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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ECIO’08 Eindhoven June 08
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
