1. Trends in Future
Communications
International Workshop
CPqD - Campinas
Renato Cunha Rabelo, PhD – IEAv-DCTA
24/02/2014

2. Outline
• IEAv/DCTA
• Lithium Niobate Filters

4. IEAv
EAH ENU EFA EFO ESTEGI

5. IEAv
EAH ENU EFA EFO ESTEGI
Institute for Advanced Studies

6. IEAv
EAH ENU EFA EFO ESTEGI
Institute for Advanced Studies
Mission: Build scientific knowledge and develop strategic technology capable
of strengthening Brazilian aerospace competence.

7. IEAv
EAH ENU EFA EFO ESTEGI
Photonics Division

8. IEAv
EAH ENU EFA EFO ESTEGI
Photonics Division
Generate, control and detect light

9. IEAv
EAH ENU EFA EFO ESTEGI
EFO-LEFO-SEFO-O

10. PhDs Masters Graduates Technician
s
EFO-L 07 03 03 04
EFO-O 04 02 0 03
EFO-S 05 05 0 03
Total EFO 17 10 03 10
MANPOWER
40

11. Collaborators
Postdocs MSc / PhD
Students
Graduates /
MSc
Students
Undergrad
Students
EFO-L 01 10 04 06
EFO-O 1 0 0 10
EFO-S 02 0 2 02
Total EFO 04 10 06 18
38

12. Spectral Slicing Filters in Titanium
Diffused Lithium Niobate (Ti:LiNbO3)
Waveguides

13. WDM
Fiber Optic Communication link
λ1ReceiverTransmitterλ1
Optical Fiber
Transmitterλ2
Transmitterλn-1
Transmitterλn
λ2Receiver
λn-1Receiver
λnReceiver
..
.
..
.
MUX
DEMUX

14. DWDM Channels
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7
0.0
0.2
0.4
0.6
0.8
1.0
+6-6 -5 -4 -3 -2 -1 +10 +3+2 +5+4Amplitude(a.u.)
Normalized Frequency (ν-ν0
) X 100 GHz)

15. TE-TM Mode Conversion:
LiNbO3
Ti diffused
Waveguide
xˆ yˆ
zˆ
TE
TM
L
SiO2 Strain inducing grating
Λ

16. TE-TM Mode Conversion:
unconvconv
conv
PP
P
PCE
+
=























 ∆
−





 ∆
+
=





∆∆
∆−∆−
)0(
)0(
sin
2
cossin
sinsin
2
cos
)(
)(
2/2/
2/2/
B
A
yjyeyje
yjeyjye
yB
yA
yjyj
yjyj
δ
δ
δδ
δ
κ
δ
δ
κ
δ
δ
δ
)()(
0
0 TMTETMTE nnnnv
c
−
=
−
=Λ
λ
0
2)(2
=
Λ
±
−
=∆
ππ
c
nnv TMTE
Λ
±
−
=∆
ππ 2)(2
c
nnv TMTE












=





)0(
)0(
cossin
sincos
)(
)(
B
A
LLj
LjL
LB
LA
κκ
κκ
LL
L
κκ
κ
22
2
cossin
sin
+
= Lκ2
sin=

17. TE-TM Mode Conversion:
-12 -8 -4 0 4 8 12
0.0
0.2
0.4
0.6
0.8
1.0PolarizationConversionEfficiency
Normalized Frequency ((ν−ν0
) x 100 GHz)

18. Fabrication Steps
Titanium Deposition
(DC sputtering)
LiNbO3
Ti t
Patterning
(Photolithography)
Diffusion
LiNbO3
Ti t
LiNbO3
Ti
LiNbO3
Heat
and
Time
LiNbO3
SiO2
Silica Deposition
(E-beam evaporation)
@ High Temp
Cool-down to
Room Temp.LiNbO3
SiO2
Surface Strain
build-up
αSiO2
< α LiNbO3
Patterning
(Photolithography)LiNbO3
SiO2
(Side view) LiNbO3
SiO2SiO2SiO2SiO2 SiO2 SiO2
Λ

19. Conversion Efficiency
Test Setup
Er+
doped fiber
Laser Diode
Pump @ 980 nm
OSA
Sample under test
Objective
WDM 980/1550
coupler
PZ fiber
Objective
Polarizer
Amplified Spontaneous Emission
light source
Isolator

20. Conversion Efficiency
Test Setup

21. Conversion Efficiency
Test Results (Uniform Grating)
TM → TM
TM → TE
TE → TE
TE → TM

22. Conversion Efficiency
Test Results (Uniform Grating)
22
2
)()(
)(
zBzA
zB
utputr at the oTotal powe
ion powerpolarizatConverted
PCE
+
==
1528 1530 1532 1534 1536 1538 1540
0.0
0.2
0.4
0.6
0.8
1.0
W/G 5 - Linear Scale
Room Temperature
500 elements
TE input/TM output
TM input/TE output
Theoretical Response
PolarizationConversionEfficiency
Wavelength (nm)
Conversion Efficiency =
99.8%
@ 1533 nm

