Lithium niobate waveguide-integrated Bi₂Te₃/graphene heterojunction photodetector

Area of Science:

• Photonics and Materials Science
• Optoelectronics and Nanotechnology

Background:

• Integrated photonic devices require efficient photodetectors for signal processing.
• Lithium niobate on insulator (LNOI) platforms offer excellent optical properties but need improved photodetector integration.
• Graphene and topological insulators like bismuth telluride (Bi2Te3) are promising materials for optoelectronics.

Purpose of the Study:

• To demonstrate an on-chip photodetector by integrating a graphene and Bi2Te3 heterostructure on an LNOI waveguide.
• To investigate the performance enhancement of such a heterojunction photodetector.
• To provide a viable method for self-powered, high-responsivity, and fast-response photodetectors on LNOI platforms.

Main Methods:

• Fabrication of LNOI waveguides using photolithography-assisted chemical mechanical etching.
• Integration of a graphene and Bi2Te3 heterostructure onto the LNOI waveguide.
• Characterization of the photodetector's responsivity, absorption coefficient, and bandwidth.

Main Results:

• The Bi2Te3/graphene heterostructure on the LNOI waveguide achieved a high absorption coefficient of 2.1 dB/µm.
• The photodetector exhibited a responsivity of 2.54 mA/W at 1.55 µm without external bias, a sevenfold enhancement over pure graphene.
• A 3 dB bandwidth exceeding 4.7 GHz was achieved, indicating fast response.

Conclusions:

• The integrated Bi2Te3/graphene heterojunction photodetector demonstrates significantly enhanced performance.
• This approach offers a promising route for developing self-powered, high-performance photodetectors for LNOI photonic integrated circuits.
• The study highlights the potential of combining topological insulators and graphene on LNOI for advanced optoelectronic applications.