Efficient, compact and low loss thermo-optic phase shifter in silicon.

Area of Science:

• Photonics
• Materials Science
• Electrical Engineering

Background:

• Optical phase modulation is crucial for integrated photonic circuits.
• Existing thermo-optic modulators often suffer from high power consumption and optical loss.
• Silicon-on-insulator (SOI) platform offers advantages for photonic integration.

Purpose of the Study:

• To design and fabricate a resistive heater for efficient and low-loss optical phase modulation in SOI waveguides.
• To optimize heat generation and optical mode overlap while minimizing free-carrier absorption.
• To characterize the performance of the fabricated phase shifter.

Main Methods:

• Designed a novel ridge waveguide geometry with a tailored resistance profile using varied dopant concentrations.
• Fabricated the phase shifter using a CMOS process with oxide cladding and two metal layers.
• Characterized phase-shifting efficiency, modulation bandwidth, and insertion loss.

Main Results:

• Achieved a phase-shifting efficiency of 24.77 ± 0.43 mW/π.
• Demonstrated a -3 dB modulation bandwidth of 130.0 ± 5.59 kHz.
• Measured a low insertion loss of 0.23 ± 0.13 dB across multiple devices.

Conclusions:

• The designed resistive heater enables efficient and low-loss optical phase modulation in SOI waveguides.
• The device is suitable for densely integrated photonic circuits.
• Quantified thermal isolation requirements for thermo-optic devices on the 220 nm SOI platform.