Integrated reconfigurable photonic filters based on interferometric fractional Hilbert transforms

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Signal Processing

Background:

• Photonic filters are crucial components in optical communication and signal processing.
• Reconfigurable filters offer flexibility but often require complex structures.
• Fractional Hilbert transformers (FrHTs) provide unique spectral manipulation capabilities.

Purpose of the Study:

• To design and fabricate an integrated reconfigurable photonic filter using FrHTs.
• To demonstrate tunable notch filtering and single sideband suppression.
• To explore applications in instantaneous frequency measurement systems.

Main Methods:

• Fabrication of grating-based FrHTs and an X-coupler on a silica-on-silicon platform using UV grating writing.
• Integration of thermal tuning filaments (microheaters) for optical phase control.
• Analysis of reflection spectrum responses and device performance.

Main Results:

• Achieved photonic FrHTs with up to 200 GHz bandwidth based on apodized planar Bragg gratings.
• Demonstrated tunable photonic notch filters with a 5 GHz linewidth.
• Implemented controllable single sideband suppression filters with a measured 12 dB suppression ratio.
• Proposed a 50 GHz instantaneous frequency measuring system with potential 3 dB improvement.

Conclusions:

• The integrated reconfigurable photonic filter exhibits versatile functionalities, including notch and single sideband filtering.
• Thermal modulation enables precise control over filter characteristics.
• The proposed device holds significant potential for ultrafast all-optical signal processing and measurement systems.