Integrated nonlinear photonics with chalcogenide glasses: compositions, properties, applications, and roadmap [Invited]

Research into chalcogenide glass (ChG) waveguides began in the 1970s and gained significant traction through the 1990s, driven by interest in their mid-infrared transparency and strong nonlinear optical properties. Over the past two decades, the field has undergone a transformative shift with the advent of photonic integration–mirroring trends in microelectronics and silicon photonics–enabling miniaturisation, enhanced functionality, and scalable manufacturing. ChG materials, with their unique combination of broadband transparency, high optical nonlinearity, and compositional flexibility, have matured into a robust platform for integrated photonics. These advances have unlocked a rich landscape of nonlinear optical phenomena and enabled applications in signal processing, sensing, and hybrid integration with CMOS-compatible technologies. This review provides a comprehensive survey of the evolution and current state of integrated ChG photonics, with a particular emphasis on nonlinear applications. We also offer a forward-looking perspective on opportunities to improve optical performance, streamline fabrication, expand into emerging application domains, and establish benchmarks for material selection and device design.