fully reconfigurable waveguide bragg gratings for ...jpyao/mprg/reprints/ofc2019-w3bi...able to...

OFC2019

OFC2019

March 3-7, 2019, San Diego

Fully reconfigurable waveguide Bragg gratings for programmable photonic

signal processing

Jianping Yao and Weifeng Zhang

Microwave Photonics Research LaboratorySchool of Electrical Engineering and Computer Science

University of Ottawa

2

OFC2019

Photonic Integrated Circuits - Material Systems Silicon photonic gratings– Chirped Bragg gratings for RF generation– Phase-shifted gratings for temporal differentiation– Electrically tunable Fabry–Perot Bragg grating for signal processing– Fully reconfigurable waveguide Bragg gratings for programmable

photonic signal processing– Electrically programmable equivalent-phase-shifted waveguide Bragg

gratings for multichannel signal processingConclusion

Outline

3

OFC2019

Three material systems: 1) Indium Phosphide (InP) 2) Silicon Nitride (Si3N4)3) Silicon on Insulator (SOI)

1) InP: Able to monolithically integrate both active and passive photonic

components High loss, and large sizeDifficulty to integrate with electronics

Material systems

4

OFC2019Material systems2) Si3N4: Very low loss, <0.2 dB/cm No active components such as light sources, modulators, amplifiers and

photodetectors can be supported, thus full monolithic integration is hard to achieve

3) SiP: A technology that allows optical devices to be made economically using the standard

and well-developed CMOS fabrication processMost of the optical components, both passive and active, can be fabricated The key advantages include much smaller footprint, low loss, and simple

fabrication process and can be integrated with electronics (analog and dgital) No optical amplification and light emission

5

OFC2019

Photonic Integrated Circuits - Material Systems Silicon photonic gratings– Chirped Bragg gratings for RF generation– Phase-shifted gratings for temporal differentiation– Electrically tunable Fabry-Perot Bragg grating for signal processing– Fully reconfigurable waveguide Bragg grating for programmable

photonic signal processing– Electrically programmable equivalent-phase-shifted waveguide Bragg

grating for multichannel signal processingConclusion

Outline

6

OFC2019Chirped RF waveform generation

Autocorrelation(Matched Filtering)

Autocorrelation(Matched Filtering)

Chirp-free pulse

Chirped pulse

Chirped microwave pulse can be compressed by matched filtering, widely employed in Radar systems.

-1500 0 15000

1

Time (ps)

Norm

. Apm

.

-500 0 500-1

0

1

-500 0 500-1

0

1

Time (ps)

Norm

. Apm

.

7

OFC2019Photonic microwave waveform generation based on spectral shaping and frequency-to-time mapping

8

OFC2019

• Frequency-to-time mapping

Wavelength-to-time mapping, namely dispersive Fourier transformation, is a fast and effective way to measure optical spectrum in the time domain.

Dispersive Elementt

ω

t( )g t

( )y t

( )G ω

( ) tGω

ω=Φ

≈

Photonic microwave waveform generation based on spectral shaping and frequency-to-time mapping

9

OFC2019

λ

Input Output

FSR = 1 / τ

Offset waveguideLCBG1

LCBG2

λ

τ

On-chip spectral shaper incorporating linearly chirped waveguide Bragg gratings

10

OFC2019On-chip spectral shaper incorporating linearly chirped waveguide Bragg gratings

Perspective view of the proposed on-chip silicon-basedoptical spectral shaper. (Inset: (Left) Wire waveguide and(Right) Rib waveguide)

λ

λSIlicaSIlicon

SiO2

W

Si

SiO2

H1SiH2

SiO2

SiW

Si

SiO2

H

W. Zhang and J. P. Yao, J. Lightw. Technol. 33, 5047-5054 (2015).

(a) Schematic layout of the designed on-chip spectralshaper; (b) Image of the fabricated spectral shapercaptured by a microscope camera.

(b)

Input Grating Coupler

Adiabatic S- Bend

Linearly Chirped Grating

Output Grating Coupler Compact

Y-Branch

Taper I Taper II

Offset Waveguide

linearly Chirped Grating

(a)

11

OFC2019

SIlicaSIlicon

1.60

1.75

1.90

-20

-10

0

Refle

ctio

n (d

B)

Grou

p De

lay

(ns)

-20

-10

0

1.50

1.65

1.80

1.53 1.545 1.56Wavelength (um)

1.60

1.75

1.90

-20

-10

0

(a)

(b)

(c)

Perspective view of the proposed LC-WBG. (Inset: Simulatedfundamental TE mode profile of the rib waveguide with the ribwidth of 500 nm (left) and 650 nm (right)).