23. Device Fabrication
Conversion Efficiency
•Coupling coefficient had to be adjusted
dxdzEE TM
pert
TE
∫
∞
∞−
∆⋅= εκ
Critical Parameters:
1. Titanium film thickness → Mode Profiles
2. Titanium in-diffusion time and temperature → Mode Profiles
3. SiO2 strain film thickness and deposition temperature → Strain field
Conversion Mechanism (index modulation) → Static strain-optic (elastooptic) effect

24. Conversion Efficiency
Uniform Grating ( 500 spatial periods)
• 1250 Å Ti film deposition
• Photolithography to define Waveguides (Ti-strips)
• 13 h diffusion @ 1035
o
C and wet atmosphere
• 1.7 µm SiO2 strain film deposited @ 389
o
C
• Photolithography to define strain grating (500 periods) @ room temperature
After many trials:

25. Conversion Efficiency
Temperature Tuning (Uniform Grating)
1524 1526 1528 1530 1532 1534 1536 1538 1540 1542 1544 1546 1548
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
24.5
o
C 22.5
o
C 20.0
o
C
17.7
o
C 16.6
o
C 15.2
o
C
14.4
o
C
Temperature tuning
PolarizationConverisonEfficiency
Wavelength (nm)
14 16 18 20 22 24 26
1528
1530
1532
1534
1536
1538
1540
1542
1544
Peak wavelengths vs Temperature
and
Linear Regression
dλ/dT = - 1.3419 nm /
o
C
ConvertedPeakwavelength(nm)
Temperature (
o
C)

26. Sparse Grating:
L1
L2 L3 L4 L5 L6
L L L LL LiNbO3
Ti diffused
Waveguide
xˆ yˆ
zˆ

27. Sparse Grating:
Propagation Matrix
( )














=





−
−
−−
−
−
inTE
inTM
Lnn
c
j
outTE
outTM
E
Ee
E
E gTEgTM
10
0
ω














=





−
−
−
−
−
inTE
inTM
outTE
outTM
E
Ez
E
E
10
01
Combining Effects (Coupling and Propagation)














=





=





−
−
−
−
−
−
−
inTE
inTM
R
R
inTE
inTM
nn
outTE
outTM
E
E
zAzjB
zjBzA
E
E
PCPCPPCC
E
E
)()(
)()(
121 
c
nnL
T
gTMgTE )( −
=
Tj
ez ω
=

28. Z Transform
s-plane z-planes-plane z-plane

29. Z Transform
∏=
−
−=
n
i
i zzzP
1
1
)1()(
-1 -0.5 0 0.5 1
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
Roots of B5
(z)
Re(z)
Im(z)

30. Filter Theoretical Frequency Response
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7
0.0
0.2
0.4
0.6
0.8
1.0
PolarizationConversionEfficiency
Normalized Frequency (ν-ν0
) X 100 GHz)
∆νFSR

31. DWDM Channels
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7
0.0
0.2
0.4
0.6
0.8
1.0
+6-6 -5 -4 -3 -2 -1 +10 +3+2 +5+4Amplitude(a.u.)
Normalized Frequency (ν-ν0
) X 100 GHz)

32. Filtered DWDM
Channels
-7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7
0.0
0.2
0.4
0.6
0.8
1.0
-6 +60
Amplitude(a.u.)
Normalized Frequency ((ν-ν0
) X 100 GHz)

33. Filter Theoretical Frequency Response
-4 -3 -2 -1 0 1 2 3 4
0.0
0.2
0.4
0.6
0.8
1.0
PolarizationConversionEfficiency
Normalized Frequency ((ν-v0
)/∆νFSR
)

34. Electrooptically Tunable Sparse Grating
Filter
L1 L2 L3 L4 L5 L6
L L L LL LiNbO3
Ti diffused
Waveguide
Electrodes
L1 L2 L3 L4 L5 L6
L L L LL LiNbO3
Ti diffused
Waveguide
L1 L2 L3 L4 L5 L6
L L L LL LiNbO3
Ti diffused
Waveguide
Electrodes

35. Device Fabrication / Electrodes
Fabrication Steps
Titanium Deposition
(DC sputtering)
LiNbO3
Ti t
Patterning
(Litho and Etching)
Diffusion
LiNbO3
Ti t
LiNbO3
Ti
LiNbO3
Heat
and
Time
LiNbO3
Photolithography
(Image Reversal)
E-Beam
3 metalsLiNbO3
Lift-Off
LiNbO3
Silica Deposition
(E-beam evaporation)
@ High Temp
Cool-down to
Room Temp.
Surface Strain
build-up
αSiO2
< α LiNbO3
Patterning
(Litho and Etching)LiNbO3
SiO2
LiNbO3
SiO2
LiNbO3
SiO2

