Room-temperature waveguide-integrated photodetector using bolometric effect for mid-infrared spectroscopy...

Area of Science:

• Photonics and Optical Engineering
• Materials Science
• Spectroscopy

Background:

• Waveguide-integrated mid-infrared (MIR) photodetectors are crucial for molecular spectroscopy but face challenges in broadband response, cooling-free operation, and CMOS compatibility.
• Existing strategies struggle to meet the demands for large-scale, cost-effective MIR photonic integrated circuits (PICs).

Purpose of the Study:

• To develop an uncooled waveguide-integrated photodetector for MIR applications.
• To overcome limitations of current MIR photodetectors by utilizing the bolometric effect and free-carrier absorption (FCA) in germanium (Ge).
• To demonstrate a CMOS-compatible solution for broadband MIR photodetection.

Main Methods:

• Integration of a germanium-on-insulator (Ge-OI) PIC architecture.
• Exploitation of the bolometric effect combined with FCA for light absorption.
• Demonstration of label-free sensing of carbon dioxide (CO2) using the integrated device.

Main Results:

• Achieved broadband responsivity of 28.35%/mW across 4030-4360 nm.
• Obtained a noise-equivalent power of 4.03 × 10⁻⁷ W/Hz⁰.⁵ at 4180 nm.
• Successfully demonstrated label-free CO2 gas sensing on-chip.

Conclusions:

• The developed uncooled waveguide-integrated photodetector offers a pragmatic solution for full MIR spectrum coverage using Ge.
• This approach facilitates fully integrated, wavelength-flexible lab-on-a-chip systems.
• Provides a blueprint for CMOS-foundry-compatible MIR PICs, advancing molecular spectroscopy and sensing.