OFC 2019
March 3-7, 2019, San Diego
Electrically programmable equivalent-phase-shifted waveguide Bragg grating for
multichannel signal processing
Weifeng Zhang and Jianping Yao
Microwave Photonics Research LaboratorySchool of Electrical Engineering and Computer Science
University of Ottawa
2
Outline
Introduction to equivalent phase-shifted (EPS) Bragg gratings
EPS Bragg grating design and performance evaluation
Multichannel signal processing
Conclusion
3
Introduction – fiber Bragg gratings
oeffn λ=Λ2Bragg condition
K. O. Hill, Y. Fujii, D. C. Johnson, and B. S. Kawasaki, “Photosensitivity in optical fiber waveguides: Application to reflection filter fabrication,” Appl. Phys. Lett., vol. 32, pp. 647–649, 1978.
4
Introduction – fiber Bragg gratings
Phase-shifted fiber Bragg grating Reflection spectrum
Uniform fiber Bragg grating
Input Transmission
Reflectionwavelength
wavelength
wavelength
periodic index modulation
K. O. Hill, Y. Fujii, D. C. Johnson, and B. S. Kawasaki, “Photosensitivity in optical fiber waveguides: Application to reflection filter fabrication,” Appl. Phys. Lett., vol. 32, pp. 647–649, 1978.
oeffn λ=Λ2
5
Introduction – waveguide gratings
Uniform waveguide Bragg grating (through edge corrugations)
Conventional phase-shifted waveguide Bragg grating
grating pitch phase-shifted block
Need very high fabrication accuracy (nm range)
W. Zhang, W. Li, and J. P. Yao, IEEE Photon. Technol. Lett. 26, 2383-2386, (2014)
6
Equivalent-phase-shifted (EPS) waveguide Bragg grating
Uniform grating
Sampling function
EPS grating
P+∆Psampling period P
Introduction – waveguide gratings
S. Blais and J. P. Yao, J. Lightw. Technol. 27, 1147-1154 (2009)
7
Introduction – waveguide gratings
Grating Phase-shifted block length
Conventional phase-shifted grating ¼ λ Need high
fabrication accuracy (nm range)
EPS grating hundreds of λ Reduced by three orders of magnitude (µm range)
J. Sun, et. al, IEEE Photon. Technol. Lett. 24, 25–27 (2012)
After fabrication, non-programmable
8
Programmable EPS grating design
9
Programmable EPS grating design
Wafer Grating Doping Independent Electrodes
Voltage Control
Programmable EPS Grating
10
Programmable EPS grating design
11
Performance evaluation: static state
1525 1530 1535 1540 1545 1550 1555 1560-60
-50
-40
-30
-20
Optic
al po
wer (
dBm)
Transmisson Reflection(a)
Wavelength (nm)1546 1548 1550 1552 1554 1556 1558 1560
-60
-50
-40
-30
-20
Optic
al po
wer (
dBm)
Transmisson Reflection
+11+9+7+5+1 +3
(c) 2.4 nm
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Performance evaluation：independent tuning
1548.9 1549.1 1549.3 1549.5Wavelength(nm)
-36
-32
-28
-24 Reverse biasForward
bias
Opt
ical
pow
er
(dBm
)
-19 V-12 V-8 V-4 V
0 V0.7 V0.9 V1.0 V
1548.9 1549.1 1549.3 1549.5Wavelength(nm)
-36
-30
-24 Reverse biasForward
bias
-19 V-12 V-8 V-4 V
0 V0.7 V0.9 V1.0 VO
ptic
al p
ower
(d
Bm)
Applying and tuning a bias voltage to the PN junctions in the on-modulation grating sections
Applying and tuning a bias voltage to the PN junctions in the off-modulation grating sections
+3rd channel spectral response tuning
+3rd channel spectral response tuning
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Performance evaluation: joint tuning
1548.9 1549.1 1549.3 1549.5Wavelength(nm)
-38
-34
-30
-26
-22
Opt
ical
pow
er (d
Bm) Reverse
biasForward
bias
(a) -19 V-15 V-12 V-8 V-4 V0V
0.7 V0.9 V1.0 V
1549.08 1549.16 1549.24
Wavelength (nm)
-33
-30
-27
-0.6
-0.2
0.2
0.6
1549.08 1549.16 1549.24
Opt
ical P
ower
(dBm
)Ph
ase
(rad
)
0 V 0 V-7.0 V 0.86 V
-11.5 V 0.92 V-19 V 1.02 V
on- off-
0 V 0 V-7.0 V 0.86 V
-11.5 V 0.92 V-19 V 1.02 V
on- off-
1. The two bias voltages are simultaneously and synchronously changed from −19 to +1 V.
2. Tuning the extinction ratio whilethe 3rd channel notch wavelength ismaintained unchanged for differentbias voltages.
+3rd channel spectral response tuning
Extinction ratiochange:from 6.4 to 4.5
Phase jump change:from 1.0 to 0.48
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Multichannel signal processing: temporal differentiation
-800 -400 0 400 800Time (ps)
0
0.4
0.8
1.2
Inte
nsity
(n.u
.)
Exp.Theo.
(b)
-800 -400 0 400 800Time (ps)
0
0.4
0.8
1.2
Inte
nsity
(n.u
.)Exp.
Theo.(a)
A multichannel temporal differentiator with a channel spacing of 2.4 nm is experimentallydemonstrated. The figure shows the measured temporally differentiated pulses corresponding to adifferentiation order of (a) 0.53 at the +5th channel, and (b) 0.74 at the +7th channel.
Differentiation order： 0.53at the +5th
channel
Differentiation order： 0.74at the +7th
channel
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Conclusion
A silicon-based on-chip electrically programmable EPSwaveguide Bragg grating was designed, fabricated andexperimentally demonstrated.
By incorporating the programmable EPS grating in a microwavephotonic system, a multichannel microwave photonicdifferentiator was experimentally demonstrated.
Incorporating more independent control sections would enrichthe functionality.
Thank you
16
Acknowledgements
CMC Microsystems NSERC SPG program
