Photonic Devices
(The control of…)
Andrea Melloni
F. Morichetti, S. Grillanda, D. Melati, N. Peserico, M. Carminati,
A. Annoni, P. Ciccarella, G. Ferrari, M. Sampietro, M. Sorel
Politecnico di Milano, Italy
A. Melloni, Progress in photonics, Firenze 2015
http://photonics.deib.polimi.it
Politecnico di Milano (Italy) - Photonic Devices Lab
http://photonics.deib.polimi.it
400 m2
A. Melloni, Progress in photonics, Firenze 2015
1969: 46 years of integrated optics …
A. Melloni, Progress in photonics, Firenze 2015
3
Integrated photonics: ubiquitousness and complexity
A. Melloni, Progress in photonics, Firenze 2015
4
Market: 350 B€ (650 B€ in 2020)
http://www.photonics21.org/download/Brochures/Photonics_Roadmap_final_lowres.pdf
A. Melloni, Progress in photonics, Firenze 2015
5
Technologies and Waveguides
Ge:SiO2
0.5…3 %
SiON
2…8 %
Si3N4
38 %
InP
3 / 70 %
As2S3
60…100 %
SOI
140%
Dn
Mach-Zehnder
D. Couplers, Y, MMI, Star couplers
Ring Resonators
Gratings
A. Melloni, Progress in photonics, Firenze 2015
6
Waveguides
2.2 mm
2.2 mm
Silicon Nitride
<0.3 mm
BPSG
2-5 mm
SiON
Silicon (SOI)
HSQ / SiO2
220 nm
Silicon Oxynitride
Si
SiN
SiO2
480 nm
SiO2
Photonic crystal wg
Segmented waveguide
A. Melloni, Progress in photonics, Firenze 2015
SiO2
Waveguide for sensing
Dielectric (SiO2…SiON…Si3N4, polymers)
Beam forming network
Arrayed Waveguide grating
A. Melloni, Progress in photonics, Firenze 2015
8
Indium Phosphide
Courtesy of TU/e
A. Melloni, Progress in photonics, Firenze 2015
9
Silicon photonics
Slow light, trap light
CMOS silicon modulators
Filter
Delay lines
A. Melloni, Progress in photonics, Firenze 2015
Resonant Router
Biochip
10
Indium Phosphide
The (potential) market forecast
[M$]
JePPIX Roadmap
Using Generic Integrated
Photonics
2012
800
700
600
500
400
300
200
100
0
Silicon Photonics
*
*
*
*
*
2013 ------------------------------------------------- 2024
A. Melloni, Progress in photonics, Firenze 2015
11
A Moore law for photonics (?)
M. Smit et al., “An introduction to InP-based generic integration technology”, 2014 Semicond. Sci. Technol.
T. Baehr-Jones et al., “Myths and rumours of silicon photonics,” Nat. Photonics, vol. 6, Apr. 2012.
A. Melloni, Progress in photonics, Firenze 2015
12
It’s a long way (in my view) …
• Moore law in photonics… No scaling in photonics !
• Photonics as electronics…. Photonics is analog !
• Plasmonic, graphene, carbon nanotubes …
• CMOS compatibility… Mendeleev on chip !
• More Moore or More than Moore? … Integration, synergy
• Everyone does their job! … generic foundry scheme
• Control & feedback, toward “system-on-a-chip” paradigm
A. Melloni, Progress in photonics, Firenze 2015
13
Control & Feedback: motivations

Benefits of photonic integration lies in
the aggregation of several components

Technology can squeeze many devices
in small chips
MINIATURIZATION
INTEGRATION
MIT

Complex photonic systems-on-chip
are still struggling to emerge...
A. Melloni, Progress in photonics, Firenze 2015
14
Control & Feedback: motivations

Benefits of photonic integration lies in
the aggregation of several components

Technology can squeeze many devices
in small chips
Technology is critical…
High Index contrast technologies
ΔT = 1 K → Δf = 10 GHz
MINIATURIZATION
Δn = 10-4 → Δf = 10 GHz
Δw = 1 nm → Δf = 100 GHz
TE/TM and λ dependence…
INTEGRATION
MIT

