Waveguide-integrated mid-infrared photodetection using graphene on a scalable chalcogenide glass platform

Area of Science:

• Optoelectronics
• Materials Science
• Photonics

Background:

• Compact mid-infrared (mid-IR) spectroscopy is vital for distributed sensing in gas leak detection and environmental monitoring.
• Current mid-IR photonic integrated circuit (PIC) platforms using semiconductors are limited to wavelengths below 4 μm due to material bandgaps and SiO2 substrates.

Purpose of the Study:

• To overcome the wavelength limitations of existing mid-IR PICs.
• To develop a novel PIC architecture for extended mid-IR operation.
• To enhance performance for fieldable spectroscopy devices.

Main Methods:

• Developed a chalcogenide glass-on-CaF2 PIC architecture.
• Integrated split-gate photothermoelectric graphene photodetectors.
• Utilized advanced material science and device fabrication techniques.

Main Results:

• Extended mid-IR operation to 5.2 μm.
• Achieved a Johnson noise-limited noise-equivalent power of 1.1 nW/Hz^1/2.
• Demonstrated no photoresponse fall-off up to 1 MHz with a predicted 3-dB bandwidth exceeding 1 GHz.

Conclusions:

• The novel chalcogenide glass-on-CaF2 PIC platform with graphene photodetectors overcomes previous wavelength limitations.
• This technology enables mid-IR sensing at longer wavelengths, expanding application possibilities.
• The platform is suitable for distributed gas sensing, portable dual comb spectroscopy, and free-space optical communications.