Electro-optically tunable polarization independent add drop filter with relaxed beam splitters in LiNb)₃ /
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| Other Authors: | |
| Format: | Thesis eBook |
| Language: | English |
| Published: |
[College Station, Tex.] :
[Texas A&M University],
[2010]
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| Subjects: | |
| Online Access: | Link to OAK Trust copy |
| Abstract: | A polarization-independent electro-optically tunable add/drop filter utilizing non-polarizing novel relaxed beam splitters has been developed in LiNbO3 at the 1.55μm wavelength regime. The operation of this filter is based on passive directional coupler type beam splitters and strain-induced phase-matched TE [left right arrow] TM polarization mode converters on an asymmetric Mach-Zehnder interferometer waveguide configuration. Fabrication parameters for channel waveguides, relaxed beam splitters and polarization mode converters were optimized individually then integrated to produce the final device. Single mode channel waveguides for both TE and TM polarizations were realized by the diffusion of 7[mu]m wide Ti strips into LiNbO3 substrate. Relaxed beam splitters were produced using Ti diffused waveguides in a directional coupler configuration with 3.5mm long coupling region, 0.6° bending angle, and separation gap of 11[mu]m and 13[mu]m between waveguides. Tunable TE[left right arrow]TM polarization mode converters with 99.8% conversion efficiency were obtained using a strain-induced refractive index grating consisting of 500 parallel strips formed in a strained SiO2 surface film with a spatial period of 21[mu]m. The strain results from the thermal expansion mismatch between the film and substrate by depositing the SiO2 surface film at an elevated substrate temperature then cooling down to room temperature. Polarization independent electro-optically tunable add/drop filters were then produced based on the optimized fabrication parameters of the splitters and the mode converters. Fiber-to-fiber insertion loss on a 45mm long filter device was measured to be less than 6.5dB for both TE and TM polarizations. At the express port, the output spectrum of the filter revealed an approximately 13dB notch without an applied voltage, and the spectral characteristics of the drop port showed a -3dB bandwidth of 2.3nm. The nearest sidelobes were about 10dB below the center peak. Electro-optic tuning of the filter device was demonstrated by applying DC voltages ranging between -100V to +100V. A tuning range of 15.7nm with a linear voltage tuning rate of 0.075nm/V for both the TE and TM polarizations were obtained. The filter has a fast response time. The measured rise and fall times are 22.4ns and 45.6ns, respectively. |
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| Item Description: | "Major Subject: Electrical Engineering" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Electronic resource. |
| Physical Description: | 1 online resource. |
| Bibliography: | Includes bibliographical references. |