Complex photonic systems-on-chip
are still struggling to emerge...
A. Melloni, Progress in photonics, Firenze 2015
(Interferometric) devices suffer from
temperature drifts, xtalk, fabrication
tolerances, nonlinearities, aging…
15
Control & Feedback: motivations

Benefits of photonic integration lies in the
aggregation of several components

Technology can squeeze many devices
in small chips
Technology is critical
Silicon Photonics:
ΔT = 1 K → Δf = 10 GHz
Δn = 10-4 → Δf = 10 GHz
MINIATURIZATION
Δw = 1 nm → Δf = 100 GHz
TE/TM and λ dependent
≠
INTEGRATION
Complex photonic systems-on-chip are
still struggling to emerge...
Toward a “LESS” world
FormatLESS
ContentsLESS
A. Melloni, Progress in photonics, Firenze 2015
Less costs
Less Latency

DirectionLESS
Less space
Less energy
GridLESS
MIT
ColorLESS
(Interferometric) devices suffer from
temperature drifts, xtalk, fabrication
tolerances, nonlinearities, aging…
16
Definition of “System”
Supervisory
Inputs
Control &
Calibration
working point
estimation
actuation
command
Sensors
Actuators
physical
effect
A. Melloni, Progress in photonics, Firenze 2015
physical
effect
17
Definition of “System”
Supervisory
Inputs
Control &
Calibration
Feedback…
working point
estimation
actuation
command
Sensors
Actuators
physical
effect
physical
effect
Photonics needs feedback and control
A. Melloni, Progress in photonics, Firenze 2015
18
Heater: “The” actuator
Au+NiCr+Ti
SiO2
Silicon
Length
1-3 mm
10-50 mm
p shift
300-400 mW
10-20 mW
Dneff / DT
110-5 °C-1
210-4 °C-1
Response time
1 ms
10 ms
Crosstalk
high
low
A. Melloni, Progress in photonics, Firenze 2015
S. Zanotto, Laser Photonics Rev., 2015
19
(Non Perturbative)
Probes
Monitor to detect light level in waveguides
and provide feedback (test pin)
Hitless (transparent), small, low power…
A. Melloni, Progress in photonics, Firenze 2015
20
Light-waveguide interaction
 Surface State Absorption
 Surface states are located
typically within the first two/three
silicon atomic layers (≈ 1 nm)
Interface
 Intra-gap energy states create a
free carrier and a corresponding
recombination center
SSA process
Band bending
Conduction band
Energy
hn
hn
Traps
Valence band
Si
SiO2
A. Melloni, Progress in photonics, Firenze 2015
S. Grillanda, F. Morichetti, Nature Comm., Sept. 2015 21
The CLIPP concept
ContacLess Integrated Photonic Probe (CLIPP)
metal
1 mm
SiO2
metal
L
CA
Metal
DG
CA
Si
Light
in
SiO2
Contactless capacitive
access to the waveguide
SiO2
Light
out
longitudinal view
Si
SiO2
100 nm
Measuring the SSA
induced waveguide
conductance change DG
through an
ultrasensitive electric
detection circuit
Light dependent conductance variation
Si conductivity change
A
induced by light
Carrier mobility is typically
L
lower on the surface
DNs
compared to the bulk
A. Melloni, Progress in photonics, Firenze 2015
ms
Free carriers
