1. No category

Ultrafast fiber lasers based on graphene
and other nanomaterials
Grzegorz Soboń
Laser & Fiber Electronics Group
Wrocław University of Technology
Faculty of Electronics
Wybrzeże Wyspiańskiego 27, 50-370 Wrocław, Poland
III Symposium of the Photonics Society of Poland, Warsaw, April 8, 2015
Outline
1. Introduction: mode-locking of fiber lasers & motivation
2. Graphene and its optical properties
3. Ultrafast fiber lasers with graphene
•
•
Experimental results
Our prototype of graphene-based Er-doped laser
4. Other „graphene-like” nanomaterials
•
•
Topological insulators
Black phosphorus (very new!)
5. Summary
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Introduction: Mode-locked lasers
Continuous-wave laser
Mode-locked laser
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A mode-locked laser
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A mode-locked laser – main features
• Emits a train of equally-spaced,
ultrashort pulses (femtosecond) down to single-cycle
• Output spectrum is broad (tenshundreds of nanometers)
Broader spectrum  shorter pulses
• In the frequency domain, it consists
of thousands/millions of narrow
lines (comb-like structure)
Frequency
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Motivation
• Frequency comb stabilization
– Femtosecond lasers emit a „frequency comb”
– High-precision dimensional metrology, optical
atomic clocks, astro-combs…
• Ultra-sensitive laser spectroscopy
– Trace-gas sensing using ultra-sensitive techniques,
like dual-comb spectroscopy or cavity ring-down
sepctroscopy (CRDS)
• Materials processing
– High-quality drilling, cutting, marking, etc.,
– No thermal damage of the material
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Fiber laser mode-locking techniques
• With artificial saturable absorbers:
– Nonlinear Polarization Rotation (NPR)
– Nonlinear Optical/Amplifying Loop Mirror
(NOLM/NALM)
•
•
•
Vulnerable to external
disturbances (e.g.
moving of the fibers)
Not always selfstarting
NPR requires
adjustment
• With „real” saturable absorbers:
•
•
– Semiconductor Saturable Absorber Mirrors (SESAM)
•
Narrow bandwidth
Complex
manufacturing
technology
Problem at 2 μm
• Novel two-dimensional (2D) manomaterials
– graphene, topological insulators (TI), transition-metal
dichalcogenides (TMDC)
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Two-dimensional materials
• 2D material:
– layered material, with single-layer thickness reduced down to
nanometers (atomically-thin)
– strong intra-layer covalent bonding and weak inter-layer van der
Waals forces,
– the electron motion is limited to two dimensions
– Unique optical properties – broadband saturable absorption
• Examples:
–
–
–
–
Graphite/graphene
Topological insulators (Sb2Te3, Bi2Te3, Bi2Se3, etc.)
Transition metal dichalcogenides (MoS2, WS2, etc.)
Phosphorus/Phosphorene
1. M. Xu, T. Liang, M. Shi, and H. Chen “Graphene-Like Two-Dimensional Materials,” Chem. Rev. 113, 3766-3798 (2013)
2. A. H. Castro Neto, and K. Novoselov, “Two-Dimensional Crystals: Beyond Graphene,” Mater. Express 1, 10-17 (2011)
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Types of saturable absorbers
G. Sobon, “Mode-locking of fiber lasers using novel two-dimensional nanomaterials: graphene and topological insulators [Invited],”
Photon. Res. 3, A56-A63 (2015)
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Graphene
Graphene – single layer of carbon atoms,
ordered in a „honeycomb” hexagonal lattice
Nobel Prize in Physics
(2010)
Andre Geim
III Symposium of the Photonics Society of Poland, Warsaw, April 8, 2015
Konstantin
Novoselov
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Optical properties of graphene
•
•
•
Absorption of a single graphene layer: 2.3%
(scales with the number of layers),
The absorption is wavelength-independent,
Due to the 3rd order nonlinearities, it shows saturable
absorption at very low optical intensities
R. R. Nair et al., „Fine Structure Constant Defines Visual Transparency of Graphene”, Science 320, 1308 (2008)
W. B. Cho et al., „High-quality, large-area monolayer graphene for efficient bulk laser mode-locking near 1.25 μm”, Opt. Lett. 36, 4089 (2011)
