T1 Tutorial description

This tutorial, entitled :

”Visible light communications in smart road infrastructures”,

reports four work areas: Admission Regulation of Traffic to Improve Public

Transport in Urban Areas

Essays for optical communications

Indoor positioning using a-SiCH technology

Connected cars: road to vehicle communication through visible light

II Work Area:

Essays for optical communications

Schematic diagram of the transducers essays. An indoor, line-of-sight visible light communication link.

Optoelectronic WDM system:

Motivation and Objectives

RESEARCH QUESTION : “Which kind of amorphous Si/SiC transducers, should be developed to allow the recovery of specific wavelengths for the transmission over WDM networks, in the visible spectrum, that could compete with conventional detection electronic devices in optical communications industry ?”

System Architecture

Experimental Design

Optoelectronic Algorithm Interface

Applications

MAIN WORK AREAS:

Outline

• Dynamical effects: A two stage active circuit. Optoelectronic simulator.

• Reconfigurable active filters: Opto-electronic conversion. Optoelectronic logic

functions.

• Bias controlled device: Voltage and Optical bias. Self amplification.

Photonic filters.

• Conclusions and future trends.

400 500 600 700 800

0,0

0,1

0,2

0,3

0,4

75 Hz

NC12p-i(a-SiC:H)-n/ITO/p-i(a-Si:H)-n

Ph

oto

cu

rre

nt

(a

)

Wavelength (nm)

-10 V

-5 V

0 V

+3 V

• State of art: Experimental Design Work Area. The original idea.

p-i-n p-i-n

State of art of a-Si/SiC Photodiodes

400 450 500 550 600 650 700 750 8000,00

0,02

0,04

0,06

0,08

0,10

0,12

0,14

0,16

0,18

0,20

#M007192 (2mWcm-2)

#M007192(L=0)

#M006301(L=0)

#M006291(2mWcm-2)

#M006301(2mWcm-2)

#M006291(L=0)

Sen

siti

vit

y (

A/W

)

Wavelength (nm)

Light-to-dark Sensitivity depends strongly on the carbon concentration

-6 -5 -4 -3 -2 -1 0 1 2

-8x10-8

-6x10-8

-4x10-8

-2x10-8

0

a)

S=650 nm

NC#5 (pin/pin)

whithout

optical bias

L=550 nm

L=650 nm

L=450 nm

Photo

curr

ent (A

)

Voltage (V)Green Blue

Color rejections function on the applied bias

P. Louro, M. Fernandes, A. Fantoni, G. Lavareda, C. Nunes de Carvalho, R. Schwarz and M. Vieira “An amorphous SiC/Si image photodetector with voltage-selectable spectral response”Thin Solid Films, 511-512, 2006, pp.167-171

The thickness of the front photodiode was optimized for blue collection and red transmittance The thickness of the back photodiode was adjusted to achieve high collection in the red spectral range

Produced by PECVD

400 500 600 700 800

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35Front cell

ITO/pi´(a-SiC:H)n/ITO/pi(a-Si:H)n/ITO

Pho

tocurr

ent (

a)

Wavelength (nm)

0.0

0.5

1.0

1.5

2.0-5V

+1V

Voltage controlled optical filter

Front diode –Cuts the red

Back diode –Cuts the blue Back cell

400 500 600 700 800

0.0

0.1

0.2

0.3 NC10 p-i'(a-SiC:H)-n-p-i(a-Si:H)-n

75 Hz

Ph

oto

cu

rre

nt (

A)

Wavelength (nm)

-10 V

-5 V

0 V

+3 V

M. Vieira, P. Louro, M. Fernandes, M.A. Vieira, A. Fantoni and M. Barata, “Large area a-SiC:H WDM devices for signal multiplexing and demultiplexing in the visible spectrum”, Thin Solid Films 517 (2009), pp. 6435-6439. Voltage controlled spectral response.

Both front and back diodes act as optical filters confining, respectively, the blue and the red optical carriers, while the green ones are absorbed across both.

0.0 1.0 2.0 3.0 4.0 5.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

V=+1V

V=-8V

G

BR

B (-8V)

R(-8V)

G(-8)

B(+1)

R(+1)

G(+1)

Led R

Led G

Led B

Ph

oto

cu

rre

nt

(A

)

Time (ms)

Front

diode

Back

diode

-

Substrate InOx

p (a-SiC:H)

n (a-SiC:H)

i (a-SiC:H)

200 nm

p (a-SiC:H)

i (a-Si:H)