Measured spectral and group delayresponses of the LC-WBG with the ribwidth increasing from 500 nm to (a) 550nm, (b) 600 nm and (c) 650 nm alongthe gratings.

On-chip spectral shaper incorporating linearly chirped waveguide Bragg gratings

2B effnλ = Λ

12

OFC2019Experimental Results

1.53 1.538 1.546

-50

-35

-20

Wavelength (um)

Pow

er (d

Bm)

1.53 1.538 1.546-50

-35

-20

Wavelength (um)

OSC

ISOOn-Chip

Spectral ShaperPD

EDFA

TMLLED

FA

PCDCF

Experimental setup. TMML: tunable mode lock laser. ISO: Isolator; EDFA: erbium-doped fiberamplifier. PC: polarization controller. DCF: dispersion compensation fiber. PD: photodetector.OSC: oscilloscope.

Measured spectral response of anon-chip spectral shaper when thelength of the offset waveguide is(left) zero and (right) the length ofthe LC-WBG.

13

OFC2019Experimental Results

-400 -200 0 200 4000

0.5

1

Time (ps)

Nor

mal

ized

Ampl

itude

4 10 160

1

2

Ampl

itude

(mA)

Time (ns)

Time (ns)

Inst

anta

neou

s Fr

eque

ncy

(GHz

)

4 10 16

15

30

00.1

0.5

0.9

(c)

(a)

(b)

Experimental result: (a) the generated LCMW; (b) experimentalspectrogram curve and numerical instantaneous frequency of thegenerated LCMW, and (c) compressed pulse by autocorrelation whenthe length of the offset waveguide equates to zero.

-400 -200 0 200 4000

1

Time (ps)

0.5

Nor

mal

ized

Ampl

itude

5 15 25 350.2

0.8

1.4

Ampl

itude

(mA)

Time (ns)

Time (ns)5 15 25 35

10

20

30

Inst

anta

neou

s Fr

eque

ncy

(GHz

)

0.1

0.5

0.9

(a)

(b)

(c)

Experimental result: (a) the generated LCMW; (b) experimentalspectrogram curve and numerical instantaneous frequency of thegenerated LCMW, and (c) compressed pulse by autocorrelation whenthe length of the offset waveguide equates to the length of LC-WBG.

14

OFC2019

Photonic Integrated Circuits - Material Systems Silicon photonic gratings– Chirped Bragg gratings for RF generation– Phase-shifted gratings for temporal differentiation– Electrically tunable Fabry–Perot Bragg grating for signal processing– Fully reconfigurable waveguide Bragg grating for programmable

photonic signal processing– Electrically programmable equivalent-phase-shifted waveguide Bragg

grating for multichannel signal processingConclusion

Outline

15

OFC2019Photonic temporal differentiator

The transfer function:

1556.5 1557 1557.5 15580

0.2

0.4

0.6

0.8

1

Wavelength (nm)

Mag

nitu

de

(a)

π

1556.5 1557 1557.5 1558-4

-3.5

-3

-2.5

-2

-1.5

-1

Wavelength (nm)

Phas

e (

rad)

(b)

Magnitude and phase response of a differentiator.

( ) ( )n

n

d x ty t

dt=A nth order temporal differentiator:

Applications: phase to intensity conversion in an optical phase-modulated system.

16

OFC2019

(b)

(c) (d)

Phase-shifted Grating on Ridge Waveguide

Taper Waveguide

(a)

Strip WaveguideGrating Coupler

Input Grating coupler

Phase-Shifted Bragg Grating

Output Grating coupler

Taper Taper

W. Zhang, W. Li, and J. P. Yao, IEEE Photon. Technol. Lett. 26, 2383-2386 (2014).

Configuration of the phase-shifted Bragg grating (PSBG) in a silicon-on-insulator ridge waveguide.

(a) Schematic layout. (b) Image of the fabricateddevice. (c) Image of the grating couplers and the stripwaveguides. (d) Image of the taper waveguides for thetransition between the strip waveguides and ridgewaveguides.

