In this study, we study the polarization dependence, gain property,
and amplified spontaneous emission in Cr4+: YAG crystal fibers. Cr4+:
YAG crystal has an ultra-wide bandwidth of 300 nm. Cr4+: YAG crystal
fibers fabricated through laser heated pedestal growth technique are
suitable for the applications of fiber amplifiers, fiber lasers, and
broadband light sources.
The experiment results showed that the polarization-dependent loss
has a severe variation as the optical wavelength change. The maximum
polarization-dependent loss was up to 18 dB. The main reason of such a
large polarization-dependent loss is the combination of multimode
interference and the birefringence induced by the non-uniformity of
optical waveguide structure and residue strain in Cr4+: YAG crystal fibers.
Thus, the results of polarization-dependent loss can be used as a feedback
parameter to improve the fabrication process. In the experiment of gain
property, bi-directional pump and double-pass transmission scheme was
adopted and a 0.2 dB net gain was obtained for the first time at signal
wavelength of 1400 nm, pumping wavelength of 1060 nm, and total
pumping power of 2.8 W. It shows that Cr4+: YAG crystal fiber has
potential to be developed as a broadband fiber amplifier. In the
measurement of amplified spontaneous emission spectrum, a wide
bandwidth of amplified spontaneous emission of 300 nm with total power
of 50 £gWwas obtained at 0.2W pumping power condition. The coupling
efficiencies from amplified spontaneous emission to single mode fibers
and multimode fibers were 1.5 % and 9.9 %, respectively. This result
reveals that it has potential to be developed as a broadband light source.
To improve the optical properties of Cr4+: YAG crystal fiber in the
future, improving the uniformity of optical fiber waveguide and reducing
the residue strain in Cr4+: YAG crystal fiber may suppress the
polarization-dependent loss; increasing the fiber length, decreasing the
mode number, and employing a cladding pump technique with a
well-distributed pump power in the crystal fiber to alleviate the excited
state absorption may raise the gain performance and the amplified
spontaneous emission power.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0120111-152229 |
| Date | 20 January 2011 |
| Creators | Kong, De-ming |
| Contributors | Sheng-Lung Huang, Yi-Chung Huang, Szu-Ming Yeh, Wood-Hi Cheng, Jau-Sheng Wang |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0120111-152229 |
| Rights | not_available, Copyright information available at source archive |
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