Silica Waveguide Thermo-Optic Mode Switch with Bimodal S-Bend.

Area of Science:

• Photonics and Optical Engineering
• Integrated Optics
• Waveguide Devices

Background:

• On-chip optical mode manipulation is crucial for advanced photonic integrated circuits.
• Thermo-optic switches offer a viable mechanism for controlling light propagation in waveguides.
• Developing compact and efficient mode switches is essential for miniaturizing photonic devices.

Purpose of the Study:

• To demonstrate a silica waveguide thermo-optic mode switch utilizing small-radius bimodal S-bends.
• To implement selective output for E11 and E21 modes using a cascaded multimode interference coupler.
• To evaluate the performance of the designed mode switch through detailed characterization.

Main Methods:

• Design optimization using the beam propagation method.
• Fabrication using standard CMOS processes: ultraviolet photolithography, chemical vapor deposition, and plasma etching.
• Characterization of the thermo-optic mode switch performance, including extinction ratio and crosstalk.

Main Results:

• Achieved high extinction ratios (≥13.1 dB for E11, ≥15.5 dB for E21) and low crosstalk (≤-22.8 dB for E11, ≤-18.1 dB for E21) over a wavelength range of 1530-1575 nm.
• Demonstrated efficient mode-selective output for both E11 and E21 modes at low electrical driving powers (284.8 mW and 282.4 mW, respectively).
• Precise fabrication confirmed through detailed characterization of the prepared switch.

Conclusions:

• The study validates the feasibility of employing multimode S-bends for effective thermo-optic mode switching.
• The demonstrated silica waveguide mode switch exhibits favorable performance characteristics.
• The device shows significant potential for future on-chip mode routing applications in photonic integrated circuits.