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Published on: November 30, 2012
Laterally tapered undercut active waveguide fabricated by simple wet etching method for vertical waveguide
Fang-Zheng Lin1, Yi-Jen Chiu, Shun-An Tsai
1Institute of Electro-Optical Engineering, National Sun Yat-Sen University, Kaohsiung 80424, Taiwan.
Optics Express
|June 12, 2008
Summary
This study introduces a novel laterally tapered undercut active-waveguide (LTUAWG) for efficient optical spot-size converters (SSCs). The new design simplifies fabrication and demonstrates high performance for optoelectronic integration.
Area of Science:
- Photonics and Optoelectronics
- Materials Science and Engineering
- Integrated Optics
Background:
- Optical spot-size converters (SSCs) are crucial for impedance matching between different optical components.
- Existing SSC designs often involve complex fabrication processes and limited performance.
- There is a need for simplified, high-performance SSC structures for optoelectronic integration.
Purpose of the Study:
- To propose and demonstrate a novel laterally tapered undercut active-waveguide (LTUAWG) for optical spot-size converters.
- To integrate the LTUAWG with an electroabsorption modulator (EAM) for testing.
- To evaluate the performance characteristics, including mode transfer loss and misalignment tolerance.
Main Methods:
- Fabrication of LTUAWG using a selectively undercut-etching-active-region (UEAR) technique on a laterally tapered ridge.
- Monolithic integration of an EAM with the LTUAWG-based vertical waveguide directional coupler (VWGDC).
- Characterization through loss budget analysis, optical transmission testing, misalignment tolerance tests, and far-field angle measurements.
- Validation using 3D beam propagation method (BPM) simulations.
Main Results:
- Achieved an optical mode transfer loss of -1.6 dB between the passive waveguide (PWG) and active waveguide (AWG).
- Demonstrated high efficiency and identical optical transmission relations in both forward and reverse directions.
- Obtained 1dB misalignment tolerance of +/-2.9 µm (horizontal) and +/-2.2 µm (vertical) from the PWG.
- Far-field angle measurements confirmed the mode transformer capability, with values of 6.0° (H) x 9.3° (V) for PWG and 11° (H) x 20° (V) for AWG.
- 3D BPM simulations showed consistent results with experimental measurements.
Conclusions:
- The novel LTUAWG structure offers a simplified fabrication process using wet etching without regrowth.
- The integrated device exhibits excellent performance, including efficient mode transfer and high misalignment tolerance.
- The UEAR processing with in situ monitoring enables reliable submicron-size fabrication.
- This cost-effective and reliable technique holds significant potential for optoelectronic integration.
