With the escalating demands for optical communication network system, the need for broadband gain medium in optical communication has increased. Among them, Cr4+:YAG crystal has shown an exceptionally successful broadband amplified spontaneous emission (ASE) light source that fully cover 1.2-1.6 £gm range (3-dB bandwidth up to 265 nm). More recently, we demonstrated the realization of a waveguiding, low-loss, and low-threshold Cr4+:YAG double-clad crystal fiber (DCF) based ultra-broadband ASE light source, optical amplifier, and laser grown by the co-drawing laser-heated pedestal growth technique. These results demonstrate the potential of the Cr4+:YAG DCF for the replacement of the erbium doped fiber in future optical communications.
To further improve the efficiency of Cr4+:YAG DCF based active devices, here we show the difference in thermal expansion coefficients between a YAG core and an inner cladding creates a significant localized strain field by near-field scanning optical microscope (NSOM), which can result in optical confinement and provide the possibility to simultaneously alter the Cr3+ and Cr4+ fluorescence lifetime with varied core dimensions. The results indicate that There exists a nearly zero strain across the entire core with a diameter of ~20 £gm, which is beneficial the higher Cr4+ fluorescence lifetime (+6.43%) and emission cross section (+19.17%) as compared with 11-£gm core.
In addition, we have successfully investigated the near-field modal characteristics of Cr4+:YAG DCF laser and ASE by NSOM. The results demonstrate that the Cr4+:YAG DCF laser produced nearly a single-mode (LP01) output with diffraction-limited beam quality of M2 ~1.1; for ASE, the modal weighting of LP01 decreases from 26% to 15% as the number of modes increases from 4 to 7. The results offer a guideline not only for further fabricating Cr4+:YAG DCF tunable lasers, but for efficiently coupling a broadband ASE light source into a single-mode fiber.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0706110-163156 |
| Date | 06 July 2010 |
| Creators | Chen, Ming-yen |
| Contributors | Cheng-Nan Tsai, Shih-Kun Liu, Yen-Sheng Lin, Wood-Hi Cheng, Sheng-Lung Huang |
| 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-0706110-163156 |
| Rights | not_available, Copyright information available at source archive |
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