I. H. Baek et al., „Efficient Mode-Locking of Sub-70-fs Ti:Sapphire Laser by Graphene Saturable Absorber”, Appl. Phys. Express 5, 032701 (2012)
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Saturable absorption measurement
• Fiber connectors
• Free-space coupled saturable absorbers (e.g. graphene on glass)
Research project:
„Investigation of
saturable absorbers
based on graphene oxide
and reduced graphene
oxide” – Dr. J. Sotor
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Saturable absorption in graphene
Saturable absorber model:

 F   Fsat
T ( F )   NS  1  exp 
 T
 
 Fsat   F

Parameters:
ΔT – modulation depth
αNS – non-saturable losses
Fsat – saturation fluence
G. Soboń et al., „Influence of the graphene-based saturable absorber parameters on the performance of an Er-doped fiber laser” –
in preparation
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First demonstration (2009) - Singapore
Parameters:
• Bandwidth: 5 nm
• Rep. rate: 1.74 MHz
• Pulse: 756 fs
Q. L. Bao, H. Zhang, Y. Wang, Z. H. Ni, Z. X. Shen, K. P. Loh and D. Y. Tang, "Atomic layer graphene as saturable absorber for
ultrafast pulsed laser," Adv. Funct. Mater. 19, 3077–3083 (2009)
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Our first experiments (November 2011)
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Mechanically exfoliated graphene
First demonstration of harmonic
mode-locking with graphene
Opt. Commun. 285, 3174–3178 (2012)
Highest repetition rate of a
graphene-based fiber laser
Appl. Phys. Lett. 100, 161109 (2012)
World’s first linearly polarized
graphene-based lasers
Laser Phys. Letters 9, 581–586 (2012)
Opt. Lett. 37, 2166–2168 (2012)
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Graphene manufactured at ITME
(Institute of Electronic Materials Technology)
• CVD Epitaxial graphene [1]:
– Deposition of graphene on copper substrates in the CVD
process,
– Free-standing mono- or multilayer graphene stacks immersed
in polymer foils (e.g. poly(methyl methacrylate) - PMMA)
• „Chemical” graphene – liquid phase exfoliation (LPE) [2]:
– Stable flake-graphene suspensions in various solvents or
polymers (e.g. polivinyl alcohol, chitosan, etc.),
– Also graphene-oxide (GO) and reduced graphene-oxide (rGO)
– Free-standing graphene-oxide paper
[1] T. Ciuk, I. Pasternak, A. Krajewska, J. Sobieski, P. Caban, J. Szmidt, and W. Strupinski, “Properties of Chemical Vapor Deposition Graphene Transferred by High-Speed
Electrochemical Delamination,” J. Phys. Chem. C 117, 20833–20837 (2013)
[2] J. Jagiello, J. Judek, M. Zdrojek, M. Aksienionek, L. Lipinska, „Production of graphene composite by direct graphite exfoliation with chitosan,” Materials Chemistry and
Pysics 148 507-511 (2014)
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UltraGRAPH project
• Financed by the National Centre for Research and
Development (NCBiR) – GRAF-TECH programme
• Project entitled: „Ultrafast, graphene-based fiber lasers” (UltraGRAPH)
• Wrocław University of Technology (Laser & Fiber Electronics Group)
• Institute of Electronic Materials Technology (Warsaw)
• Fiber Optic Technical Support (Wrocław)
• Project objective: develop a prototype of an ultrafast, graphene-based
Er-doped fiber laser
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Ultrafast, graphene-based laser prototype
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Ultrafast, graphene-based laser prototype
Recent results:
Central wavelength
FWHM
Pulse duration
Repetition rate
Average power
Polarization
Dimensions
1555 – 1565 nm
8 – 18 nm
200 – 500 fs
30 – 200 MHz
1 - 5 mW
Linear (all-PM, all-fiber)
140 mm x 25 mm
Previous records:
• 174 fs – Cambridge, D. Popa et al., Appl. Phys. Lett. 97, 203106 (2010)
• 168 fs – Wrocław, J. Tarka et al., Opt. Mater. Express 4, 1981-1986 (2014)
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Ultrafast, graphene-based laser prototype
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Ultrafast, graphene-based laser prototype
•
•
•
•
•
•
•
Fully stable, monolithic construction
Linearly polarized light, PM fiber output
Alignment-free, self-starting (one button)
1000 times ON/OFF test – passed (several times)
