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Spectrum-continuous narrowband filter with an enhanced flat-top passband and sharp roll-off performance
Optics Letters
|November 1, 2021
Summary
We developed a novel silicon nitride filter using cascaded Mach-Zehnder interferometer (MZI) structures. This advanced optical filter offers exceptional flatness and sharp roll-off, crucial for integrated microwave photonic systems.
Area of Science:
- Photonics
- Integrated Optics
- Optical Filtering
Background:
- Narrowband optical filters are essential components in modern communication systems.
- Existing filters often struggle to balance in-band flatness with sharp out-of-band rejection.
- Silicon nitride photonics offers a robust platform for integrated optical devices.
Purpose of the Study:
- To design and demonstrate a spectrum-continuous narrowband filter with enhanced performance.
- To achieve superior in-band flatness and out-of-band roll-off using cascaded Mach-Zehnder interferometer (MZI) structures.
- To validate the filter's suitability for integrated microwave photonic front-end systems.
Main Methods:
- Utilizing multi-section Mach-Zehnder interferometer (MZI) structures on a silicon nitride platform.
- Cascading multiple MZIs with specific functionalities in series to achieve desired filtering characteristics.
- Fabricating the filter on a single chip with a total waveguide length exceeding 237 cm.
Main Results:
- Demonstration of a four-channel spectrum-continuous filter.
- Achieved a 3 dB bandwidth of 580 MHz and a 1 dB fluctuation bandwidth of 356 MHz.
- Obtained an excellent 20 dB roll-off factor of 1.26, representing a significant advancement.
Conclusions:
- The proposed MZI-based filter achieves unprecedented simultaneous performance metrics.
- The filter's design offers enhanced in-band flatness and sharp out-of-band rejection.
- This technology is highly promising for next-generation integrated microwave photonic systems.
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