Transcript Miami University PHOTONIC CRYSTAL BASED WAVELENGTH DEMULTIPLEXING Meron Yemane Tekeste Physics Department, Miami University Oxford, OH 45056 Advisor: Dr.

Miami University
PHOTONIC CRYSTAL BASED
WAVELENGTH DEMULTIPLEXING
Meron Yemane Tekeste
Physics Department, Miami University
Oxford, OH 45056
Advisor: Dr. Jan M. Yarrison-Rice
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Miami University
Content
•
•
•
•
•
•
•
Augus 04, 2006
Introduction
Guiding Light using photonic crystal slab.
Cavities and Waveguides
Modeling and Simulation of WDDM devices
Device Fabrication
Preliminary Characterization
Conclusion
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Introduction
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•
•
•
•
•
Photonic crystals (PC) are artificial crystals, made up of dielectric materials with a
periodic variation in the dielectric constant along 1D, 2D or 3D. Allows us to
control light propagation within the crystal.
PC affect the property of photons in much the same way a semiconductor affects
the property of electrons.
A periodic variation of the dielectric constant in PC results in a photonic band gap
(PBG).
PBG is a range of frequencies for which light is forbidden to propagate inside the
crystal.
Wavelength Demultiplexing is differentiating multimode signals into single mode
signals.
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
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Three layer optical waveguide
Three layer optical waveguide;
– SiO2: n=1.46, 1.8m thick,
Cladding (Green).
– Si3N4: n=2.02, 200nm thick,
Core (Blue).
– Air, Cladding.
x3
x2
x1
 3 

  arctan  1
2 
2
 2 h  arctan 
10
Y(neff,h,ko);W(neff,q)
h=400nm
6
h=350nm
5
h=300nm
h=250nm
4
ℓ=1
h=200nm
3
ℓ=2
9.0
8
7

  