Photonic microwave temporal differentiator using an integrated phase-shifted Bragg grating

17

OFC2019

1556.5 1558.1

-50

-46

-42

-38

-34

wavelength (nm)

Pow

er (d

Bm)

ReflectionTransmission

1557.3 1556.8 1557.1 1557.40

0.5

1

wavelength (nm)

Refle

ctio

n (a

.u.)

-1

0

1

2

Phas

e (r

ad)

-2

0.3 nm

(Left) Measured reflection and transmission spectral responses of the fabricated PSBGon a ridge waveguide with a designed corrugation width of 125 nm. (Right) Zoom-inview of the reflection notch and its phase response.

Experimental Results

18

OFC2019

(Left) An input Gaussian pulse with an FWHM of 25 ps, and (Right)the temporally differentiated pulses by simulation and experiment.

MLL

Wave-Shaper Polarizor PD

OSCPhase-Shifted Bragg

Grating on SOI

PCEDFA EDFA

Experimental setup. MML: mode lock laser. EDFA: erbium-doped fiber amplifier. PC: polarization controller. PD: photodetector. OSC: oscilloscope.

Experimental Results

19

OFC2019

Photonic Integrated Circuits - Material Systems Silicon photonic gratings– Chirped Bragg gratings for RF generation– Phase-shifted gratings for temporal differentiation– Electrically tunable Fabry–Perot Bragg grating for signal processing– Fully reconfigurable waveguide Bragg grating for programmable

photonic signal processing– Electrically programmable equivalent-phase-shifted waveguide Bragg

grating for multichannel signal processingConclusion

Outline

20

OFC2019

W. Zhang, N. Ehteshami, W. Liu, and J. Yao, Opt. Lett. 40, 3153–3156 (2015)

21

OFC2019Silicon-based on-chip electrically tunable phase-shifted waveguide Bragg grating

1540.5 1541.5 1542.5

-40

-30

-20

Wavelength (nm)

Pow

er (d

Bm)

ReflectionTransmission

ReflectionTransmission

1540.5 1541.5 1542.5

-40

-30

-20

Wavelength (nm)

Pow

er (d

Bm)

ReflectionTransmission

Measured spectra when a zero bias voltage is applied. Thenotch in the reflection band has a 3-dB bandwidth of 46pm with a Q-factor of 33,500, and an extinction ratio of16.4 dB.

22

OFC2019Silicon-based on-chip electrically tunable phase-shifted waveguide Bragg grating

1540.5 1541.5 1542.5

-40

-30

-20

Wavelength (nm)

Pow

er (d

Bm)

V=-0V=-0.8V=-0.85V=-0.88V=-0.9V=-0.92

V=-0.95V=-0.95

V=-0V=-0.8V=-0.85V=-0.88V=-0.9V=-0.92

V=-0.95V=-0.95

1540.5 1541.5 1542.5-40

-30

-20

Wavelength (nm)

Pow

er (d

Bm)

1541.6 1541.9-40

-30

-20

V=0V=3.5V=8V=13V=16

Reverse Bias

Forward Bias

Blue-shift of the transmission spectrum when the PN junction is forward biased.

Red-shift of the transmission spectrum when the PN junction is reverse biased.

23

OFC2019Silicon-based on-chip electrically tunable phase-shifted waveguide Bragg grating

The resonance wavelength is shifted. A fixedresonance wavelength with a tunable phase-shift isdesired.

By incorporating multi-phase-shifted blocks in thePS-WBG, a delay line with a wider bandwidthcould be realized .

Application 1: Tunable fractional-order photonic temporal differentiator

Application 2: Tunable optical delay line

24

OFC2019

Photonic Integrated Circuits - Material Systems Silicon photonic gratings– Chirped Bragg gratings for RF generation– Phase-shifted gratings for temporal differentiation– Electrically tunable Fabry–Perot Bragg grating for signal processing– Fully reconfigurable waveguide Bragg grating for programmable

photonic signal processing– Electrically programmable equivalent-phase-shifted waveguide Bragg

grating for multichannel signal processingConclusion

Outline

25

OFC2019

W. Zhang and J. P. Yao, Nature Comm., 9, 1396 (2018)

26

OFC2019

Wafer Grating Doping Independent Electrodes

Voltage Control

Programmable grating

Grating design

n1

n2

V1 V2 V3 V4 V5 V6 V7

n1

n2

V1 V2 V3 V4 V5 V6 V7

n1

n2

V1 V2 V3 V4 V5 V6 V7

27

OFC2019Grating design

28

OFC2019Measured reflection and transmissionspectrums.

