Integrated InP-InGaAsP tunable coupled ring optical bandpass filters with zero insertion loss

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Semiconductor Devices

Background:

• Monolithic integration of optical filters is crucial for advanced telecommunication systems.
• Tunable optical filters with loss compensation are highly desirable for flexible wavelength management.
• Existing filter technologies face limitations in tunability and integration density.

Purpose of the Study:

• To demonstrate second and third-order monolithically integrated coupled ring bandpass filters.
• To achieve precise generation of optical filters in the RF domain at telecom wavelengths.
• To compensate for device insertion loss and enhance filter performance.

Main Methods:

• Utilized the InP-InGaAsP material system for device fabrication.
• Integrated active semiconductor optical amplifiers (SOAs) and current injection phase modulators (PMs).
• Derived and experimentally validated a Z-transform representation of coupled resonator filters.

Main Results:

• Achieved passband bandwidth tunability from 3.9 GHz to 7.1 GHz for third-order filters.
• Demonstrated stopband extinction up to 40 dB.
• Showcased center frequency tunability over a full free spectral range (FSR) for placement anywhere in the telecom C-band.

Conclusions:

• Monolithic integration of SOAs and PMs with coupled ring filters enables high tunability and precise control.
• The demonstrated filters compensate for insertion loss, enhancing overall device performance.
• The theoretical framework supports the experimental findings, paving the way for advanced tunable optical filters.