graphene as saturable absorber for photonics applications farah diana binti muhammad faculty of ...

354 Pages·2014·12.73 MB·English

GRAPHENE AS SATURABLE ABSORBER FOR
PHOTONICS APPLICATIONS

FARAH DIANA BINTI MUHAMMAD

FACULTY OF SCIENCE
UNIVERSITY OF MALAYA
KUALA LUMPUR

2014
GRAPHENE AS SATURABLE ABSORBER FOR
PHOTONICS APPLICATIONS

FARAH DIANA BINTI MUHAMMAD

THESIS SUBMITTED IN FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

DEPARTMENT OF PHYSICS
FACULTY OF SCIENCE
UNIVERSITY OF MALAYA
KUALA LUMPUR

2014
UNIVERSITI MALAYA

ORIGINAL LITERARY WORK DECLARATION

Name of Candidate: FARAH DIANA BINTI MUHAMMAD

I/C/Passport No: 900408-03-5244
Regisration/Matric No.: SHC110042
Name of Degree: DOCTOR OF PHILOSOPHY

Title of Project Paper/Research Report/Dissertation/Thesis (“this Work”):
“GRAPHENE AS SATURABLE ABSORBER FOR PHOTONICS APPLICATIONS”

Field of Study: EXPERIMENTAL PHYSICS

I do solemnly and sincerely declare that:

(1) I am the sole author/writer of this Work,
(2) This Work is original,
(3) Any use of any work in which copyright exists was done by way of fair dealing and for
permitted purposes and any excerpt or extract from, or reference to or reproduction of any
copyright work has been disclosed expressly and sufficiently and the title of the Work and its
authorship have been acknowledged in this Work,
(4) I do not have any actual knowledge nor do I ought reasonably to know that the making of
this work constitutes an infringement of any copyright work,
(5) I hereby assign all and every rights in the copyright to this Work to the University of Malaya
(“UM”), who henceforth shall be owner of the copyright in this Work and that any
reproduction or use in any form or by any means whatsoever is prohibited without the
written consent of UM having been first had and obtained,
(6) I am fully aware that if in the course of making this Work I have infringed any copyright
whether intentionally or otherwise, I may be subject to legal action or any other action as
may be determined by UM.

(Candidate Signature) Date:

Subscribed and solemnly declared before,

Witness’s Signature Date:
Name PROFESSOR DR HARITH AHMAD
Designation

Witness’s Signature Date:
Name DR MOHD ZAMANI ZULKIFLI
Designation
ABSTRACT

Graphene, a single layer of carbon atoms, is nowadays considered a great
candidate to be applied as the saturable absorber (SA) with its desirable optical
characteristics such as ultrafast recovery time and ultrawideband absorption due to its
zero bandgap energy and linear dispersion of Dirac electrons. With its advantage over
semiconductor saturable absorber mirror (SESAM) in terms of the cost, tuning range
and ease of fabrication, graphene has been widely accepted to replace the usage of
SESAM. In this work, several methods of graphene integration onto the fiber ferrule
have been demonstrated, such as by optical deposition method, by sandwiching
graphene thin film between the fiber ferrules and by adhering graphene flakes onto the
fiber ferrule using index matching gel. The saturable absorption properties of the
deposited graphene by each different method is also measured and analysed.

Taking advantage of the unique properties of graphene, the graphene deposited
in this work has been demonstrated for Q-switching operation in various setup
configurations, from basic setup of a simple ring cavity of Erbium doped fiber laser
(EDFL) to a more advanced configuration which enables wavelength tunability by
employing different wavelength selective elements including the tunable bandpass filter
(TBF), arrayed waveguide gratings (AWG) and fiber Bragg gratings (FBG).
Comparison on the Q-switching output performance using different wavelength
selective elements is analysed. In addition, graphene Q-switched EDFL based on
distributed Bragg reflector (DBR) cavity configuration and multiwavelength graphene
Q-switched Brillouin-erbium fiber laser have been demonstrated as well, with each
ii
approach having their own advantages. Furthermore, a Q-switched EDFL based on
graphene oxide as the saturable absorber with a simple deposition method has also been
introduced.

Apart from Q-switching, mode-locking generation based on graphene saturable
absorber is also being demonstrated and investigated using a simple ring cavity EDFL.
To provide the wavelength tunability of the mode locked EDFL, a TBF is inserted into
the cavity as the tuning mechanism. Further investigation on the graphene based mode
locked fiber laser is carried out by using an exotic and highly doped Zirconia-erbium
doped fiber (Zr-EDF) as the gain medium. It is interesting to observe that beyond a
certain pump power, harmonic mode locking takes place. In addition, by incorporating a
Mach Zehnder filter into the cavity, the spectrum tunability of the mode locked Zr-
EDFL is achieved and has been well demonstrated. Further development of this
graphene based Zr-EDFL is carried out by demonstrating it as a pulse source for
supercontinuum (SC) generation with an advantage of low cost, since only a short
length of single mode fiber (SMF) is used as the nonlinear medium.