generated on the
surface by SSA
Si waveguide cross section
CLIPP length
surface free-carrier density
carrier mobility
22
The CLIPP concept
ContacLess Integrated Photonic Probe (CLIPP)
1 mm
SiO2
metal
L
CA
Metal
DG
CA
Si
SiO2
Light
out
Light
in
SiO2
longitudinal view
Si
SiO2
100 nm
Ve ~ 1V
fe ~ 1MHz
Measuring the SSA
induced waveguide
conductance change DG
through an
ultrasensitive electric
detection circuit
90°
100 kW
V, f0
ie
Re[Ywg]
+
Transimpedance
Amplifier (TIA)
Patented
metal
Contactless capacitive
access to the waveguide
Im[Ywg]
Lock-In Amplifier
A. Melloni, Progress in photonics, Firenze 2015
“Silicon Photonics: Stalking Light,”
23
Nature Photonics 8, 266 (2014)
CLIPP performance
CLIPP concept demonstrated for:
Top view of the CLIPP
100 mm
Waveguide
Wire
bonding
pads
2
CLIPP
electrodes
L
- single mode/multimode wgs
- compact size (L down to 25 mm)
- TE/TM polarizations
- sensitivity down to -30 dBm
- 40 dB dynamic range
- speed > 20 ms (limited by TIA noise)
2
10
Ve = 1V
fe = 1 MHz
Conductance variation DG [nS]
Conductance variation DG [nS]
10
L = 100 mm
1
10
w = 480 nm
0
10
w = 1 mm
-1
10
-30
-20
-10
0
Local power P [dBm]
A. Melloni, Progress in photonics, Firenze 2015
10
TE
TM
L = 100 mm
1
10
0
10
-1
10
-25
-20
Ve = 1 V
fe = 1 MHZ
-15
-10
Local power [dBm]
-5
0
24
Multipoint on-chip monitoring
Through
Light
In
Thermal
Actuator
CLIPP 3
CLIPP 2
To
OSA
CLIPP 1
100 µm
-50
0.8
0.7
-100
0.6
-150
CLIPP 2
0.5
0.4
-200
0.3
-250
1555.8
1555.9
1556.0
Wavelength [nm]
A. Melloni, Progress in photonics, Firenze 2015
0.2
250
2.0
0.9
0.8
200
0.7
0.6
150
100
0.5
0.4
0.3
50
0.2
Estimated Optical Power [mW]
0.9
Inside
1.0
Optical Transmission
OSA
Drop
1.0
Electrical Signal Variation [ppm]
Through
port
Through
Optical Transmission
Electrical Signal Variation [ppm]
0
1.5
1.0
0.5
0.1
0
0.0
1555.8
1555.9
1556.0
Wavelength [nm]
0.0
1555.8
1555.9
Wavelength
25
Multipoint on-chip monitoring
Through
Light
In
Thermal
Actuator
CLIPP 3
CLIPP 2
To
OSA
CLIPP 1
100 µm
200
0.7
150
100
0.6
CLIPP 2
0.5
0.4
50
0.3
0.8
200
0.7
0.6
150
0.5
0.4
100
0.3
0.2
50
0.1
0.8
1.5
0.5
0.4
0.3
0.5
2.0
CLIPP 3 1.5
0.7
0.6
1.0
Inside
Estimated Optical Power [mW]
0.8
0.2
Optical Transmission
0.4
-200
0.3
250
0.9
Estimated Optical Power [mW]
-150
0.5
0.9
Inside the
cavity
Inside
Drop
1.0
2.0
0.9
Optical Transmission
0.6
1.0
Electrical Signal Variation [ppm]
0.7
-100
Drop
1.0
OSA 250
Electrical Signal Variation [ppm]
0.9
-50
0.8
Optical Transmission
Electrical Signal Variation [ppm]
1.0
0
Optical Transmission
Through
port
Through
Through
1.0
0.5
0.1
0.2
-250
0.2
0.0
0.0
0
0.0
0
0.0
1555.9
1556.0 1555.8
1555.9
1555.8 1556.0
1555.9
1556.0 1555.8
1555.9
1555.81556.0
1555.9
1556.0 1555.8
1555.9
Wavelength [nm]
Wavelength [nm]
Wavelength [nm]
Wavelength
Wavelength [nm]
Wavelength [nm]
A. Melloni, Progress in photonics, Firenze 2015
26