36. Device Fabrication / Electrodes
(Side view) LiNbO3
SiO2
Λ
SiO2 SiO2
SiO2
Electrodes

37. Conversion Efficiency
Test Setup
Er+
doped fiber
Laser Diode
Pump @ 980 nm
OSA
Sample under test
Objective
WDM 980/1550
coupler
PZ fiber
Objective
Polarizer
Amplified Spontaneous Emission
light source
Isolator

38. Conversion Efficiency
Test Results (Sparse Grating)
TE → TE
TE → TM TM → TE
TM → TM

39. Conversion Efficiency
Test Results (Sparse Grating)
)9.131(044.13 GHznmdB =∆λ
1515 1518 1521 1524 1527 1530 1533 1536 1539 1542
-30
-28
-26
-24
-22
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
TE input/TM output T= 25.0
o
C
TM input/TE output
Theoretical Response
PolarizationConversionEfficiency(dB)
Wavelength (nm)
%96≅PCE

40. Test Results (Sparse Grating)
Thermal Tuning
1515 1520 1525 1530 1535 1540 1545 1550 1555
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
14
o
C
25
o
C
PolarizationConversionEfficiency
Wavelength (nm)
12 14 16 18 20 22 24 26 28 30
1524
1526
1528
1530
1532
1534
1536
1538
1540
1542
TM to TE conversion
TM to TE data linear regression
TE to TM conversion
TE to TM data linear regression
CenterPeakWavelength(nm)
Temperature (
o
C)
CdTd o
nm/0.1−=λ

41. Test Results (Sparse Grating)
Voltage Tuning
input)(TMnm/V045.0=dVdλ
1520 1530 1540
0.0
0.2
0.4
0.6
0.8
1.0
70 V
-70 V
PolarizationConversionEfficiency
Wavelength (nm)
-80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
TM input/TE output
Linear fit TM input data
TE input/TM output
Linear fit TE input data
Wavelength(nm)
Applied Voltage (V)
input)(TEnm/V039.0=dVdλ
99.4%91.7%

42. Polarization Independent Sparse Grating
Filter
InputInput
No Output
πφ =∆

43. ...
...
2
Λ
2
Λ
......
......
2
Λ
2
Λ
InputInput
Output
πφ 2=∆
Polarization Independent Sparse Grating Filter

44. Polarization Independent Sparse Grating
L1 L2 L3
L L L L L
L3 L2 L1
LiNbO3
L1 L2 L3
L L L L L
L3 L2 L1
LiNbO3
L1 L2 L3
L L L L L
L3 L2 L1
LiNbO3

45. Test Results - Polarization Independent Sparse Grating
Er+
doped fiber
Laser Diode
Pump @ 980 nm
WDM 980/1550
coupler
Er ASE light source
PZ fiber
Optical
Power
Meter
Ge Photodetector
Sample
Under
Test
Current
Source
Output Fiber
Isolator
Er+
doped fiber
Laser Diode
Pump @ 980 nm
WDM 980/1550
coupler
Er ASE light source
PZ fiber
Optical
Power
Meter
Ge Photodetector
Sample
Under
Test
Current
Source
Output Fiber
Isolator

46. Test Results - Polarization Independent Sparse Grating

47. Test Results - Polarization Independent Sparse Grating
1518 1521 1524 1527 1530 1533 1536 1539 1542
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
TM input
TE input
Theoretical Response
NormalizedOutputSpectrum(dB)
Wavelength (nm)

48. Test Results - Polarization Independent Sparse Grating
Thermal Tuning
1515 1520 1525 1530 1535 1540 1545 1550 1555
0.0
0.2
0.4
0.6
0.8
1.0
TE input @ 14
o
C
TE input @ 27
o
C
NormalizedFilterResponse
Wavelength (nm)
10 12 14 16 18 20 22 24 26 28 30
1524
1526
1528
1530
1532
1534
1536
1538
1540
1542
1544
TM input
Linear Fit of TM data
TE input
Linear Fit of TE data
Wavelength(nm)
Temperature (
o
C)
CdTd o
nm/0.1−=λ

49. Future Work
• 4-Port Asymmetric MZI
L1 L2 L3
L L L L L
L3 L2 L1
LiNbO3
L1 L2 L3
L L L L L
L3 L2 L1
LiNbO3

50. Future Work
• Generic “all-zero” synthesis
L1 L2 L3 L4
L5 L6
B C D EA LiNbO3
Ti diffused
Waveguide
Electrodes
L1 L2 L3 L4
L5 L6
B C D EA LiNbO3
Ti diffused
Waveguide
L1 L2 L3 L4
L5 L6
B C D EA LiNbO3
Ti diffused
Waveguide
Electrodes

51. Thank you !
rcrabelo@ieav.cta.br