Increasing responsivity-bandwidth margin of germanium waveguide photodetector with simple corner reflector.

Area of Science:

• Optoelectronics
• Semiconductor devices
• Photonics

Background:

• External bandwidth of germanium waveguide photodetectors (PDs) is limited by device length, load, and parasitic effects.
• Shortening PDs improves bandwidth but reduces responsivity, creating a critical trade-off.
• Current designs face limitations in optimizing both bandwidth and responsivity simultaneously.

Purpose of the Study:

• To present a novel scheme for waveguide photodetectors (PDs) that overcomes the trade-off between external bandwidth and responsivity.
• To introduce a method for enhancing optical power absorption in germanium waveguide PDs.
• To enable further size reduction of photodetectors without sacrificing performance.

Main Methods:

• Implementing a design utilizing total internal reflections from corner reflectors at the end of PDs.
• Utilizing standard photolithography for the fabrication of these corner reflectors.
• Integrating the reflector to redirect unabsorbed optical power back into the germanium for enhanced absorption.

Main Results:

• The proposed scheme allows for efficient reflection of optical power back into the germanium waveguide.
• This approach facilitates additional optical absorption, compensating for device shortening.
• The design enables simultaneous enhancement of external bandwidth and responsivity, allowing for smaller device footprints.

Conclusions:

• The corner reflector scheme offers a flexible approach to optimizing germanium waveguide photodetector performance.
• This method effectively addresses the bandwidth-responsivity trade-off, paving the way for next-generation optoelectronic devices.
• The integration of total internal reflection enhances device efficiency and allows for significant size reduction.