Control Layer:
applications
A. Melloni, Progress in photonics, Firenze 2015
27
Integral
controller
Vd
fd
Vh
In
ε
Heater
ie
Lock-in detector
CLIPP
80 µm
CLIPP readout (fe)
Ve
Out
Error signal ε [µV]
Dithering
Intra-cavity
Optical intensity
Wavelength Locking (dithering approach)
1
Ve = 1 V
fe = 1 MHz
0.5
fd = 160 Hz
0
-100
-50
0
50
Wavelength detuning [pm]
300
Vd = 100 mV
(0.14 K)
0
-300
-100
-50
0
50
Wavelength detuning [pm]
Optical intensity
1
FEEDBACK LOOP ON
Response to a 50 pm (= ring bandwidth) detuning
0.5
Wavelength locking in 150 ms
Loop response can be speeded up with
FEEDBACK LOOP OFF
0
0
0.2
0.4
0.6
0.8
1
Time [s]
A. Melloni, Progress in photonics, Firenze 2015
100
 faster CLIPP response
 optimized control laws (P, PI)
100
Wavelength monitoring
CLIPP
demodulation
Two input channels at different wavelengths
λ2 λ
λ1 = 1549.59 nm
Heater
voltage
1
λ2 = λ1 + 120 pm
Heater
CLIPP demod. @ fe
λ2 λ1
?
?
CLIPP signal
V, f0
CLIPP demod. @ fe
1
0.5
Heater
?
0
0
1
2
3
4
5
6
Heater power [mW]
No signal discrimination
A. Melloni, Progress in photonics, Firenze 2015
29
Wavelength monitoring
CLIPP
demodulation
The channels are labeled with a weak
λ2 λ
modulation tone (depth 2%):
Heater
voltage
1
f1 = 10 kHz @ λ1 = 1549.59 nm
f2 = 11 kHz @ λ2 = λ1 + 120 pm
Heater
V, f0
The CLIPP discriminates and monitors
simultaneosuly different channels
resonating in the microring!
1
CLIPP demod.
@ fe + f1
λ1
0.5
λ2
CLIPP signal
λ2 λ1
CLIPP demod. @ fe
0
0
1
1
0
λ1
3
4
5
6
5
6
CLIPP @ fe + f1
0.5
Heater
2
0
1
2
3
4
Heater power [mW]
automatic tuning and locking on l1
A. Melloni, Progress in photonics, Firenze 2015
30
Wavelength swapping
CLIPP
demodulation
The channels are labeled with a weak
λ2 λ
modulation tone (depth 2%):
Heater
voltage
1
f1 = 10 kHz @ λ1 = 1549.59 nm
f2 = 11 kHz @ λ2 = λ1 + 120 pm
Heater
V, f0
The CLIPP discriminates and monitors
simultaneosuly different channels
resonating in the microring!
1
CLIPP demod.
@ fe + f2
λ2
0.5
0
0
1
λ1
SWAP !
Heater
λ2
automatic tuning and locking on l2
A. Melloni, Progress in photonics, Firenze 2015
1
2
3
4
5
6
CLIPP @ fe + f1
0.5
CLIPP signal
λ2 λ1
CLIPP demod. @ fe
0
0
1
1
2
3
4
5
6
3
4
5
6
0.5 CLIPP @ fe + f2
0
0
1
2
Heater power [mW]
31
Multichannel feedback control
Motherboard
Photonic
chip
ASIC
Photonic
chip
ASIC
Motherboard
Motherboard:
• generate the CLIPPs driving signal Ve (fast DAC);
• provide the I/Q clock signals to the lock-ins in the ASIC;
• drive the heaters integrated onto the photonic chip (slow DACs);
• FPGA-based digital processing ;
controlProgress
of up in
tophotonics,
16 independent
feedback control-loops;
A.•Melloni,
Firenze 2015
32
32
Lightpath tracking and feedback control routing
Stage A
Stage B
A. Melloni et al, IPR Conference, July 2015
Stage C
I1
O1
I2
O2
I3
I4
O3
O4
I5
O5
I6
O6
I7
I8
O7
O8
Ai
Bi
Ci
2 x 12 CLIPPs
12 heaters
