MLL

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Modelling of an integrated passively modelocked
ring laser for clock recovery
Yohan Barbarin, Erwin Bente, Martijn Heck, Daan
Lenstra and Meint Smit
ESLW Turin 20 Sept. 2003
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Outline

• Introduction to project
• Modelocked laser device
• Modelling
• Conclusions

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Introduction to the project
Clock extraction for application in
OTDM. Injection seeding of a passively
modelocked ring laser Division of clock
frequency 160GHz to 40GHz
Multiplexed optical data with noise and jitter at
160Gb/s
De-multiplexed and regenerated data at 40Gb/s
Clock pulses 40Gb/s
Modelocked laser 40GHz clock extractor
All optical switch
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Integrated mode-locked lasers
One of the four laser designs in InP / InGaAsP
with active-passive integration
Input
Output
MMI
40 GHz FSR cavity
200mm
1000mm
Absorber
Amplifier
Amplifier Forward bias semiconductor bulk
amplifier Saturable absorber reverse bias
semiconductor bulk amplifier
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Modelling

• Numerical modelling in the time domain.
• Unidirectional (at the moment).
• The pulse width lt the cavity length.
• Non self-starting.

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Structure
Input
Output
Coupler
Waveguide Amplifier Absorber BW limit
1000 Time segments of 25fs.
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Amplifier
A SOA is modelled, it is described by the rate
equations
We have divided the SOA in N segments In each
segment Ni uniform W(t) constant in
time Transit time through one segment 25fs
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Absorber
A short SOA reverse biased
N0abs ? N0amp / 2 aabs ? aamp x 4 W(t)
0 tcarAbs ? 30ps (instead of 600ps)
Ref. R.G.M.P.Koumans, R.van Roijen IEEE J. QE
vol. 32 p.478 1996.
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The spectral bandwidth
Dl _at_ -3dB 50nm Dw _at_ -3dB 41x1013 rad/s
A Bessel digital filter is used

• Numerically stable
• The transmission is
• similar to the gain
• spectrum.

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Laser start-up
FWHMinitial 3.0 ps FWHMfinal 1.0 ps after
100 roundtrips
Peak power of the start pulse
10mW Repetition rate 40Ghz Lamp 450µm Labs
47µm Iamp 90mA Tabscar 30 ps
0 400 800 1200
1400 1600 1800
2000
T(ps)
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Clock recovery at 40.1Ghz
Power in W
ps
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Conclusion
This research is supported by the Towards
Freeband Communication Impulse of the technology
programme of the Ministry of Economic Affairs of
the Netherlands
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Parameters
4.229e-20 linear gain coefficient in m2 for the
amplifier 16.0e-20 linear gain coefficient in m2
for the absorber 1.550e-6 wavelength in
m 1.049e24 transparency carrier density m-3 for
the amplifier 0.500e24 transparency carrier
density m-3 for the absorber 2.6202e-16 Bimolecula
r recombination coeff. m3 sec-1 25e-15 length
of one time segment in sec 210 amplifier length
given in number of segments 22 aborber length
given in number of segments 768 passive waveguide
length given in number of segments 200.0 losses
in the waveguide dB/m 1.0e-5 amplifier
spontaneous emission coupling factor to laser
mode 0.1 current through the amplifier in
Amp 0.598e-9 amplifier carrier lifetime in
sec 30.0e-12 carrier lifetime in the absorber
(sec) 5.269e-41 Auger recombination coef in m6
sec-1 3.5 Refractive index -2e-26 Carrier
concentration dependence of refractive
index 14 Bessel Filter order 0.045 bandwidth
normalised frequency
Bessel coefficients
1.073993853104e-9 1.503591394345e-8 9.773344063246
e-8 3.909337625298e-7 1.075067846957e-6 2.15013569
3914e-6 3.225203540871e-6 3.685946903853e-6 3.2252
03540871e-6 2.150135693914e-6 1.075067846957e-6 3.
909337625298e-7 9.773344063246e-8 1.503591394345e-
8 1.073993853104e-9
1.000000000000 -8.793470226997 36.431620104394 -9
4.163898389455 169.480903575400 -224.527211962780
225.623396810498 -174.592705645750 104.48552254255
2 -48.097968574334 16.756598548956 -4.282269732620
0.758553571401 -0.083335436580 4.282411630876e-3
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Amplifier transmission
2.5 2 1.5 1 0.5 0
Initial pulse After Amp.
Power (w)
0 4 8
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Pulse reshaping after the amplifier
T(ps)
Lsoa 400µm Isoa 150mA N(x)1.3x1024 m-3 (on
average)
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Absorber transmission
2.5 2 1.5 1 0.5 0
Initial pulse After Abs.
Pulses centred
Power (w)
0 4 8
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Pulse reshaping after the absorber
T(ps)
Labs 80 µm N(x)1.6x1023 m-3 (on average)
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Program user-interface