Several months of constant operation
No changes in the pulse duration or spectrum shape
Thermally stable (up to 50°C)
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Ultrafast Thulium-doped fiber lasers
• 1900 – 2000 nm wavelength range
covers many absorption lines of
greenhouse gases (CO2, N2O),
• Graphene in combination with PMMA is
an ideal candidate as saturable absorber
for Tm-doped lasers
• Only a very few reports on mode-locked
Tm-doped fiber lasers with graphene
G. Sobon et al., "Thulium-doped all-fiber laser mode-locked by CVD-graphene/PMMA saturable absorber," Opt. Express 21, 12797-12802 (2013)
G. Sobon et al., "All-polarization maintaining, graphene-based femtosecond Tm-doped all-fiber laser," Opt. Express 23, 9339-9346 (2015)
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Ultrafast Thulium-doped fiber lasers
•
•
•
•
Central wavelength: 1940 nm
Bandwidtn: 6.8 nm
Pulse duration: 654 fs
Repetition frequency: 38.5 MHz
G. Sobon, Photon. Res. 3, A56-A63 (2015)
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All-PM ultrafast Tm-doped laser
•
•
•
•
•
•
Central wavelength: 1876 nm
Bandwidtn: 6.6 nm
Pulse duration: 603 fs
Repetition frequency: 41.4 MHz
World’s First all-PM graphene-based laser
Shortest ever pulse generated at 1.9 μm
with the use of graphene
G. Sobon et al., Optics Express 23, 9339-9346 (2015)
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Dual-wavelength laser (1.55 μm + 1.95 μm)
[1] J. Sotor, G. Sobon, J. Tarka, I. Pasternak, A. Krajewska, W. Strupinski, K.M. Abramski, „Passive synchronization of erbium and thulium doped fiber mode-locked lasers
enhanced by common graphene saturable absorber”, Optics Express 22, 5536-5543 (2014)
[2] J. Sotor, G. Sobon, I. Pasternak, A. Krajewska, W. Strupinski, K.M. Abramski, "Simultaneous mode-locking at 1565 nm and 1944 nm in fiber laser based on common
graphene saturable absorber", Optics Express 21, 18994-19002 (2013)
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Passive synchronization of two lasers
J. Sotor, G. Sobon, J. Tarka, I. Pasternak, A. Krajewska, W. Strupinski, K.M. Abramski, „Passive synchronization of erbium and thulium doped fiber mode-locked lasers
enhanced by common graphene saturable absorber”, Optics Express 22, 5536-5543 (2014)
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Passive synchronization of two lasers
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Passive synchronization of two lasers
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Topological insulators
•
•
•
•
Layered, „graphene-like” structure
Isolator in bulk, but with metallic surface states
Over 40 TIs recognized (most popular: Bi2Te3, Bi2Se3, Sb2Te3)
Might be exfoliated mechanically
M. Bianchi et al., Semicond. Sci.
Technol. 27, 124001 (2012)
J.E. Moore, Nature 464, 194-198 (2010)
III Symposium of the Photonics Society of Poland, Warsaw, April 8, 2015
J. Zhang et al., Nano Lett. 11,
2407–2414 (2011)
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First demonstration of a TI-based laser
• Hunan Univ. (China) – November 2012
• Material: bismuth telluride (Bi2Te3) / free-space coupled
• Pulse duration: 1.86 ps
C. Zhao, H. Zhang, X. Qi, Y. Chen, Z. Wang, S. Wen, and D. Tang, “Ultra-short pulse generation by a topological insulator based
saturable absorber,” Appl. Phys. Lett. 101, 211106 (2012)
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Our first laser with TI (Sb2Te3) – April 2013
Microscope image
AFM
SEM
Parameters:
• Rep. rate: 4.75 MHz,
• Pulse duration: 1.8 ps,
• Average power: 0.5 mW
• FWHM: 1.6 nm
World’s first laser with
Sb2Te3 toplogical insulator
J. Sotor, G. Sobon, W. Macherzynski, P. Paletko, K. Grodecki, K. M. Abramski, „Mode-locking in Er-doped fiber laser based on mechanically exfoliated
Sb2Te3 saturable absorber,” Opt. Mater. Express 4, 1-6 (2014)
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Deposition on D-shaped fibers
•
New class of saturable absorbers – the material is deposited on a side-polished fiber
–
–
Increased interaction length (up to several milimeters instead of nanometers)
Larger optical damage threshold (the material interacts only with the evanescent field in the clad)