1000 nm

n (a-SiC:H)

n (a-SiC:H) InOx

B R G

B

R

G

V

Wavelength

Division

Multiplexing

Wavelength

Division

Demultiplexing

Operation Principle

R+G+B R&G&B

soma

+1V

-8V

###

###

###

###

###

###

###

###

###

Experimental Design Work Area

M. Vieira, M. Fernandes, P. Louro, A. Fantoni, M. Barata, M A Vieira, “Multilayered a-SiC:H device for Wavelength-Division (de)Multiplexing applications in the visible spectrum” Mater. Res. Soc. Symp. Proc. Volume 1066 (2008), pp.225-230 DOI:10.1557/PROC-1066-A08-01

Optical

bias

Optical

bias

GL

AS

S

200 nm(a-SiC:H)

Applied Voltage

Channels

B

TC

O

i

1000 nm

(a-Si:H)

p pn n

TC

O

Front diode Back diode

Gi’

G

Optical bias controlled optical filter

400 450 500 550 600 650 7000

20

40

60

80

100

120

140N

orm

aliz

ed

Ph

oto

cu

rre

nt

No background

Red background

Green background

Blue background

Violet background

V=-8V

500 Hz

Ph

oto

cu

rre

nt (n

A)

Wavelength (nm)

N3500

R3500

G3500

B3500

Violtet 3500

0

1

p-i'-n diode

p-i-n diode

B

C

400 450 500 550 600 650 7000

5

10

15

20

25

30

35

40

45

50Back optical bias

No

rma

lize

d P

ho

tocu

rre

nt

V=-8V

500 Hz

Ph

oto

cu

rre

nt

(nA

)

Wavelength (nm)

no bias 500 Hz

R10mA

G10mA

B10mA

V10mA

0

1

2

p-i'-n diodep-i-n diode

B

C

Op

tical b

ias O

ptical b

ias

Dynamics of electrical model with light biasing control

ac equivalent circuit

Two optical gate connections

Q1

Q2 i

n

n

p

i

n

n

p

i

n

n

p

i

n

n

p

i

n

n

p

i

n

n

p

i

n

n

p

i

n

n

p

p

i

n

p

p

i

n

p

p

i

n

p

p

i ’

n

p

p

i

n

p

p

i

n

p

p

i

n

p

p

i

n

p

p

i ’

n

p

I1

I2

I3

I4

M A Vieira, M. Vieira, M. Fernandes, A. Fantoni, P. Louro, M. Barata, Amorphous and Polycrystalline Thin-Film Silicon Science and Technology — 2009, MRS Proceedings Volume 1153, A08-03

Two amplifying elements Two capacitive filter sections

Charge storage modelled by space-charge layer

Two stage active circuit

Light Biasing Control

Electrically programmable

Light triggering

State-space realization of the photonics active filters

State-space

realization of the

equivalent circuit

B

A

C dt

State variables

System matrix

Control matrix Output matrix

Output variables i1,2 Input variables

V1,2

+ +

i

V 1,2

How does the system input affect the state change??

How does the current state affect the state change??

tvR

ti 2,1

2

10

Dyn

am

ics

of

a p

ara

llel b

ucket

co

nn

ec

tio

n

)()(111

11

2,1

2

2

1

1

2,1

222121

11112,1ti

C

Ctv

CRCRCR

CRCR

dt

dv

M. A. Vieira, M. Vieira, J. Costa, P. Louro, M. Fernandes, A. Fantoni, ”Double pin Photodiodes with two Optical Gate Connections for Light Triggering: A capacitive two-phototransistor model” in Sensors & Transducers Journal Vol. 10, Special Issue, February 2011, pp.96-120.

.

/C1

/C2

/R1C1

/R2

dt

/R1C2

/R1C1

dt

/R1C2-1/R2C2

i(t)

+

i2(t)

i1(t) ++

++

+

v1

.

.v2

+

v1

v2

/C1

/C2

/R1C1

/R2

dt dt

/R1C2

/R1C1

dt dt

/R1C2-1/R2C2

i(t)

+

i2(t)

i1(t) ++

++

+

v1

.

.v2

+

v1

v2

Simulator Electrical model Dynamics of electrical model

with light biasing control

Input channels (R G B) Background (R G B) Multiplexed signal

Optoelecronic simulator Vieira, M.A., Louro, P., Vieira, M., Fantoni, A., Steiger-Garção, A. “Light-activated amplification in Si-C tandem devices: A capacitive active filter model “ IEEE SENSORS JOURNAL, VOL. 12, NO. 6, JUNE 2012 pp. 1755-1762 DOI: 10.1109/JSEN.2011.21765372012

Validation of the model

.

