1

Introduction

For new applications :• fibre-radio systems• optically supplied microwave antennas

There is a need for microwave photonic functions

Emitters Optical switchingmatrixes

Receiversmicrowave microwave

optical fibre optical fibre

2

Axially coupled lasers : fabrication

At IEMN and Tempere University of Technology

Perot-Fabry lasers

Substrate InP SI

Active layer (MQW)

InP p+

GaInAs GaInAs

InP n+

InP p+ InP p+

Substrate InP SI

Active layer (MQW)

InP p+

GaInAs GaInAs

InP n+

Fabrication on semi-insulating substrate Fabrication on N+ substrate

European TMR project

3

f = 11,4 GHz

Axially coupled lasers: microwave experiments

• optical generation of a microwavesignal (beating of the optical modesin a photodetector)• tuning of the frequency withbias currents

• observed on the frequency response

4

The Dual Mode Laser structure

It is a sampled grating DFB laser

Sampled grating structure

P+

N+

elementary sampled grating

10 µm 80 µm

N Contact

P Contact

710 µm long device: - 7 DFB sections (10µm)- 8 FP sections (80 µm)- 2 end DFB sections (40 µm)

It is also a DFB laser with a reduced coupling coefficient

5

Digital Optical Switch

No carrier injection

Carrier injection

BPM Modelling

A Y junction unbalanced by injection of carriers

6

Variation de la puissance du signal hyper à 9GHz en fonction du courant injecté dans le DOS

-120

-100

-80

-60

-40

-20

0

0 5 10 15 20 25 30 35 40

I (mA)

P (

dB

m)

branche éteinte

branche commutée

Département Hyperfréquences & Semiconducteurs

58 dB !

7Département Hyperfréquences & Semiconducteurs

mesure du bruit de phase - modulation 9 GHz

-60

-50

-40

-30

-20

-10

00,00E+00 2,00E+05 4,00E+05 6,00E+05 8,00E+05 1,00E+06 1,20E+06

fréquence relative

P

référence moyenne

commutation moyenne

8

High power photodiodes : possible solutions

1. Travelling-Wave Photodetector– Increased absorption volume– Electrodes = 50 microwave line– Optical and microwave velocity

matching

2. Uni Travelling Carrier Photodiode– Absorption in P+ GaInAs layer (no

field)– Transit of photogenerated electrons

by diffusion (base) and drift (collector)

9

P+ InP

N+ InP

N+ InP

N+ InP

N+ InP

N+ InP

nid GaInAsN+ GaInAsP

N+ GaInAsP

N+ GaInAsP

N+ GaInAsP

N+ GaInAsP

N+ GaInAsP

- Good coupling to the fiber

- One quaternary GaInAsP and

InP layers

- Specific waveguide half lens

New concept : diluted multimode waveguide

1.3 µmor

1.55 µm

10

TM mode, 1.55µmInjection at -7.5µm

Air

Substrate

GaInAs layer

TM mode, 1.55µmInjection at -5µm

Air

Substrate

GaInAs layer

Typical behaviour of the optimized multimode

diluted waveguide

Air

Substrate

Photodetector behaviour

Diluted multimode waveguide : optical behaviour

Vertical scales dilated

11

Experimental results

• Device fabricated at Opto+ (Alcatel)

• 11µm thick epitaxial structure (MOCVD)

• =1.55µm : Max Resp=1.06A/W• =1.30µm : Max Resp=0.86A/W• -1 dB misalign. tolerance = 6.5 µm• Influence of optical polarisation : lower than 0.1dB in all cases • Cut-off frequency > 3GHz @-3V

Work in progress to get millimeter wave devices

• High reliability

0 5 10 15 20 25 30 35 40Bias voltage (V)

10-12

10-11

10-10

10-09

10-08

10-07

10-06

Dar

k cu

rren

t (A

)

After

Before

200°C / -10V / 1030 hours

12

Résultats des transmissions 32-QAM

1km MMFle câble coaxial(référence)

le diagramme

de constellation

le diagramme

de l ’oeil

Département Hyperfréquences & Semiconducteurs

13

Réponses fréquencielles de MMF

fréquence, GHz

rép

on

se,

dB

>80% des fibres intra -bâtiment < 300m

-10

-8

-6

-4

-2

0

2

0 2 4 6 80 2 4 6 8

1km

500m

100m

2

0

-2

-4

-6

-8

-10

Département Hyperfréquences & Semiconducteurs