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Please use this identifier to cite or link to this item:
http://hdl.handle.net/2031/5549
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| Title: | Cladding-mode coupling and surface-plasmon-mode coupling in conventional and photonic-crystal fibers |
| Other Titles: | Chuan tong he guang zi jing ti guang xian zhong bao ceng mo ou he yu deng li zi ti biao mian mo ou he zhi yan jiu
傳統和光子晶體光纖中包層模耦合與等離子體表面模耦合之研究 |
| Authors: | Lee, Ho Wai (李浩瑋) |
| Department: | Department of Electronic Engineering |
| Degree: | Master of Philosophy |
| Issue Date: | 2008 |
| Publisher: | City University of Hong Kong |
| Subjects: | Integrated optics.
Optical fibers -- Joints. |
| Description: | CityU Call Number: TA1660 .L53 2008
xxii, 139 leaves : col. ill. 30 cm.
Thesis (M.Phil.)--City University of Hong Kong, 2008.
Includes bibliographical references (leaves 119-136) |
| Type: | thesis |
| Abstract: | This thesis presents a series of experimental studies on two dierent physical princi-
ples for the realization of in- ber optical lters: one is based on light coupling from
the ber core to the cladding modes with a long-period ber grating (LPFG) formed
in a conventional single-mode ber or a photonic-crystal ber (PCF); and the other
is based on light coupling from the ber core to the surface plasmon modes in a
gold- lled PCF.
There are many techniques available for the fabrication of LPFGs. The present
study employs a CO2-laser writing technique. Compared with the conventional ultra-
violet writing technique, which is applicable only to photosensitive bers and requires
an amplitude mask, the CO2-laser writing technique is much more exible, as it can
be applied to practically any optical bers and does not require any amplitude mask.
While the CO2-laser writing technique has been demonstrated for grating fabrica-
tion for some years, the physical mechanisms involved in the writing process are not
fully understood. A major contribution of this thesis is to present a detailed study
of the CO2-laser writing dynamics in dierent kinds of bers, including germanium-
doped and boron-doped single-mode bers, and conventional and photonic-crystal
polarization-maintaining bers. The writing dynamics is found to depend strongly
on the CO2-laser energy density and the annealing temperature of the ber. In the
case of a polarization-maintaining ber, the writing e ciency also depends sensitively
on the orientation of the principal axes of the ber with respect to the irradiation direction of the CO2-laser beam, with the highest e ciency obtained when the slow
axis of the ber is aligned with the irradiation direction. These studies reveal the
relative importance of various physical mechanisms in the writing process under dif-
ferent writing conditions and thus provide a better understanding of the formation
and the properties of CO2-laser written LPFGs.
Light coupling to surface plasmon modes in a gold- lled PCF is a new initiative for
the development of optical ber devices. By introducing a single gold nanowire into a
polarization-maintaining PCF, highly polarization- and wavelength-dependent trans-
mission with a plasmon resonance as strong as 45 dB is observed. Near- eld optical
imaging shows that light is guided along the nanowire at the resonance wavelength.
Gold- lled PCFs provide a convenient platform for the study of surface plasmon
excitation and can be further developed into eective wavelength lters and polariz-
ers. Other applications include near- eld ber-tip subwavelength scale imaging and
biomedical sensing. |
| Online Catalog Link: | http://lib.cityu.edu.hk/record=b2340820 |
| URI: | http://hdl.handle.net/2031/5549 |
| Appears in Collections: | EE - Master of Philosophy
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