Over the past decade, the mid-infrared (mid-IR) spectral range from ${\sim}{2}\;\unicode{x00B5}{\rm m}$ up to THz has become of increasing interest owing to a wide variety of emerging scientific and technological applications. The region covers important atmospheric windows and covers spectroscopic fingerprints of numerous trace gases, toxic agents, air, water, and soil pollutants, components of human breath, biological tissue, as well as several explosive and narcotic agents. This makes the mid-IR and THz spectrum highly important for a variety of applications in environmental monitoring, free-space transmission, non-invasive disease diagnosis and therapy through breath analysis, minimally invasive surgery, food quality control, imaging, safety and security, and quantum information. The timely progress of mid-IR technology is, thus, vital for future development of modern diagnostic tools for scientific research and industrial applications.

A key component in the advancement of mid-IR science and technology is the development of innovative laser sources with continually improving performance capabilities in terms of wavelength coverage, spectral and spatiotemporal quality, power, efficiency and output stability, and coverage of all timescales from continuous-wave to ultrafast femtosecond domain. This, in turn, relies on progress in material science and the availability of new crystalline solid-state and fiber laser gain media, novel semiconductors, waveguides and chip-based nanostructures, and new nonlinear crystals for the mid-IR. The steady progress in mid-IR materials and laser sources over recent years has paved the way for the development of new device concepts and applications in a multitude of scientific and technological fields.

The feature aims to provide further stimulus for future advancement of mid-IR science, technology, and applications.