(a) Reflection and transmission spectrum ofthe fabricated grating in the static state;(b) Notch wavelength shift when the biasvoltages applied to the left and right sub-gratings vary synchronously;(c) Extinction ratio tuning while the notchwavelength is kept unchanged;(d) Reflection and transmission spectrumswhen the grating is reconfigured to be auniform grating;(e) Wavelength tuning of the uniform grating;(f) Reflection and transmission spectrumswhen the device is reconfigured to be auniform grating by increasing the cavity loss;(g) Reflection and transmission spectrumswhen the device is reconfigured to be twoindependent uniform sub-gratings; and(h) Reflection and transmission spectrumswhen the device is reconfigured to be achirped grating.

29

OFC2019Programmable microwave signal processor

RF Input

PDPC1PC2

Silicon substrate

10100...

DC SourcesMZM

Power Meter

EDFATLS

RF Input

PDPC1PC2

Silicon substrate

10100...

DC SourcesMZM

Power Meter

EDFATLS

The experimental set-up consists of a tunable laser source (TLS), a polarization controller (PC), aMach-Zehnder modulator (MZM), an erbium-doped fiber amplifier (EDFA) and a photodetector (PD).

30

OFC2019Experimental demonstration

W. Zhang and J. P. Yao, Nature Comm. 9, 1396 (2018)

0 1000 20000

0.5

1Po

wer

(dBm

)

Time (ps)

n = 0.143

0 1000 20000

0.5

1

Pow

er (d

Bm)

Time (ps)

0

0.5

1

Pow

er (d

Bm)

0

0.5

1

Pow

er (d

Bm)

b c

e

-4 -2 +2 +4-0.8

-0.4

0

0.4

0.8

0Frequency (GHz)

Phas

e (r

ad)

1.7

-0.825

-2.06

V1 V2 V3+200

0 0 0+20 0 -0.825+20 0

-2.30 +11+20

V

0 -2.63 0

a

-4 -2 +2 +4-0.8

-0.4

0

0.4

0.8

0Frequency (GHz)

Phas

e (r

ad)

1.7

-0.825

-2.06

V1 V2 V3+200

0 0 0+20 0 -0.825+20 0

-2.30 +11+20

V

0 -2.63 0

a

0 1000 2000Time (ps)

n = 0.229d

0 1000 2000Time (ps)

n = 0.541

Function 1: Photonic temporal differentiation Function 2: Microwave time delay

Function 3: Microwave frequency identification

31

OFC2019

Photonic Integrated Circuits - Material Systems Silicon photonic gratings– Chirped Bragg gratings for RF generation– Phase-shifted gratings for temporal differentiation– Electrically tunable Fabry-Perot Bragg grating for signal processing– Fully reconfigurable waveguide Bragg grating for programmable

photonic signal processing– Electrically programmable equivalent-phase-shifted waveguide Bragg

grating for multichannel signal processingConclusion

Outline

32

OFC2019Equivalent-phase-shifted Bragg grating

Conventional phase-shifted waveguide Bragg grating

grating pitch phase-shifted block

Equivalent-phase-shifted (EPS) waveguide Bragg grating

Uniform grating

Sampling function

EPS grating

P+∆Psampling period P

Feature size three orders of magnitude larger easy to fabricate

33

OFC2019Programmable EPS grating design

W. Zhang and J. P. Yao, J. Lightw. Technol., 37, 314-322 (2019).

34

OFC2019Programmable EPS grating design

Wafer Grating Doping Independent Electrodes

Voltage Control

Programmable EPS Grating

35

OFC2019Programmable EPS grating design

36

OFC2019Performance 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

37

OFC2019Performance evaluation：independent test

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

38

OFC2019Performance evaluation: programmability

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

39

OFC2019Multichannel 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 isexperimentally demonstrated. The figure shows the measured temporallydifferentiated pulses corresponding to a differentiation 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

40

OFC2019

Thank you

Silicon photonics is a solution for ultra-fast optical signal processing withreduce the size and cost.

By electrical tuning, a silicon photonic grating can be made programmableand reconfigurable for various optical or microwave signal processing

Heterogeneous integration may be needed to produce laser sources andoptical amplifiers using III-V materials, to achieve monolithic photonicintegrated signal processing systems (system on chip) - a key challenge forwide applications of silicon photonics.

Conclusion

41

OFC2019Acknowledgments

CMC Microsystems

NSERC Si-EPIC program