Depletion-mode carrier-plasma optical modulator in zero-change advanced CMOS

Area of Science:

• Photonics
• Semiconductor device physics
• Integrated circuits

Background:

• Advanced electronics require efficient optical modulators for high-speed data transmission.
• Integrating optical devices with standard microprocessors remains a challenge due to process incompatibilities.

Purpose of the Study:

• To demonstrate a depletion-mode carrier-plasma optical modulator fabricated using a standard 45 nm node silicon complementary metal-oxide-semiconductor (CMOS) process without modifications.
• To enable monolithic integration of optical modulators with state-of-the-art microprocessors and electronics.

Main Methods:

• A novel resonant modulator design utilizing a hybrid microring/disk cavity within the silicon transistor body layer.
• Fabrication in a standard 45 nm node SOI CMOS process, accommodating lateral p-n junctions instead of ridge waveguides.
• Electrical contact via silicon spokes connecting to p and n regions formed by transistor well implants for index modulation.

Main Results:

• Achieved 5 Gbps data modulation at 1265 nm wavelength with a 5.2 dB extinction ratio.
• Demonstrated low energy consumption of an estimated 40 fJ/bit.
• Exhibited broad thermal tuning across 3.2 THz (18 nm) with an efficiency of 291 GHz/mW.

Conclusions:

• The developed modulator is the first of its kind fabricated in a standard CMOS process, enabling zero-change CMOS photonics.
• This technology is crucial for advancing monolithically integrated CMOS photonic interconnects for future electronics.
• The device's performance metrics and fabrication compatibility represent a significant step towards widespread adoption.