Moreover, in this work, graphene has been also demonstrated as a saturable
absorber for suppressing the noise and multimode oscillations in the laser cavity, and
acts as the key enabler to produce the single longitudinal mode (SLM) operation in the
EDFL. By heterodyning this SLM laser output and an external tunable laser source
(TLS) at a photodetector, a tunable radio frequency generation can be realized.

iii
ABSTRAK

Graphene, satu lapisan atom karbon, dianggap pada masa kini sebagai bahan
kajian yang hebat untuk diaplikasikan sebagai penyerap boleh tepu (saturable absorber)
yang mempunyai karateristik optik yang diinginkan seperti masa pemulihan yang sangat
pantas dan penyerapan dalam lingkungan jalur lebar yang luas disebabkan jurang tenaga
dalam graphene yang bernilai sifar serta serakan lelurus elektron Dirac. Dengan
kelebihan yang dimiliki oleh graphene berbanding cermin penyerap boleh tepu
semikonduktor (SESAM) dari segi kos, julat penalaan dan kemudahan fabrikasi,
graphene telah diterima pakai secara meluas untuk menggantikan penggunaan SESAM.
Dalam projek kajian ini, beberapa kaedah untuk mengintegrasikan graphene pada
hujung gentian optik telah didemonstrasikan, seperti kaedah deposit secara optikal,
kaedah mengapitkan filem nipis graphene antara kedua-dua hujung gentian optik, serta
kaedah melekatkan kepingan graphene pada hujung gentian optik menggunakan gel
bersesuaian indeks (index matching gel). Sifat-sifat penyerapan boleh tepu bagi
graphene yang telah didepositkan menggunakan keadah-kaedah yang berbeza tersebut
juga diukur dan dianalisis.

Graphene yang didedopositkan dalam projek kajian ini juga telah
didemonstrasikan untuk menghasilkan suis-Q (Q-switching) dalam pelbagai bentuk
konfigurasi eksperimen, bermula daripada konfigurasi asas bagi laser fiber berdop-
erbium (EDFL) dalam kaviti membulat kepada konfigurasi yang lebih berteknologi
yang membolehkan penalaan panjang gelombang menggunakan pelbagai jenis alat
pemilih gelombang yang terdiri daripada penapis boleh laras (TBF), parutan gelombang
iv
teratur (AWG) dan gentian optik berparut Bragg (FBG). Perbandingan antara prestasi
keluaran suis-Q (Q-switching) menggunakan pelbagai jenis alat pemilih gelombang
tersebut juga telah dicerakinkan. Sebagai tambahan, graphene Q-suis EDFL berdasarkan
konfigurasi kaviti pantulan Bragg teragih (DBR) serta graphene Q-suis dalam multi
gelombang berdasarkan laser Brillouin-erbium juga didemonstrasikan, dengan setiap
pendekatan tersebut mempunyai kelebihahan masing-masing yang tersendiri.

Selain Q-suis, penjanaan mod terkunci (mode locking) berdasarkan graphene
sebagai penyerap boleh tepu juga turut didemonstrasikan dan dikaji menggunakan kaviti
membulat EDFL. Untuk menghasilkan penalaan gelombang dalam EDFL bermod
terkunci tersebut, satu TBF dimasukkan ke dalam kaviti tersebut sebagai alat penala
gelombang. Kajian lanjut tentang laser gentian optik bermod terkunci menggunakan
graphene diteruskan dengan menggunakan fiber eksotik Zirconia berdop-erbium (Zr-
EDF) yang mengandungi kandungan dopan yang tinggi sebagai media gandaan. Selain
itu, dengan memasukkan penapis Mach Zehnder ke dalam kavity tersebut, penalaan
spektrum dapat dicapai dan didemonstrasi dengan baik. Graphene Zr-EDFL bermod
terkunci ini juga dikembangkan lagi sebagai sumber denyutan (pulse) untuk penjanaan
‘supercontinuum’ (SC) yang memupunyai kelebihan dari segi kos.

Dalam projek kajian ini juga, graphene juga telah didemonstrasikan sebagai
penyerap boleh tepu untuk menyekat ayunan multimod dalam kaviti laser bagi
membolehkan hanya satu mode membujur (SLM) untuk beroperasi dalam EDFL.
Dengan menggabungkan keluaran laser SLM tersebut dengan satu sumber laser luaran
(TLS), penjanaan frekuensi radio dapat direalisasikan.
v
ACKNOWLEDGEMENTS

