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Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Photonics on-chip Michal Lipson
School of Electrical and Computer Engineering
Cornell University
nanophotonics.ece.cornell.edu
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Outline
• Motivation and wave guiding theory
(quantum optics on chip)
• Resonators and applications of waveguides
on-chip
• Changing properties of light using
resonators (analogous to quantum optics on-
chip)
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Photonics Drives Telecom
10-2
100
102
104
106
108
1010
1012
1014
1880 1900 1920 1940 1960 1980 2000 2020 2040
Rel
ativ
e In
form
atio
n C
apac
ity (
bit/s
)
Year
Telephone lines first constructed
Carrier Telephony first used 12 voicechannels on one wire pair
Early coaxial cable links
Advanced coaxial and
microwave systems
CommunicationSatellites
Single channel (ETDM)
Multi-channel(WDM)
OPTICAL FIBER SYSTEMS
~10Mbps.Km
We are experiencing this drive on-chip!
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Luxtera CMOS Photonics Technology
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Kimerling, 1997
Silicon photonics on-chip
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Silicon photonics for multi-core
interconnect
Photonic Network Interconnect Plane (includes optical devices, electronic drivers & amplifiers and electronic control network)
Optical Off-chipInterconnects
Memory Plane
Memory Plane
Memory Plane
BEOL verticalelectrical interconnects
Processor Plane w/ local memory cache
Photonic Network Interconnect Plane (includes optical devices, electronic drivers & amplifiers and electronic control network)
Optical Off-chipInterconnects
Memory Plane
Memory Plane
Memory Plane
BEOL verticalelectrical interconnects
Processor Plane w/ local memory cache
Bergman-Columbia, J. Kash, IBM
Opt
ical
I/O
Opt
ical
I/O
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Why light is guided?How light is guided?
Total internal reflection!
θθθθ> θθθθcrit=sin-1(nL/nH)
The larger is the index-the easier it is to guide
θθθθ
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Is it a ray or is it a wave?
Ray picture
Wave picture
E~e-γx
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Wavector of propagation
• Light propagating in a medium with index
n:
• vp=c/n
• λ=λo/n
kon kf
β
β2 =(kon+ kf)2
β ≡koneff
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Different modes in a waveguide
kon
β
β2 =(ko2n2- kf
2)
E ~ cos kfx e-γx
γ =sqrt(β2-ko2nclad
2)
kf
Lower order
Higher order
β= koneff> koncladd and < konslab
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Bending light on-chip
Work only with high confinement,
single mode waveguides!
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
“Slot-Waveguide” for High Confinement in sub-
wavelength regions!
nH nH
ws wh
h nS
wh
nC
x
y z
nH = 3.48
nC = nS = 1.46
wS = 50 nm
wh = 180 nm wh = 180 nm
nH = 3.48
0
1.0
Col
or s
cale
nH = 3.48
nC = nS = 1.46
wS = 50 nm
wh = 180 nm wh = 180 nm
nH = 3.48
0
1.0
Col
or s
cale
� True eigenmode
TE-like mode
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Si Si
E-Field Distribution
BBAA
rr
BA
EnEn
nED
DDSdD
,
2
,
2
2
0
,,
,
0
⊥⊥
⊥⊥
=⇒
==
=⇒=⋅∫εεε
rr
rr
(nA > nB) � E⊥,B > E⊥,A
x
Si Si
x
nH = 3.48
nC = nS = 1.46
wS = 50 nm
wh = 180 nm wh = 180 nm
nH = 3.48
0
1.0
Col
or s
cale
nH = 3.48
nC = nS = 1.46
wS = 50 nm
wh = 180 nm wh = 180 nm
nH = 3.48
0
1.0
Col
or s
cale
V.Almeida, and M. Lipson et al,, Optics Letters 29, 2387(2004).
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Fabrication of Slot-Waveguide and
Measurement of Effective Index
slot
nH nH
ws wh
h nS
wh
nC
x
y z
2
0
22
knn xCeff
γ+≅
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
1 .5 0 1 .5 2 1 .5 4 1 .5 6 1 .5 8 1 .6 0 1 .6 2 1 .6 40 .0
0 .2
0 .4
0 .6
0 .8
1 .0
Qua
si-T
M T
rans
mis
sion
(a.u
.)
W a v e le n g th ( µµµµ m )
1 .5 0 1 .5 2 1 .5 4 1 .5 6 1 .5 8 1 .6 0 1 .6 2 1 .6 40 .0
0 .2
0 .4
0 .6
0 .8
1 .0
Qua
si-T
E T
rans
mis
sio
n (a
.u.)
W a ve le n g th (µµµµ m )
TE
1.54 1.56 1.58 1.60
2.2
2.4
2.6
2.8
Wavelength (µµµµm)
Gro
up
Ind
ex
TE (calculated)TM (calculated)TM (experimental)TE (experimental)
Slot-Waveguides for
Highly Integrated Photonics
TM
20 µµ µµ
m
A. Scherer, SPIE, Denver, Aug 2004
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Slots for sensing
optical input
optical output
gas input gas output
slot
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
High index contrast leads to high
confinement kon
kf
β
γ =sqrt(β2-ko2ncladd
2)
High confienmentLow confienment
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
High confinement waveguides for functional
devices
Light
� Intensity in the waveguides can be orders of magnitude higher than the
intensity in the core of single mode optical fiber.
� Nonlinear optical effect can be excited with moderate optical power in
short distances.
Si
SiO2
450 nm ×××× 250 nm
Silicon waveguides:
•High index contrast (very small waveguides: 3 orders of magnitude light
enhancement when compared to fibers)
•Compatible with CMOS microelectronics.
•Ability of large-scale integration.
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
BOx: 3µm
Si: 250nm
Si Substrate
BOx: 3µm
Si Substrate
BOx: 3µm
Width = 450nm
Ebeam Lithography EBeam Resist
Oxide Deposition
Etching using RIE
Fabrication
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Orientation of the waveguides
Highly polarization dependent
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Why not every angle (wavector) can
propagate?
k on
2konhcos θθθθ+Ødown+ Øup=q2ππππ q=1,2,3…..
or cos θθθθ~q ππππ/nkoh
θθθθ
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
A Very small waveguide
cos θθθθ~q ππππ/nkoh
If q=1 and h small
cos θθθθ~ ππππ/nkoh is large (small angle)
k onθθθθ
Small angle means very large evanescent field!
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Silicon waveguide
Fiber
Light
~3% transmission
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Naive Solution
0.5 µ µ µ µm
10 µ µ µ µm
cm
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Inverse Taper
0.5 µ µ µ µm
10 µ µ µ µm20µm
NTT, IBM
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
0.5 µ µ µ µm
10 µ µ µ µm20µm
Inverse Taper
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Substrate
x
z
y
Substrate (Si)
Optical Fiber
MFD = 4.9 µm ws = 120 nm
h = 250 nm
Cladding (SiO2)
Simulations
95% efficiency
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Fabrication
<1dB losses
200 nm
CouplerWaveguide
Almeida, V. R., Panepucci, R. R., and M. Lipson, Optics Letters, 28, 1302 (2003).
Cornell Nanophotonics Group Cornell Nanophotonics Group �������� http://http://nanophotonics.ece.cornell.edunanophotonics.ece.cornell.edu
Summary
Motivation
Wave guiding theory
Slot waveguide
Fiber to waveguide coupler
High confinement waveguides/fabrication
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