MZI switch
CLIPP
O7
Vh
Controller
A. Melloni, Progress in photonics, Firenze 2015
PHOTONI C
CHI P
Set point
+
-
CLIPP
signals
O8
33
Routing with pilot tones
I6
I7
1545.5 nm (Ch A)
1558.26 nm (Ch B)
I8
Pilot tones
50 mV (3% modulation)
10
-6
10
-8
-10
-22
10
10
-20
-18
-16
MOD
MOD
Ve=1V,
613 KHz
10 KHz
Out 6 – Ch. B
Ch B
Ch B + tone
-6
-8
-10
-16
1.0
0.8
0.6
0.4
0.2
0.0
-4
10 0
1.0
0.8
0.6
-6
0.4
10
0.2
0.0
0
-8
-16
10
-20
-24
-28
-32-10
-36
10
-40
0
-22
BER
10
Ch A
Ch A + tone
-4
-15
O5
O6
C6
PD [dBm]
BER
10
10
C5
MOD
7 KHz
Out 6 – Ch. A
BER
10
-4
C
-14
A. Melloni, Power
Progress
in photonics, Firenze 2015
[dBm]
Power [dBm]
-13
C7
O7
C8
O8
Pilot tone OFF
Pilot tone ON
Out 8 – Ch. A
2
4
6
10 8
-4
Ch A
Ch A + tone
10
2
4
6
BER
10G CISCO XFP modules
CLIPP Signal CLIPP Signal
I5
B
MOD
10
2
-20
4
-18
Power [dBm]
6
Out 8 – Ch. B
10
12
Ch B
C8
Ch B + tone
C7
C6
C5
-6
8
10
B8
B7
A8
A7
10
12
-8
O8
O7
O6
-10
8
-16
-16
Time [s]
10
-15
12
-14
Power [dBm]
-13
Routing with pilot tones
10G CISCO XFP modules
I6
I7
1545.5 nm (Ch A)
1558.26 nm (Ch B)
I8
Pilot tones
50 mV (3% modulation)
10
10
Ch A
Ch A + tone
-6
10
-8
-10
-22
10
10
-20
-18
-16
-4
C6
MOD
MOD
Ve=1V,
613 KHz
Out 6 – Ch. B
10
Ch B
Ch B + tone
-6
10
-8
-10
-16
10
10
-15
-14
A. Melloni, Power
Progress
in photonics, Firenze 2015
[dBm]
Power [dBm]
-13
O5
O6
C7
O7
C8
O8
Pilot tone OFF
Pilot tone ON
10 KHz
BER
BER
10
10
C5
MOD
7 KHz
Out 6 – Ch. A
BER
10
-4
C
-4
Out 8 – Ch. A
10
Ch A
Ch A + tone
-6
10
BER
I5
B
MOD
-8
-10
-22
10
10
-20
-18
Power [dBm]
-16
-4
Out 8 – Ch. B
Ch B
Ch B + tone
-6
-8
-10
-16
-15
-14
Power [dBm]
-13
Hitless monitoring of 4x10 Gb/s WDM-MDM channels
f3
f1
λ1=1544.2 nm
l 1,TE l 1,TM l 2,TE l 2,TM
90°
Si photonic chip
50%
50%
l 1,TE
CLIPP
Decorrelation
fiber coil
f4
f2
Ve
-5
10
-6
-6
10
10
λ1,TE
BER
-6
10
-6
10
-7
λ1,TM
λ2,TE
-7
10
-7
10
λ2,TM
-7
10
10
-8
-8
10
-8
10
-20
Channel monitoring OFF
-5
10
10
l 2,TM
Channel monitoring ON
-5
-5
10
l 2,TE
BER-T
ie
CLIPP readout
and pilot tones
demodulation
Pilot tones f1, f2, f3, f4
PBS
DEMUX
λ2=1558.8 nm
10 Gbit/s
OOK
l 1,TM
-9
-8
-15
10
-10 -20
10
-15
A. Melloni, Progress in photonics, Firenze 2015
10
-25
-10
-9
-20
Receiver power [dBm]
10
-15 -25
-20
-15
36
Conclusions, the keywords
PROBE
FEEDBACK
A. Melloni, Progress in photonics, Firenze 2015
TUNING
More than Moore
Adaptive
Generic
Foundry
Programming
37
Acknowledgments
We acknowledge financial support from:
Eu Project – ICT/FET (2013-2016)
Breaking the barriers of Optical Integration
www.bboi.eu
Italian National Research Project SAPPHIRE
Shared Access Platform to PHotonic Integrated Resources
We are grateful to:
Prof. Marc Sorel & Dr. Michael J. Strain
James Watt Nanofabrication Center at University of Glasgow
for support in the fabrication of the silicon photonic devices
A. Melloni, Progress in photonics, Firenze 2015