10.0
ℓ=2
9
Equation 1
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•
ℓ=0
2
8.0
7.0
ℓ=1
6.0
5.0
4.0
ℓ=0
3.0
2.0
1.0
1
0.0
0
1.4
1.3
1.4
1.5
1.6
1.7
1.8
1.9
2
2.1
1.5
1.6
1.7
1.8
1.9
2
2.1
2.2
neff
neff
Single light mode can be guided in this structure when the input
source free space wavelength ranges from 450 nm to 520 nm.
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
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A 2D triangular lattice photonic crystal with 75 nm radius cylindrical air holes
and 213 nm lattice constant covers a PBG range of 463nm < λ < 532nm :
(ωa/2πc)
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Photonic Band Gap (PBG)
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Air pores
n=1
2R
a
Silicon Nitride
n=2.02
a
x2
x1
G
X
M
G
k2
Μ
Γ
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Photonic crystal based Wavelength demultiplexing, Physics Department
Χ
k1
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Cavities and Waveguides
3
0.5
0.4
2.5
y (micron)
0.3
2
0.2
0.1
1.5
0.5
1
1.5
2
2.5
x (micron)
3
3.5
4
Changing a single air hole size, shape or/and dielectric constant a cavity for a
single frequency can be created
35
476.5nm
1.4
1.4
30
488.0nm
1.2
1.2
496.5nm
1.6
40
1
1
35
30
y
(mi 0.8
cro
n)
0.6
25
y
(mic
ron) 0.8
1
0.8
0.6
0.6
10
0.4
5
0.4
514.5nm
1.2
20
15
25
1.4
20
I/Io
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Removing a series of air holes or a single row, light can be guided efficiently.
15
0.2
0.4
10
0.2
0.2
0.2
0.4
0.6
0.8
1
x (micron)
1.2
1.4
5
1.6
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
x (micron)
0
0
Augus 04, 2006
25
50
75
100
R(nm)
Photonic crystal based Wavelength demultiplexing, Physics Department
125
150
Meron Yemane
175
200
<M|U>
τ
τ
α
t=219 nm
a= 6a (a= 213 nm)
Rcavity= 125 nm
99.4 % transmission for 514.5 nm line
0.16% transmission for 496.5 nm line
2.5
2.5
2
2.5
2
2
1.5
1.5
1.5
1
1
1
1
0.5
0.5
0.5
0.5
0.5
1
1.5
2
2.5
1
3
1.5
2
2.5
3
x (micron)
x (micron)
t=189 nm
a= 6a (a= 213 nm)
Rcavity= 140 nm
3% transmission for 514.5 nm line
98.5% transmission for 496.5 nm line
2.5
2.5
3
2
2
2.5
2.5
2
2
y (micron)
1.5
1.5
y (micron)
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Single Channel WDDM
1.5
1.5
1
1
1
1
0.5
0.5
0.5
0.5
0.5
0.5
1
1.5
2
2.5
x (micron)
Augus 04, 2006
1
1.5
2
2.5
3
3
Photonic crystal based Wavelength demultiplexing, Physics Department
x (micron)
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<M|U>
Two channel WDDM
Channel 2
1.03a
0.89a
20
R=125nm
1.03a
PBG
Mirror
R=135nm
1.03a
0.89a
2a
0.89a
4a
11a
Transmission Spectra
1
6
6
5
5
0.9
Channel 1
4
3
2.5
2
3
1.5
0.5
0.4
0.3
0.2
0.5
2
1
0.6
3
4
1
2
Channel 2
0.7
I/Io
y (micron)
0.8
y
(micron)
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Channel 1
0.1
0
5.68
1
5.78
5.88
5.98
6.08
6.18
6.28
f(THz)
1
2
3
4
x (micron)
5
6
1
2
3
4
x (micron)
5
6
Ch-1 (81.8%), Ch-2 (6%) Ch-1 (8.09%), Ch-2 (90.7%)
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Three Channel WDDM
1
2
16
3
14
2.5
2
0
0.89a
0.89a
2a
y (micron)
Source 514.5nm
2
1.03a
10
8
1.5
6
1
4
0.5
0
2
0
1
2
3
-2
-1
4
x (micron)
5
6
1
2
7
2
1.5
1
0
0.5
a
0.84a
0
-4
-3
0
s (micron)
3
4
Ch-1 (95%), Ch-2 (4.1%), & Ch-3 (0.9%)
1
2
15
10
1
5
0.5
0
1
2
3
4
x (micron)
5
6
7
1.5
1
0.5
0
-4
-3
-2
-1
0
s (micron)
1
2
3
4
Ch-1 (3.7%), Ch-2 (86.4%), & Ch-3 (11.3%)
Augus 04, 2006
y (micron)
2
1.5
2
12
10
2.5
2
8
1.5
6
1
4
0.5
2
0
0
1
2
3
4
x (micron)
5
6
7
1.5
s (micron)
y (micron)
2.5
0
1
3
Source 476.5nm
3
Source 496.5nm
Miami University
12
2
1
0.5
0
-3
-2
-1
0
s (micron)
1
2
3
Ch-1 (5.1%), Ch-2 (13.3%), & Ch-3 (80.4%)
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Device Fabrication
Miami University
Fabrication Process
1.
2.
3.
4.
5.
6.
7.
8.
Main Structure
PMMA resist is coated
10nm Gold is sputtered.
Ebeam exposure
Gold is etched using KI/I.
PMMA resist is developed.
Plasma Etching
Final structure.
Gold (10nm thick)
PMMA (400nm thick)
Silicon Nitride (200nm thick)
Silicon dioxide (1800nm thick)
Silicon Substrate
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Miami University
Fabrication Results
Photonic crystal region with 125 nm radius cavity.
Photonic crystal region with 140 nm radius cavity.
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Miami University
Two Channel WDDM
SEM image of a two channel wavelength demultiplexer.
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Miami University
Waveguide Coupler
Waveguide funnel to couple light source to the wavelength demultiplexer.
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Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
3
2.5
2.5
2.5
2
2
2
1.5
1.5
1
1
1.5
1
0.5 1
Augus 04, 2006
3.5
3
3
y (micron)
• Random
• Waveguide
3.5
3.5
y (micron)
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Fabrication Error: air pore inconsistency
1.5 2 2.5 3 3.5 4 4.5
x (micron)
0.5
0.5
1
Photonic crystal based Wavelength demultiplexing, Physics Department
1.5
2
2.5
3
x (micron)
3.5
Meron Yemane
4
4.5
<M|U>
Horizontal Shift
New
1.2
0.9
Output
New
0.8
1
0.7
0.8
I/I0
0.6
0.5
0.6
0.4
0.4
0.3
0.2
0.2
0.1
0
0
0
0
50
100
150
200
250
300
350
100
150
200
250
t(nm)
1.5
1
1
y (micron)
1.5
y (micron)
50
400
1.5
2
1.5
1
1
0.5
0.5
0.5
0.5
1
1.5
2
2.5
x (micron)
3
3.5
4
4.5
0.5
0.5
5
1
1.5
2
2.5
x (micron)
3
3.5
4
4.5
5
1.5
3
1.5
2
2
1
1.5
0.5
y (micron)
2.5
y (micron)
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Fabrication Error: Stitching error
1
1.5
1
0.5
1
0.5
0.5
0.5
Augus 04, 2006
1
1.5
2
2.5
3
x (micron)
3.5
4
4.5
5
0
0.5
1
1.5
2
2.5
x (micron)
3
3.5
4
4.5
Photonic crystal based Wavelength demultiplexing, Physics Department
5
Meron Yemane
<M|U>
Fiber
Coupler
GRIN
Lens
Argon Laser
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Optical Characterization
WDDM
device
PIN
ND
Stage
PI
N
CCD
Fiber
Coupler
Objective
lens
Filter
wheel
TE Poalrizer
Mirror
Augus 04, 2006
Beam
Splitter
Wave Meter
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Miami University
Conclusion
• Efficient photonic crystal based wavelength demultiplexer is
modeled.
• The fabrication process and its results up to the development
process are identified.
• Correct dose rate and designedly corrected radius of the
regular crystal and the cavities are identified.
Future Work:
– Etching process
– Improving the coupling method with input source
– Testing the device
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Miami University
Thank You!!
Questions?
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
EM wave propagation in a dielectric medium
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Maxwell’s Equation
   (r ) E (r )  0
  D(r , t )  4
Separation of
variables
  B(r , t )  0
1 B(r , t )
0
c t
  E (r ) 
1 D(r , t ) 4

