Optoelectronic Integration of a Resonant Tunneling Diode...

ECIO’08 Eindhoven June 08

Optoelectronic Integration of a Resonant Tunneling Diode and a Laser Diode

B. Romeira, J. M. L. FigueiredoCentro de Electrónica, Optoelectrónica e Telecomunicações,Universidade do Algarve, Gambelas, 8005-139 Faro, Portugal

T. J. Slight, L. Wang, E. Wasige, C. N. IronsideDepartment of Electronics and Electrical Engineering,

University of Glasgow, Glasgow G12 8LT, United Kingdom

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IntroductionWe report on the hybrid integration of a resonant tunnelling diode (RTD) and a laser diode (LD) (separate RTD and LD chips)Monolithic integration of a resonant tunnellingdiode and laser diode has been achievedThe hybrid circuit was initially built to obtain insight into the fully integrated deviceHybrid circuit has shown a variety of interesting and potentially useful operating regimes

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OutlineOEICs- electronic and optical devices on the same chip Introduction to the RTDTheory of the RTD-LD circuit – the Liénardoscillator Simple oscillator behaviourSynchronised mode of operation Chaotic mode of operationSummary and conclusion

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RTD based Optoelectronic Devices

RTDs features include pronounced nonlinear current-voltage (I-V) characteristic, and very high frequency operation (up to hundreds of GHz).

Integration of a RTD with optical waveguide

Integration of RTD with laser diode

Emittercontact (AuGe)NiAu silica

lightlight

Substrate

collector contact

AlA

sn

InG

aAs

InG

aAs

n In

GaA

sA

lAs

RTDRTD

“Investigation into the integration of a resonant tunnelling diode and an optical communications laser: model and experiment”, Slight, T. J.; Ironside, C. N. IEEE

J. Quant. Elec. 43, 7, 580-587, 2007

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Resonant Tunnelling DiodesA resonant tunnelling diode (RTD) is a device which uses quantum effects to obtain negative differential resistance (NDR).

Illustration of a typical RTD I-V characteristic and the effect of applied bias.

n InGaAs

n InGaAs

Emittern+ InGaAs

Substrate

AlAs

AlAsInGaAsDouble-Barrier{

n+ InGaAsCollector

~10 nm10 nm

DBQW-RTD Structure. The transmission probability for an InGaAs/AlAs RTD.

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Resonant Tunnelling Diode driving a Laser Diode

Representation of electrical connections of the RTD-LD.

Schematic of the RTD-LD circuit. RTD-LD I-V characteristics.

Hybrid Optoelectronic Integrated Circuit based on monolithically integrated RTD-LD

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Model and comparison with experiment

Experimental and modeled I-V curves

Equivalent Liénard’s oscillator circuit

F(V)C

LR

V(t)

Vin(t)= VDC+VAC sin(2πfint)

( ) ( ) ( ) ( ) 0V t H V V t G V+ + =&& &

( ) ( ) ( )dV t i t F Vdt C

−=

The circuit can be described by the following equations:

Which are equivalent to the Liénard’s second-order differential equation:

( ) ( )( ) bV Ri t V tdi tdt L

− −=

Laser model introduced through single mode rate equations

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Model and comparison with experiment

Experimental and modeled optical self-oscillations.

Experimental and modeled electrical self-oscillations.

Optoelectronic Voltage Controlled Oscillator (OVCO): the frequency of the RTD-LD self-sustained oscillations can be tuned by changing the applied DC voltage –it acts as an optoelectronic voltage controlled oscillator (OVCO) – the tuning can be fitted using the Liénard’s model.

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Frequency Division as a function of the frequency of the applied signal

Experimental laser output when RF signals Vin(t)=VACsin(2πfint) are applied:

(a) Experimental spectrum of the laser optical output showing frequency division by 5 when VAC=150 mV and fin=2.5 GHz;

(b) Laser output showing frequency division by 2: VAC=150 mV at 0.9 GHz;

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Synchronisation 2D Map for the RTD-LD – from the theory of the Liénards oscillator

This colour map shows as coloured regions the synchronised areas (each colour represents harmonically related frequencies) as a function of the amplitude and

frequency of the applied signal to the RTD-LD

Nor

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Chaotic behaviour was observed in a RTD-LD circuit with a 790 nm laser diode that self-oscillates around 640 MHz when DC biased at 3.64 V.

Chaos is obtained by injecting a RF signal with constant AC amplitude of 1.5 V and changing the input frequency from 823 MHz to 930 MHz.

Results show a frequency division by 1, 3, 6 then chaos.

RTD-LD – Route to Chaos (1)

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0.0 0.5 1.0 1.5 2.0

-70

-60

-50

-40

-30

-20

fin/3

RF signal 886 MHz

Opt

ical

Out

put (

a. u

.)

Frequency (GHz)

(a) Injection locking (fin/1)

(b) Frequency Division by 3 (fin /3)(c) Frequency Division by 6 (fin/6)

(d) Chaos

(d)

(a) (b)

(c)

RTD-LD – Route to Chaos (2)

0.0 0.5 1.0 1.5 2.0

-70

-60

-50

-40

-30

-20RF signal 823 MHzfin/1

Opt

ical

Out

put (

a. u

.)

Frequency (GHz)

0.0 0.5 1.0 1.5 2.0

-70

-60

-50

-40

-30

-20

-10

RF signal 930.0 MHz

fin/6

Opt

ical

Out

put (

a. u

.)

Frequency (GHz) 0.0 0.5 1.0 1.5 2.0

-70

-60

-50

-40

-30

-20

-10

Broad Spectrum

RF signal 930.1 MHz

Opt

ical

Out

pu (a

. u.)

Frequency (GHz)

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Chaos in the time domain

The input RF frequency is 2.871 GHz, the AC voltage 0.4 V and the DC bias is 3.79 V (~800 MHz self-oscillations)

Electrical Output Laser Diode Output

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Summary and conclusion

The operation of the RTD-LD circuit can be described by a Liénard’s oscillator approach.The model can be used to predict the observed voltage controlled self-sustained oscillations. It can also explain synchronisation and chaotic behaviour of electrical and optical outputs from the RTD-LD circuitApplications include clock recovery and data encryption using optical chaotic signals

Optoelectronic Integration of a �Resonant Tunneling Diode and a Laser DiodeIntroductionOutline Chaos in the time domainSummary and conclusion

Optoelectronic Integration of a Resonant Tunneling Diode...

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