Praise be to The Almighty, this thesis would not have materialized without the
help and guidance from my supervisor Prof. Harith Ahmad and my co supervisor, Dr.
Mohd. Zamani Zulkifli. No words can describe my deepest appreciation and gratitude to
Prof. Harith who has not only been patient and tolerant to my quest in seeking
knowledge, but also generous in sharing his expertise, immense knowledge and
experience in this field of photonics.
My personal full-hearted appreciation also goes to my family, especially my
parents, Muhammad Yahya and Habsah Yusuf, as well as my siblings, especially my
sisters Hamizah Muhammad and Mazhani Muhammad for supporting, encouraging and
fully understanding me, in order to make sure that I could complete my Ph.D. degree till
the end. Thank you for your love and for being there for me.
My sincere and heartfelt gratitude goes to Mohd. Faizal Ismail for his
selflessness and generous help in the lab, thank you for your kind assistance and strong
encouragement to complete this thesis. Not forgetting the wonderful support from my
relatives, Husin’s family and Datin Rohimah’s family. Also to those who have directly
or indirectly contributed to the completion of this thesis, my gratitude goes to you.
My appreciation also goes to the members of the Photonic Research Center
especially Dr. Richard, Dr. Chong Wu Yi, Dr. Amirah Abdul Latif, Mohd. Hafizin
Jemangin, Fauzan Ahmad, Prof. Sulaiman Wadi Harun and Encik Khairi. You all have
made the lab most enjoyable to work in despite the many challenges we have to put up
with. Thank you for your continuous support and friendship.
vi
LIST OF ISI PUBLICATIONS

1. Muhammad, F. D., Zulkifli, M. Z., Latif, A. A., Harun, S. W., & Ahmad, H. (2012).
Graphene-based saturable absorber for single-longitudinal-mode operation of highly

doped erbium-doped fiber laser. IEEE Photonics Journal, 4(2), 467-475.
2. Ahmad, H., Muhammad, F. D., Zulkifli, M. Z., Latif, A. A., & Harun, S. W. (2012).
Tunable radio frequency generation using a graphene-based single longitudinal mode

fiber laser. Journal of Lightwave Technology, 30(13), 2097-2102.
3. Ahmad, H., Muhammad, F. D., Zulkifli, M. Z., & Harun, S. W. (2012). Graphene-
oxide-based saturable absorber for all-fiber Q-switching with a simple optical

deposition technique. IEEE Photonics Journal, 4(6), 2205-2213.
4. Ahmad, H., Zulkifli, M. Z., Muhammad, F. D., Jemangin, M. H., Dimyati, K., Pal, B.
P., & Harun, S. W. (2012). Passively Q-Switched 11-channel stable Brillouin
erbium-doped fiber laser with graphene as the saturable absorber. IEEE Photonics

Journal, 4(5), 2050-2056.
5. Ahmad, H., Zulkifli, M. Z., Muhammad, F. D., Samangun, J. M., Abdul-Rashid, H.
A., & Harun, S. W. (2013). Temperature-insensitive bend sensor using entirely
centered erbium doping in the fiber core. Sensors, 13(7), 9536-9546.
6. Thambiratnam, K., Ahmad, H., Muhammad, F. D., Zulkifli, M. Z., Zulkifli, A. Z.,
Paul, M., & Harun, S. W. (2014). Q-switching and mode-locking in highly-doped
Zr O -Al O -Er O doped fiber lasers using graphene as a saturable absorber. IEEE
2 3 2 3 2 3

Journal of Selected Topics in Quantum Electronics, 20(1), 1100108.
vii
7. Ahmad, H., Muhammad, F. D., Zulkifli, M. Z., & Harun, S. W. (2013). Graphene-
based mode-locked, spectrum tunable fiber laser using Mach Zehnder filter. IEEE
Photonics Journal, 5(5), 1501709.
8. Ahmad, H., Razak, N. F., Zulkifli, M. Z., Muhammad, F. D., Munajat, Y., & Harun,
S. W. (2013). Ultra-narrow linewidth single longitudinal mode Brillouin fiber ring
laser using highly nonlinear fiber. Laser Physics Letters, 10(10), 105105.
9. Ahmad, H., Muhammad, F. D., Pua, C. H., & Thambiratnam, K. (2014). Dual-
wavelength fiber lasers for the optical generation of microwave and terahertz
radiation. IEEE Journal of Selected Topics in Quantum Electronics, 20(5), 1-8.
10. Zulkifli, M. Z., Ahmad, H., Taib, J. M., Muhammad, F. D., Dimyati, K., & Harun, S.
W. (2013). S-band multiwavelength Brillouin/Raman distributed Bragg reflector
fiber lasers. Applied Optics, 52(16), 3753-3756.
11. Ahmad, H., Zulkifli, A. Z., Muhammad, F. D., Zulkifli, M. Z., Thambiratnam, K., &
Harun, S. W. (2013). Mode-locked L-band bismuth–erbium fiber laser using carbon

nanotubes. Applied Physics B, 1-6.
12. Ahmad, H., Zulkifli, M. Z., Muhammad, F. D., Zulkifli, A. Z., & Harun, S. W.
(2013). Tunable graphene-based Q-switched erbium-doped fiber laser using fiber
Bragg grating. Journal of Modern Optics, 60(3), 202-212.
13. Ahmad, H., Muhammad, F. D., Zulkifli, M. Z., & Harun, S. W. (2013). Q-switched
pulse generation from an all-fiber distributed Bragg reflector laser using graphene as

saturable absorber. Chinese Optics Letters, 11(7), 071401.
14. Ahmad, H., Zulkifli, M. Z., Muhammad, F. D., Taib, J. M., & Harun, S. W. (2013).
Tunable S-band output based on Raman shift in dispersion shifted fiber. Journal of

Modern Optics, 60(9), 737-740.
viii