Ultrafast electro-optical disk modulators for logic, communications, optical repeaters, and wavelength converters.

Area of Science:

• Photonics and Optical Engineering
• Semiconductor Device Physics
• Integrated Optics

Background:

• State-of-the-art vertical pn junction microdisk electro-optical (EO) modulators face limitations in junction-mode overlap.
• Improving speed and power efficiency in EO modulators is crucial for next-generation optical communications.

Purpose of the Study:

• To propose and implement a novel U-shaped pn junction design for silicon-on-insulator microdisk resonators.
• To enhance the junction-mode overlap and reduce parasitic capacitance in EO modulators.
• To demonstrate the potential of this design in various high-performance optical devices.

Main Methods:

• A U-shaped pn junction was designed and integrated into a silicon-on-insulator microdisk resonator.
• The junction depletion zone was maximized to overlap with the whispering gallery optical mode.
• The p-region of the npn-sequenced U-junction was fully depleted to minimize capacitance.

Main Results:

• The U-shaped pn junction design effectively doubled the junction-mode overlap.
• Capacitance was reduced below 3 fF, leading to significant improvements in speed and power performance.
• Devices including EO modulators, switches, and logic gates operated at 7.6-50 GHz with ultralow energy consumption (0.4-9.8 fJ/bit).

Conclusions:

• The depleted U-junction design offers high efficiency and maximizes operating bandwidth.
• CMOS-compatible materials and fabrication-feasible dimensions make this design promising for next-generation applications.
• The proposed devices hold significant potential for high-volume electro-optical communications and computing circuits.