Optical nonlinearities in quantum dot lasers for high ... · Diode laser: spontaneous emission +...
Transcript of Optical nonlinearities in quantum dot lasers for high ... · Diode laser: spontaneous emission +...
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Heming Huang
Supervisors: Frédéric Grillot
& Didier Erasme
Optical nonlinearities in quantum
dot lasers for high-speed
communications
Journée de restitution du programme Futur & Ruptures
Paris, le jeudi 2 février 2017 1/16
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OPTICAL NETWORKS
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The new requirements in terms of cost and energy consumption need to be
considered in the design and operation of a new generation of optical sources
Ref: Cisco, The Zettabyte Era: Trends and Analysis, 2016
Strong data traffic increase in telecom/datacom optical networks
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THESIS OBJECTIVES
Developing greener, faster and smaller quantum confined
transmitters with improved performance
Using external control techniques to probe optical nonlinearities in
such transmitters
Applications are but not limited to
o High-speed isolator-free optical transmitters
o Optical wavelength converters for routing light in silicon chips
o Narrow optical linewidth lasers for coherent communications
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OUTLINES
Coherent communications
Narrow linewidth lasers
Quantum dot solutions
Laser stabilization
Summary
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COHERENT COMMUNICATIONS
Enhance the transmission capacity
o Evolution of multiplexing technologies
o Complex modulation formats → coherent communications
Advanced modulation formats
o Intensity & Phase
o Enhance spectral efficiency
→ coherent detection
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Ref: T. Morioka et al., NTT Technical Review, Vol. 9, pp. 8 (2011)
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COHERENT DETECTION
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Direct Detection Coherent Detection
Configuration
Advantages Simple configuration Access to complex signal envelop
Drawbacks Limited in modulation
formats
Received signal is polarization
dependent
Require frequency stabilization &
narrow linewidth
Input Signal
𝐸𝑠
Local Oscillator
𝐸𝐿𝑂
Input Signal
𝐸𝑠
𝐼~𝑅 𝐸𝑠2→ 𝐼𝐷𝐷~𝑅𝑃𝑠
𝐼~𝑅 𝐸𝑠 + 𝐸𝐿𝑂2→
𝐼𝐶𝐷 𝑡 ~𝑅 𝑃𝑠 𝑃𝐿𝑂 exp 𝑖 𝜔𝑠 − 𝜔𝐿𝑂 + 𝜙 𝑡
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RECEIVER ISSUES
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Direct Detection Coherent Detection
Configuration
Advantages Simple configuration Access to complex signal envelop
Drawbacks Limited in modulation
formats
Received signal is polarization
dependent
Require frequency stabilization &
narrow linewidth
Input Signal
𝐸𝑠
Local Oscillator
𝐸𝐿𝑂
Input Signal
𝐸𝑠
𝐼~𝑅 𝐸𝑠2→ 𝐼𝐷𝐷~𝑅𝑃𝑠
𝐼~𝑅 𝐸𝑠 + 𝐸𝐿𝑂2→
𝐼𝐶𝐷 𝑡 ~𝑅 𝑃𝑠 𝑃𝐿𝑂 exp 𝑖 𝜔𝑠 − 𝜔𝐿𝑂 + 𝜙 𝑡
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LASER OPTICAL LINEWIDTH
Diode laser: spontaneous emission + phase-amplitude coupling
𝚫𝝂 =𝚪𝒈𝒕𝒉×𝑹
𝟒𝝅𝑷𝟎𝒏𝒔𝒑 𝟏 + 𝜶𝑯
𝟐
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Output
Power
Population
inversion factor
Phase-amplitude
coupling factor
Ref: M. T. Crowley et al., Advances in Semiconductor Lasers, New York : Academic (2012)
Modal
Gain
𝚫𝝂
Commercial
QW Laser
Nokia
>3 MHz
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CURRENT NARROW LINEWIDTH LASERS
State-of-the art
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Quantum dot technology? Ref: M. Seimetz, OFC/NFOEC, (2008)
Ref: M.R. Matthews et al., Electron. Lett., Vol. 21, pp. 113 – 115 (1985)
Ref: B. Kelly et al., Electron. Lett., Vol. 43, pp. 1282 – 1284 (2007)
Efficient but complex technology
Modulation format QPSK 8PSK 16PSK Square
16QAM
Square
64QAM
Linewidth per laser / data rate 2.4×10-4 3×10-5 6×10-6 3×10-6 3×10-8
Linewidth per laser @ 40Gbit/s 10 MHz 1.6 MHz 240 KHz 120 KHz 1.2 KHz
Current
Standard
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QUANTUM DOT LASERS
Low operating current
Large thermal stability
Isolator-free solutions
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Ref: A. Zilkie, PhD University of Toronto, (2008)
Ref: D. Bimberg et al., Quantum-Dot Heterostructures, Wiley (1998)
Ref: QD Laser White Paper, QD Laser Inc., qdlaser.com
Optical linewidth ?
Courtesy of Dr. P. Poole
QD Layer
QD Laser QW Laser
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QUANTUM DOT SOLUTION (I)
Single-mode laser (distributed feedback)
o Optical filter (grating)
o 5 dot layers
o Lasing wavelength: 1.5 µm
Designed and fabricated in collaboration
with the NRC (Canada)
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Ref: H. Huang, PhD Telecom ParisTech (2017)
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QUANTUM DOT SOLUTION (II)
Figure of merit for narrow linewidth operation
𝚫𝝂 ∝ 𝒏𝒔𝒑 𝟏 + 𝜶𝑯𝟐
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Ref: H. Huang, PhD Telecom ParisTech (2017)
𝒏𝒔𝒑 𝟏 + 𝜶𝑯𝟐
~3.1
~160 KHz
This result is the best ever reported value for a QD DFB laser
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LASER STABILIZATION
A nonlinear control loop
Stable and unstable solutions including chaos (IV)
Efficient laser stabilization (III)
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Laser Delay
Ref: D.M. Kane and K.A. Shore, Unlocking Dynamical Diversity, John Wiley & Sons, Ltd (2005)
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LINEWIDTH NARROWING
Tuning the QD DFB laser into regime III
o Free-running linewidth ~280 kHz
o Linewidth narrows down to 100 kHz
o Laser stabilizes (lower drift)
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Suitable for future coherent communications / chip-scale atomic clock
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SUMMARY
QD technology is simpler for reducing the phase noise
o 160 kHz optical linewidth record value for a QD DFB laser
Using a nonlinear control allows to further narrow the optical linewidth
down to 100 kHz and to stabilize the laser hence reducing the frequency
drift
o Higher order advanced modulation formats
o Chip-scale atomic clocks
Yet to be done
o Further linewidth narrowing is expected from hybrid III-V QD lasers onto silicon
o Coherent detection for silicon photonic applications
o Mid-infrared silicon photonics with quantum cascade lasers
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OPTICAL NONLINEARITIES IN QUANTUM DOT LASERS FOR HIGH-SPEED COMMUNICATIONS
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Heming HUANG
Télécom ParisTech, Université Paris Saclay,
46 rue Barrault, 75013 Paris, France