Mid-Infrared Photonic Integrated Platform Based on Fe-Doped InGaAs Buried in InP

The mid-infrared (mid-IR) spectral range is typically defined from 3 to 20 µm wavelength and has become an important regime for a plethora of industrial or medical purposes, due to the presence of strong absorption lines of many important molecules. This spectral range has been extensively studied during the last two decades, particularly driven by the progress in quantum cascade lasers (QCLs). As next step, the photonic integration of QCLs with low-loss passive waveguides is highly interesting, as it would enable the development of advanced systems with unique features such as high compactness, robustness, reliability or low operating powers. In this regard, and since QCLs are mainly based on III-V group materials, InGaAs/InP-based platforms are particularly interesting for a monolithic integration. Moreover, the wide transparency window of InP and InGaAs semiconductors and the current technological capability to achieve a low effective background doping make these materials very promising for developing low-loss optical waveguides in the mid-IR. For instance, a recent work has demonstrated low propagation losses in the mid-IR based on air-cladded InGaAs-on-InP waveguides operating in TE polarization [1].