Electro¡VAbsorption Modulator has become a very important element in optical fiber communication due to its capability of integrating with other semiconductor devices. In order to get high-speed performance, the small size of waveguides is necessary. But it also brings to high coupling loss, resulting in low optical fiber link. In general, the waveguide mode is elliptical shape with sizes of 1¡Ñ2£gm to 1¡Ñ3£gm, which will definitely lead to high mode mismatch as adapted to conventional single¡Vmode optical fibers of 8£gm circular mode and cause 7~10 dB insertion loss[21]. Typically, micro lens, tapered fibers or taper optical waveguides are used to confine optical fiber mode to waveguide in order to reduce the insertion loss. In the thesis, we have developed a novel structure of tapered optical spot-size mode converter monolithically integrated with traveling-wave electro-absorption modulator (TWEAM) by using whole wet-etching processing.
The optical waveguides are fabricated by wet-etching and subsequent selective undercut etching. By adjusting the wet-etching time, the waveguide core for TWEAM and the tapered spot-size mode converter can thus be engineered. The selective undercut wet etching not only can reduce the optical scattering loss, but also decrease the parasitic capacitance, leading to high optical and microwave transmission of TWEAM. Based on the model described in literature [4-8] and also Beam Propagation Method (BPM), the optical index of epi-layers is used to calculate the three¡Vdimension modal of optical mode and coupling efficiency. The microwave equivalent circuit is used to calculate and design device structure.
In this thesis, the Spot¡VSize Converter monolithically with Traveling¡VWave Electro¡VAbsorption Modulator device is successfully fabricated and demonstrated. TWEAM integrated spot-size optical mode converter is measured and compared with single TWEAM (without converter) with optical wavelength of from 1550nm to 1570nm. The average optical insertion loss of about 4dB is found. The maximum extinction-ratio is about 21dB with modulation efficiency of 21dB/V, E-O response about 12GHz of ¡V3dB bandwidth at 50£[ termination is demonstrated.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0710106-194012 |
| Date | 10 July 2006 |
| Creators | Tsai, Shun-An |
| Contributors | £@en-Yao Huang, Ann-Kuo Chu, Yi-Jen Chiu, Mei-Ying Chang |
| 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-0710106-194012 |
| Rights | not_available, Copyright information available at source archive |
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