Optoelectronics GroupElectronics Department

University of Pavia

Operating Regimes And Modelling Of Single Mode Monolithic Semiconductor Ring Lasers

G. Giuliani, R. Miglierina, S. Donati, University of Pavia, ItalyM. Sorel, P. J. R. Laybourn, University of Glasgow, UK

A. Sciré, IMEDEA, Palma de Mallorca, Spain

Semiconductor Ring Laser(SRL)

MOTIVATION

Easy integration devices (no mirrors or Bragg gratings are required)

Possible applications:

Gyroscopy, Filters, Wavelength Converters, MUX/DEMUX

Application in OEICs (Opto-Electronic Integrated Circuits):

Optical Gating, Optical Memories

SRL Structure

R

L

PD1 PD2

PD3

MODE 2

MODE 1

MATERIAL: AlGaAs/GaAs

InP/InGaAsP

RING RADIUS: 1mm

PD1,2 LENGTH: 1mm

PD3 LENGTH: 50-200μm

FABRICATION

LAS = 860nm

Single Longitudinal

Mode

Dynamics:Experimental Results

P-I CHARACTERISATION

BIDIRECTIONAL

CW

BIDIRECTIONAL

HO

B: BIDIRECTIONAL

C: UNIDIRECTIONAL

UNIDIRECTIONAL

Photocurrent PD1

Photocurrent PD2

Frequency: 80-100MHz

Dynamics:Theoretical Model

SLOWLY VARYING AMPLITUDE MEAN FIELD NORMALIZED RATE EQUATIONS

S, C = SELF/CROSS SATURATION COEFFICIENTSEXPLICIT COUPLING BETWEEN THE TWO MODES (H. A. Haus, IEEE JQE,

1985)

KD = DISSIPATIVE COUPLING

KC = CONSERVATIVE COUPLINGIMPORTANT TO UNDERSTAND SRL DYNAMICS

Dynamics:Simulations Results

KD AND KC COEFFICIENTS CAN BE ADJUSTED TO FIT THE MODE OSCILLATION FREQUENCY OBSERVED IN THE EXPERIMENTS

Time [s]

Time [s]

Pow

er

of

the t

wo m

odes

[a.

u.]

Experiment-Model Comparison

S=1ns

P=20ps

S=0.0335

C=0.037

KD=0.00035

KC=0.0079

=3.5

SRL Regimes Interpretation

NEW RESULT IN SEMICONDUCTOR LASERS

KC = LOCALISED REFLECTION IN THE CAVITY

KD = LOCALISED LOSS IN THE CAVITY

IT FAVOURS HARMONIC OSCILLATIONS

IT FAVOURS UNIDIRECTIONALITY

Previous Results

DYE LASER F. C. Cheng, Phys. Rev. A, 1992

GAS LASER R. J. C. Spreew et al., Phys. Rev. A, 1990

HARMONIC OSCILLATION INSTABILITY:

He-Ne LASER: R. J. C. Spreew et al., Phys. Rev. A, 1990

Coherence Length Measurement

Linewidth Measurement:Experimental Setup

Low power coupled in SM fiber (~ 50-100nW)

Contrast Measurement Technique (non-conventional)

Linewidth Measurement:Results

LINEWIDTH ESTIMATION

Linewidth ~ doubling in Bi-HO regime

Bi-CW110 MHz

UNI38 MHz

Mode power halving

21

PFP

Schawlow-Townes limit

Bi-CW UNI

Conclusions

Experimental characterisation of semiconductor ring lasers

(AlGaAs - InGaAsP)

•

SRL theoretical model realisation and computer simulations•

Experiment-Model Fitting• SUCCESSFUL

Linewidth first-time measurement in UNI and Bi-CW regimes (40-100MHz)•

Optical Spectrum Measures

Scale: 21.6 GHz/div

MODE SPACINGMEASUREMENT

13.6 GHz Rn

c

2

SRL Structure

RIDGE STRUCTURE SINGLE TRANSVERSAL MODE

SRL Structure

Linewidth Measurement:Mode Cross-Correlation

Cross-Correlation Measurement

Linewidth Measurement:Mode Cross-Correlation

Interferometric Signal(Oscilloscope Trace)

Cross-Correlation Vs. Autocorrelation