High-resolution, low-loss multilevel phase shifters based on electrically driven phase-change materials integrated...

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Integrated Optics

Background:

• Multilevel phase shifters are essential for photonic integrated circuits (PICs).
• Achieving non-volatile operation and low insertion loss simultaneously is a key challenge.
• Phase-change materials (PCMs) offer tunable optical properties for phase shifting.

Purpose of the Study:

• To develop a phase shifter with a high number of non-volatile phase levels and low insertion loss.
• To explore the use of germanium selenide (GeSe) as a low-loss PCM in a silicon waveguide platform.
• To design and numerically demonstrate a novel segmented microheater architecture for enhanced phase control.

Main Methods:

• Integration of GeSe PCM with silicon waveguides and microheaters.
• Modification of standard microheaters into a segmented design with gradually increasing width.
• Numerical simulation of pulse-width/pulse-amplitude modulation (PWM/PAM) to induce non-uniform heating and amorphization in GeSe.
• Analysis of phase level generation, spacing, and insertion loss.

Main Results:

• The proposed segmented heater design enables smoother amorphization of GeSe through non-uniform heating.
• A resolution of 164 well-spaced phase levels between 0 and π (>7-bit resolution) was numerically demonstrated.
• Low insertion loss of 0.6 dB (worst case) was maintained in the fully crystalline state.

Conclusions:

• The segmented heater architecture effectively overcomes the limitations of uniform heating for achieving high-resolution multilevel phase shifts.
• This approach provides a promising pathway for advanced, non-volatile, and low-loss phase shifters in PICs.
• The GeSe/microheater platform demonstrates significant potential for next-generation optical signal processing.