Optical frequency combs in the 2 mm waveband for dual comb spectroscopy

Optical frequency combs (OFCs) have become an essential tool in many applications spanning from fundamental research metrology to commercialised technologies for sensing and optical communications [1]. Novel applications of OFC are still emerging, requiring OFCs to operate in a varied range of wavelengths. One wavelength range which has become of increased interest in recent years is the 2 µm waveband, here comprising of wavelengths between 2 µm and 3 µm. The interest in this wavelength range is driven by its applicability in many high-impact fields, including environmental sensing, medical applications, material processing and optical communications [2, 3]. One application space that has driven much of the development of photonic technologies in this wavelength range is optical sensing. Optical sensing covers a broad range of application where information is retrieved from light interacting with an environment. In this chapter, we are going to focus on optical spectroscopy, the method of using light to study a material’s or an environment’s chemical composition. In particular, we are going to focus on the use of OFC sources operating in the 2 µm wavelength range in absorption spectroscopy applications.