optical nonlinearities in quantum dot lasers for high ... · diode laser: spontaneous emission +...

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

OPTICAL NETWORKS

OPTICAL NONLINEARITIES IN QUANTUM DOT LASERS FOR HIGH-SPEED COMMUNICATIONS

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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

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)

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

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

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

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

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

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)

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

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)

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

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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Heming HUANG

Télécom ParisTech, Université Paris Saclay,

46 rue Barrault, 75013 Paris, France

[email protected]

mailto:[email protected]



optical nonlinearities in quantum dot lasers for high ... · diode laser: spontaneous emission +...

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