J
c t
c
  H (r ) 
  E (r , t ) 
io
H (r )  0
c
i (r )
E (r )  0
c
For macroscopic and isotropic medium {D(r)=ε(r)E(r)}
For a low-loss dielectrics (ε(r) is real)
No source of light inside the photonic crystal ( J=0, ρ=0)
  H (r , t ) 
•
•
•
  H (r )  0
Boundary condition
n  ( E2  E1 )  0
n  ( H 2  H1 )  0
( D2  D1 )  n  0
( B2  B1 )  n  0
Augus 04, 2006
Tangential field component
Normal field component
Photonic crystal based Wavelength demultiplexing, Physics Department
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<M|U>
Miami University
Three layer Optical waveguide
• Uniform along x1, x2
index difference
along x3, therefore
field components
along x1 and x2 will
be constant
• Wave equation:
 2 E x1
x3
2


 k 2  k x22 E x1  0
Or
 2 E x1
x3
Augus 04, 2006
2


2
 k o ni2  neff
E x1  0
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
2
1.5
1.5
2
y(μm)
2.5
1.5
1
1
1
0.5
2.5
2
2
1.5
1.5
1
1
0.5
1
0.5
0.5
0.5
1
1.5
2
x (micron)
2.5
0.5
3
1
1.5
2
x (micron)
2.5
1.5
2
x (micron)
2.5
3
0.5
7.2% (488 nm)
2.5
2.5
1
3
5.1% (495.5nm)
86%(514.5nm)
1
1.5
2
x (micron)
2.5
3
12.1% (476.5nm)
2.5
2.5
3
3
1.5
2
1.5
1.5
1
1
1
1
0.5
2
1
1.5
2
x (micron)
2.5
1
1.5
2
x (micron)
2.5
3
2.5
2
1.5
1.5
1
1
0.5
1
1.5
2
x (micron)
2.5
3
0.5
7.9% (488 nm)
1
1.5
2
x (micron)
2.5
3
10.2% (476.5nm)
2.5
2.5
0.5
0.5
0.5
87.2% (495.5nm)
2.5
1.5
0.5
0.5
3.4%(514.5nm)
1.5
1
0.5
3
2
1
0.5
0.5
2
2.5
y (micron)
1.5
y (micron)
2
2.5
2
2.5
y (micron)
2
0.5
2.5
6
1.5
1
2
2
5
4
1.5
3
2.5
2
1.5
1.5
2
0.5
1
0.5
1
1
0.5
1
1.5
2
x (micron)
2.5
3
84.2%(514.5nm)
1
1.5
2
x (micron)
2.5
3
1.4% (495.5nm)
2
2.5
2
1.5
1.5
1
1
1
0.5
0.5
0.5
3
3
y (micron)
1.5
y (micron)
2
y (micron)
2
0.5
Augus 04, 2006
1.5
0.5
0.5
0.5
t=219 nm
a= 6a
Rcavity= 125 nm
2
1.5
1
0.5
t=189 nm
a= 6a
Rcavity= 135 nm
2.5
2
y (micron)
3
2.5
2
1.5
1
0.5
3
2
y (micron)
2.5
2.5
y (micron)
t=219 nm
a= 6a (a= 213 nm)
Rcavity= 125 nm
2.5
2.5
y (micron)
Miami University
Single Channel WDDM
1
0.5
0.5
0.5
1
1.5
2
x (micron)
2.5
3
24.6% (488 nm)
Photonic crystal based Wavelength demultiplexing, Physics Department
0.5
1
1.5
2
x (micron)
2.5
3
27.8% (476.5nm)
Meron Yemane
<M|U>
Electron beam exposure
incident
beam
Miami University
BSE
SEII
Augus 04, 2006
SEI
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Proximity Correction
 1  r22   r2
1
 2 ea  2 e
f (r ) 
 1     a


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2



Forward scattering
1,0
Backward scattering
D/Do
0,8
0,6
0,4
0,2
0,0
0
500
1000
1500
2000
2500
3000
3500
4000
r(nm)
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Miami University
Movie for 514.5nm source
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>
Miami University
Movie for 496.5nm source
Augus 04, 2006
Photonic crystal based Wavelength demultiplexing, Physics Department
Meron Yemane
<M|U>