J. Sotor et al., „Sub-130 fs mode-locked Er-doped fiber laser based on topological insulator”, Optics Express 22, 13244–13249 (2014)
J. Sotor et al., „Mode-locked erbium-doped fiber laser based on evanescent field interaction with Sb 2Te3 topological insulator”, Appl. Phys. Lett. 104, 251112 (2014)
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Sub-130 fs pulse generation
Sub-130 fs pulse generation with Sb2Te3
Output parameters:
• frep= 22.3 MHz,
• pulse = 128 fs,
• Pout = 1 mW
J. Sotor, G. Sobon, K.M. Abramski, „Sub-130 fs mode-locked Er-doped fiber laser based on topological insulator”, Optics Express 22, 13244–13249 (2014)
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Sub-170 fs dissipative soliton generation
• Dispersion-managed cavity
• Sb2Te3 deposited via pulsed magnetron sputtering technique
(collaboration with Warsaw Univ. of Technology & AGH Krakow)
J. Boguslawski et al., „Dissipative soliton generation in Er doped fiber laser mode-locked by Sb2Te3 topological insulator” – in preparation
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Black phosphorus
• Most stable allotrope of phosphorus
• Graphite-like structure
• It has a bandgap (!) scalable with the number of layers, from ~1.5 eV for
phosphorene to ~0.3 eV in bulk
• Might be exfoliated to a single layer – phosphorene
• Exhibits saturable absorption
• Light absorption is polarization-dependent (~10 – 15%)
• No reports on mode-locking using this material
Hugh O. H. Churchill, Pablo Jarillo-Herrero, Nature Nanotechnology 9, 330–331 (2014)
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Black phosphorus-based SA
• Mechanically exfoliated
• 300 nm thick flakes deposited onto the core of the fiber
• Exhibits saturable absorption at 1560 nm (up to ~4.5% modulation depth)
J. Sotor et al., „Black phosphorus – a new saturable absorber material for
ultrashort pulse generation in fiber lasers”, Nature Communications - submitted
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Tm- and Er-lasers with black phosphorus
Er-doped laser:
• pulse = 272 fs,
• λcenter: 1561 nm
• FWHM: 10.2 nm
• frep= 28.4 MHz,
Tm-doped laser:
• pulse = 739 fs,
• λcenter: 1911 nm
• FWHM: 5.8 nm
• frep= 37 MHz,
J. Sotor et al., „Black phosphorus – a new saturable absorber material for ultrashort pulse generation in fiber lasers”, Nature Communications - submitted
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Summary
• Graphene – universal saturable absorber for fiber
lasers operating at different wavelengths,
• Prototype of graphene-based, Er-doped fiber laser,
• Novel saturable absorbers based on 2D-materials:
– Topological insulators
– Black phosphorus (first demonstration)
• 2D materials might replace SESAMs in commercially
available Er- and Tm-doped lasers (broad operation
bandwidth, low saturation fluence, high modulation
depth)
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Funding
„Ultrafast, graphene-based fiber lasers” (UltraGRAPH)
•
•
•
•
•
•
„Saturable absorption in atomic-layer graphene for ultrashort pulse generation in fiber lasers” – OPUS
„Topological insulators as a new class of saturable absorbers for fiber lasers” – OPUS
„Passive mode-locking in dispersion-managed ultrafast Thulium-doped fiber lasers ” – SONATA
„Synchronized mode-locked fiber lasers based on Thulium- and Erbium-doped active fibers as a source for
mid-infrared optical combs generation” - SONATA
„Investigation of saturable absorbers based on graphene oxide and reduced graphene oxide” – Iuventus Plus,
„Amplification of femtosecond pulses from fiber lasers utilizing graphene” – Iuventus Plus.
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Ultrafast fiber laser research group
Head: Prof. Krzysztof M. Abramski
Jarosław
Sotor
Topological
insulators,
black
phosphorus,
graphene
Jakub
Bogusławski
Jan
Tarka
Karol
Krzempek
Grzegorz
Dudzik
Grzegorz
Soboń
Topological
insulators,
dispersionmanaged
lasers
Graphene,
Power
scaling of
Er-lasers,
Tm-lasers
Prototype
(design,
mechanics),
Mid-IR
spectroscopy
Electronics,
LabView
software,
prototype
design
Graphene,
Er-lasers,
Ultrafast Tmlasers,
amplification
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