
1550 nm
980 nm












Distance between exictation spot and wire end (m)
980 nm: 0.41 dB/µ m (L0=10.5 µ m)
1550 nm: 0.3 dB/µ m (L0=14.5 µ m)
Collaboration with LM Tong
Qiang Li et al, IEEE JSTQE, 17, 1107, 2011
Nanophotonics 12
Contents
 Introduction to plasmonics
 Plasmonic waveguides
 Hybrid integration of plasmonic
waveguides and silicon wire waveguides
 Optical wireless interconnect network
based on plasmonic antennas
 Plasmonic light absorber
 Conclusions
Nanophotonics
Hybrid integration
Dielectric waveguides
 Long
 Large bending radius
 Large mode area
Plasmonic waveguides
 Short
 Small bending radius
 High confinement
 Low loss
 Easy in-coupling
 ...
 High loss
 Difficult in-coupling
 ...
Miniturization
Hybrid integration of plasmonics and dieletrics
Only using plasmonics when it needed!
Nanophotonics 14
Broadband high-efficiency
Plasmonic–Silicon waveguide coupler
Average coupling efficiency is about
4.5 dB (35%).
Au
Si
SiO2
Au
250nm Au
Air
Au
SiO2
J. Tian et al, “Broadband high-efficiency surface-plasmon-polariton coupler with siliconmetal interface”, Appl. Phys. Lett. 95, 013504 (2009)
Nanophotonics 15
Broadband coupler
Average coupling efficiency is about
4.5 dB (35%).
Appl. Phys. Lett. 95, 013504 (2009)
The average loss is about −2.5 dB/m
(Simulation results −1.5 dB/m)
Nanophotonics 16
Plasmonic-dielectric coupler
450nm
With a 0.4μm-long HP
taper, η=70%.
HP-taper coupler
Y. Song et al, Opt. Express. 18, 13173, 2010
Nanophotonics 17
Coupling of Plasmonic and Photonic
Nanowires for Hybrid Nanophotonic Circuits
Prof. Limin Tong’s group in Zhejiang U, China
Q factor 520!
X. Guo, M. Qiu, et al, “Direct Coupling of Plasmonic and Photonic Nanowires for Hybrid
Nanophotonic Components and Circuits”, Nano Lett. 9 (12), pp 4515–4519 (2009)
Nanophotonics
Nanophotonics
KTH 18
Hybrid coupler composed of metal-insulator-metal
plasmonic waveguide and silicon dielectric waveguide
Output
power from the two output arms
quasi-even
Metal-insulator-metal
plasmonic waveguide
quasi-odd
Coupling insensitive to
slot structural parameters
Si dielectric
waveguide
hybrid directional coupler
W1=260 nm, H1=220 nm
W2=150 nm, H2=200 nm
S=250 nm
• Insertion loss 1.4 dB
• Propagation loss 0.18 dB/m
• Extinction ration 16 dB
• Coupling length 4.5 m
Q. Li et al, Opt. Express. 18, 15531, 2010
Nanophotonics 19
Hybrid coupler composed of cap plasmonic waveguide
and silicon dielectric waveguide
Metal cap plasmonic waveguide
Si dielectric
waveguide
plasmonic mode dielectric mode
quasi-even mode quasi-odd mode
Ey profiles of TM mode
Q. Li, et al Opt. Lett. 35, 3153, 2010
d=250 nm:
• Insertion loss 0.2 dB (including the
propagation loss, which is 0.026 dB/m, so
total propagation loss ~0.2 dB)
• Extinction ration 18 dB
• Coupling length 7.63 m
Nanophotonics 20
Contents
 Introduction to plasmonics
 Plasmonic waveguides
 Hybrid integration of plasmonic
waveguides and silicon wire waveguides
 Optical wireless interconnect network
based on plasmonic antennas
 Plasmonic light absorber
 Conclusions
Nanophotonics
Optical wireless interconnect
Artists view of integrated photonics device and
optical wireless interconnect node on a single
chip
Yuanqing Yang et al
Nanophotonics
Optical wireless interconnect
Port to Port (P2P)
Port-to-MultiPorts (P2MP)
Schematic diagram of a representative optical wireless broadcast network
Nanophotonics
Contents
 Introduction to plasmonics
 Plasmonic waveguides
 Hybrid integration of plasmonic
waveguides and silicon wire waveguides
 Optical wireless interconnect network
based on plasmonic antennas
 Plasmonic light absorber
 Conclusions
Nanophotonics
Loss: avoiding or utlizing?
 Plasmonic and metamaterial effects
Double split rings
are all based resonances (electric or
magnetic): loss associated
 Loss is mostly problematic for
waveguiding, or other applications.
 Or we can use the losses (absoprtion)!
Nanophotonics
2D optical metamaterial absorber
i=20
Fundamental Resonance
a = 310 nm.
Wx = 170 nm,
Wy = 230 nm,
t = 40 nm,
d = 10 nm
Many other groups are working on
similar structures
JM Hao et al
APL 96, 251104, 2010 In collaboration with W.J. Padilla (BC), L. Zhou (Fudan) Nanophotonics
26
Physics: Effective material parameters
At resonance peak (~1.58m):
e =  = 0.86+5.79i
JM Hao et al
APL 96, 251104, 2010
Impedance
: no reflection
Thick substrate: no transmission
Large imaginary parts: high absoprtion
Nanophotonics
Lithography-free broadband
visible light absorber
80nm-thick gold reflector
55nm-thick alumina layer
5nm top gold layer
Fabricated in a two-stage process:
1. Electron-beam-evaporation deposition
2. Thermal annealing
Large area 2.5 cm x 2.5 cm in size
M Yan et al 2014 J. Opt. 16 025002
Paper of the Week, Featured article
Side view
Nanophotonics 28
Colorful gold
Min Yan
Nanophotonics
Plasmonic light absorbers for
nanofabrications
Min Yan, Min Qiu
APL 2010-96-251104, ACS Nano 2012-6-2550,
Opt Express, 2011-19-14726, Nanoscale 2014-6-1756, ...
Nanophotonics
Metal–insulator–metal light
absorber: a continuous structure
Gold
Silver
FWHM ~ 2nm
Q ~ 310
FWHM ~ 7nm
Q ~ 90
M. Yan, J. Opt. 15, 025006 (2013)
Ding Zhao et al, Submitted
Nanophotonics
Conclusions
 Plasmonic devices could provide subwavelength confinement, which

could be very useful for photonic integration. However, loss is a big issue.
Possible solutions for avoiding large propagation losses in plasmonic
waveguides are
 Hybrid integration of silicon and plasmonic waveguides
 Wireless optical interconnect
 On the other hand, losses can be utilized for good: light absorption can

be enhanced through plasmonic resonance. Absorption bandwidth and
wavelength can be designed to almost any value in visible, infrared, and
even THz.
Photothermal effects due to light absorption can generate lots of
interesting new applications, also understanding of new physics:





thermo-optical switching
controlled thermal fusion
nanofabrication
nanoscale-thermaldynamics
…
Nanophotonics
Acknowlegement
 KTH: Assoc. Prof. Min Yan, Dr. Jiaming Hao, Dr. Jing
Wang, Dr. Yi Song, Xi Chen, Yiting Chen
 ZJU: Assoc. Prof. Qiang Li, Ding Zhao, Xingxing Chen,
Hanmo Gong
Nanophotonics

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