Under negative dc

Good agreement between experimental and simulated data

experimental (solid lines)

simulated (symbols)

Without background Encoding: 8-levels

MATLAB as a programming environment and the four order Runge-Kutta

method to solve the state equations

0,0 1,0 2,00

5

10

15

20

25

R

R=0.19

R

B=1.70

R

G=0.42

Red background no background)

IR

IB

IGpi´n

IGpin

IR

IGR

IGB

IB

Ion

I -8V

Ph

oto

cu

rre

nt

(A

)

Time (ms)

0,000 0,001 0,002

0,0

5,0x10-6

1,0x10-5

1,5x10-5

2,0x10-5

2,5x10-5

###

###

=0

=624 nm

###

###

###

###

###

###

0,000 0,001 0,002

B

C

M A Vieira, M. Vieira, M. Fernandes, A. Fantoni, P. Louro, M. Barata, Amorphous and Polycrystalline Thin-Film Silicon Science and Technology — 2009, MRS Proceedings Volume 1153, A08-03

Front Red background Encoding: 4-levels

0,00 0,25 0,50 0,75 1,00 1,250

5

10

15

20=0=624 nm

Photo

curr

ent (

A)

Time (ms)

Rdark

Gdark

Bdark

Red

blue

green

Optical encoded data stream front red/without irradiation

13

0,0 0,5 1,0 1,5 2,0 2,50

10

20

30

40

000

..... tn=n

...........t8=Tt

0=t

R

6000bps

Ph

oto

cu

rren

t (

A)

Time (ms)

D

R

G

B

###

###

###

###

###

###

###

_GB

_G0

_0B

_00

_GB

_0B

_G0

_00

RGB 0GB

R0B 00B

RG0 0G0 R00 000

F

Red Background :

The output waveform becomes a

main 4-level encoding (22).

Without optical bias is an 8-level encoding (23)

to which it corresponds 8 different photocurrent

thresholds.

(αRR<<1)

(αRB>>1)

(αRG<1)

_G0

_0B

_GB

_00

SiC tuneable background nonlinearity-based RGB logic gates

Optical encoded data stream front/back violet irradiation

14

Back violet optical bias :

The output waveform

becomes a main 4-level

encoding (22).

Front violet optical bias

8-level encoding (23) to which it

corresponds 8 different

photocurrent thresholds.

(αVR>>1)

(αVB~1)

(αVG>1)

0,0 0,5 1,0 1,5 2,0 2,50

1

2

3

4

5 Red

Green

Blue

Vpin1

Vpin2

###

###

###

###

pin2

pin1

Photo

curr

ent (a

.u)

Time (ms)

R

R

R

R

0

0

0

0

B B B B

0 0 0 0

0

0

0

0

B

B

B

B

(αVR<<1)

(αVB>>1)

(αVG~1)

G

G

G

G

0

0

0

0

0,0 0,5 1,0 1,5 2,0 2,50,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

V

B pin1

V

B pin2

V

pin2

V

pin1

V

pin2

V

R pin1

Violet background

V

R,G

,B

Time (ms)

10 point AA Smoothing of Data3_B

10 point AA Smoothing of Data3_E

15 point AA Smoothing of Data3_I

15 point AA Smoothing of Data3_C

15 point AA Smoothing of Data3_G

15 point AA Smoothing of Data3_J

SiC tuneable background nonlinearity-based RGB logic gates

Optoelectronic model

Op

tica

l b

ias

Op

tica

l b

ias GL

AS

S

200 nm

(a-SiC:H)

Applied Voltage

Channels

B

TC

O

i

1000 nm

(a-Si:H)

p p n n TC

O

Front diode Back diode

G i’

R

i´ p

n p

n n

i p

Q1

Q2

IB,IG

IR,IG

400 500 600 700 800

0.0

0.1

0.2

0.3 NC10 p-i'(a-SiC:H)-n-p-i(a-Si:H)-n

75 Hz

Ph

oto

cu

rre

nt (

A)

Wavelength (nm)

-10 V

-5 V

0 V

+3 V

400 450 500 550 600 650 7000

1

2

3

4

5

6

7

8 624nm, 3500Hz

624nm, 250Hz

526nm, 3500Hz

526nm, 250Hz

470nm, 3500Hz

470nm, 250Hz

400nm, 3500Hz

400nm, 250Hz

Gain

(

R,

G,

B)

Wavelength (nm)

R3500Hz

R250Hz

G3500Hz

G250Hz

B35000Hz

B250Hz

V250

V3500

Light-activated pi’n/pin a-SiC:H devices that combines the demultiplexing operation with the simultaneous photodetection and self amplification of an optical signal were designed, analyzed, validated and evaluated.

Depending on the applied voltage and wavelength of the external background it acts either as a short- or a long- pass band filter or as a band-stop filter.

Conclusions

Experimental Design

tvR

ti 2,1

2

10

)()(111

11

2,1

2

2

1

1

2,1

222121

11112,1ti

C

Ctv

CRCRCR

CRCR

dt

dv