1. Fiber lasers and optoelectronic
devices based on few layers of
graphene
Workshop CPqD / Bristol University Program
Lúcia A. M. Saito
Mackgraphe - Centro de Pesquisas Avançadas em Grafeno,
Nanomateriais e Nanotecnologia
Mackenzie Presbyterian University
2014

2. Outline
Part I - Previous work:
• Actively mode-locking Erbium fiber lasers with meters and kilometers long
• In-field and in-laboratory 50 km ultralong Erbium-doped fiber lasers
Part II - Future Interests:
• Graphene Properties
• Graphene-based optical modulators
– Electroabsorption modulator based on monolayer graphene
– Double-Layer Graphene Optical Modulator
– MZ Graphene Optical Modulator
• Final remarks
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3. Previous work:
Actively mode-locking Erbium fiber lasers
with meters and kilometers long

4. Ultralong Erbium-doped Fiber Lasers
 Length of 10 cavities: 16.4 m to 100.8 km
 Total intracavity loss: 3.7 to 22.9 dB.
 Erbium-doped fiber:
• Absorption coefficient: -33.8 dB/m
• Dispersion coefficient: -57.0 ps/nm.km
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5. 5
Pave = 1.8 mW
Pulse Width as a function of
Dispersion and Cavity Length

6. 6
Analysis of Dispersion and Nonlinearity Length
Setup Lcav LD (km) LNL (km) Lcav / LD Lcav / LNL Analysis
1 16.4 m 36.59 3.06 0.0005 0.0054
I – Neither
dispersive nor
nonlinear effects
2 51.6 m 12.54 2.41 0.0041 0.0214
3 218.0 m 12.74 2.61 0.0171 0.0835
4 1.4 km 11.63 2.56 0.1204 0.5469 II – Nonlinearity-
dominant regime
(Lcav ~ LNL)5 3.0 km 13.49 2.73 0.2224 1.0989
6 12.6 km 14.36 2.80 0.8774 4.5000
III – Dispersion
(Lcav ~ LD)
and nonlinearity-
dominant regime
(Lcav > LNL)
7 25.3 km 18.82 3.26 1.3443 7.7607
8 50.6 km 44.26 4.92 1.1432 10.2846
9 75.7 km 65.85 6.00 1.1496 12.6167
10 100.8 km 83.74 6.76 1.2037 14.9112

7. 7
Possibility of soliton formation in all
cavity setups.
Analysis of Soliton Power and Soliton Period
as a function of D and Lcav
The parameter Z / Lcav is constant
(~1.35) for ultralong cavities.

8. Analysis of Output Spectrum
The profiles of the spectrums confirm the dynamics of pulses in
ultralong cavities. 8

9. 9
In-field
(Kyatera Network)
50 km Ultralong Erbium Fiber Lasers
(in-lab and in-field)

10. 10
Dispersion and nonlinear effects change the pulse
duration at low modulation frequency.
Pulse duration is
shorter than
expected by theory
Output Pulse Width as a function
of Modulation Frequency

11. Future Interests:
Optoelectronic devices based on
few layers of graphene

12. K. S. Novoselov et al., Nature Vol. 490, p.192 (2012).
Graphene-based photonics applications:
Possible application timeline, enabled by continued advances in graphene technologies, based on
projections of products requiring advanced materials such as graphene. The figure gives an
indication of when a functional device prototype could be expected based on device roadmaps
and the development schedules of industry leaders.
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13. Graphene Properties
• High-speed operation. Graphene-based electronics may have the
potential to operate at THz, depending on the carrier density and
graphene quality.
• Strong light-graphene interaction. In comparison to compound
semiconductors, a monolayer of graphene possesses a much stronger
interband optical transition.
• Broadband operation (300 to 2500 nm for SLG). The optical absorption of
graphene is independent of wavelength.
M. Liu et al., Nature, Vol. 474, p.64 (2011).
Objective: to investigate optoelectronic properties and to develop
the photonic devices based on few layers of graphene.
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14. • Monolayer graphene sheet
• Device length: 40 μm
• Broad optical bandwidth: 1350 to 1600 nm.
M. Liu, X. Zhang, paper OTu1l.7, OFC/NFOEC 2012.
Graphene-based optical modulators
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15. Electroabsorption modulator based on
monolayer graphene
Modulation depth:
0.1 dB/ μm
DC measurement of the modulator:
Electro-optics response of the device:
Frequency limit: 1.2 GHz
(measured 3 dB bandwidth)
Drive voltages: 2.0 to 3.5 V
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16. Double-Layer Graphene Optical Modulator
M. Liu, X. Yin, X. Zhang, Nano Letters Vol. 12, p.1482-1485 (2012)
• Modulation depth: ~0.16 dB/μm
• Modulator operates at 1 GHz
• Device length: 40 μm
• Double-layer
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17. Mach-Zehnder modulator
• 8 graphene layers
• Theoretical
• Footprint: 4 x 30 μm2
• High modulation efficiency: 20V. μm
• Large extinction ratio: 35 dB
• Electro-refraction effect
• Variation of effective mode index
neff: 0.028
• Short arm length: 27.57 μm
R. Hao et al., Applied Physics Letters Vol. 103, 061116 (2013) 19

18. Ultra-compact optical modulator by graphene
induced electro-refraction effect
R. Hao, W. Du, H. Chen, X. Jin, L. Yang, E. Li, Applied Physics Letters Vol. 103, 061116 (2013)
• Chemical potential is fixed μc1 = 1 eV.
• Large extinction ratio: 35 dB
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19. Final Remarks
Research Interests:
• Development of optoelectronic devices such as modulators based on few
layers of graphene.
• Pulses generation in Erbium fiber lasers at ultrahigh repetition rates.
Lúcia Saito
lucia.saito@mackenzie.br
Mackgraphe - Centro de Pesquisas Avançadas em Grafeno,
Nanomateriais e Nanotecnologia
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