Mid-Infrared light emitters based on black phosphorus and its alloys

The mid-infrared (MIR) spectral region is crucial in scientific and technological fields due to its atmospheric transmission windows. These windows enable unhindered infrared radiation transmission, facilitating applications like remote sensing and thermal imaging. Additionally, the MIR region acts as a fingerprint region for various molecules, enabling precise identification and analysis, particularly for greenhouse gases like methane, carbon dioxide, and nitrous oxide. As a result, MIR spectroscopy has become a powerful tool for environmental monitoring and atmospheric studies. Advancing MIR sensing and imaging technologies has recently focused on developing high-performance emitters operating in the MIR band. However, traditional MIR optoelectronics based on III-V or II-VI superlattice materials present challenges in growth complexity, silicon integration, and cryogenic cooling requirements. The emergence of van der Waals (vdW) materials, including black phosphorus (BP), graphene, and semimetals, has shown immense promise as favorable alternatives to conventional materials. Their layered crystalline structure allows for atomic-level manipulation and seamless integration onto photonic structures, eliminating the need for stringent lattice matching. This chapter highlights recent advancements in utilizing BP and its alloys for MIR emission applications. We explore various approaches, including mechanical strain, electric field, and substitutional doping, to engineer their MIR emission wavelengths and the possibility of integrating BP emitters with photonic structures and flexible substrates, facilitating on-chip sensing, communications, and spectroscopy. Additionally, we discuss the challenges of BP-based emitters and potential future breakthroughs aimed at advancing the development of practical and accessible MIR optoelectronic technologies, harnessing novel innovations to revolutionize the field and expand MIR possibilities.