Optical modulator on silicon employing germanium quantum wells

Area of Science:

• Photonics
• Optoelectronics
• Materials Science

Background:

• Electroabsorption modulators are key components in optical communication systems.
• Silicon photonics offers advantages for integration and cost-effectiveness.
• Germanium-based quantum wells provide unique optoelectronic properties.

Purpose of the Study:

• To demonstrate a novel electroabsorption modulator on a silicon substrate.
• To leverage the quantum confined Stark effect in strained germanium quantum wells.
• To achieve high performance and misalignment tolerance for integrated photonic applications.

Main Methods:

• Fabrication of strained germanium quantum wells within silicon-germanium barriers on a silicon substrate.
• Implementation of a side-entry structure with an asymmetric Fabry-Perot resonator.
• Operation at oblique incidence for modulator functionality.

Main Results:

• Achieved a peak contrast ratio of 7.3 dB at 1457 nm with a 10 V swing.
• Maintained a contrast ratio exceeding 3 dB across a 20 nm bandwidth (1441 nm to 1461 nm).
• Demonstrated insensitivity to positional misalignment, with > 3 dB contrast maintained during translations of 87 µm and 460 µm.

Conclusions:

• The demonstrated electroabsorption modulator offers high performance and robustness for silicon photonics.
• The novel side-entry design simplifies integration and packaging by freeing wafer surfaces.
• This technology holds promise for advanced optical interconnects and communication systems.