A tunable notch filter using microelectromechanical microring with gap-variable busline coupler.

Area of Science:

• Photonics and Microelectromechanical Systems (MEMS)

Background:

• Wavelength-selective filters are crucial components in optical communication systems.
• Existing tunable filters often face challenges with power consumption and hitless operation.

Purpose of the Study:

• To propose and experimentally investigate a microelectromechanical tunable notch filter.
• To demonstrate a hitless wavelength-selective switching capability.
• To explore the use of silicon-photonic freestanding waveguides in tunable filters.

Main Methods:

• Fabrication of a tunable microring resonator using freestanding single-mode waveguides and air-gap directional couplers.
• Integration of an electrostatic comb-drive actuator to vary the microring's optical path length.
• Implementation of a gap-variable waveguide coupling mechanism for busline switching, also driven by electrostatic actuators.

Main Results:

• Achieved a resonant wavelength shift of 9.96 nm at 26 V with a 1.0 μm actuator displacement.
• Demonstrated adjustable coupling from switch-off (600 nm gap) to critical coupling (383 nm gap).
• The compact device (150 μm x 80 μm) exhibited negligible power consumption due to capacitive actuation.

Conclusions:

• The proposed microelectromechanical tunable notch filter effectively integrates wavelength tunability and hitless switching.
• Freestanding silicon-photonic waveguides and electrostatic actuators enable compact, low-power optical filtering.
• The device shows promise for advanced optical communication and signal processing applications.