Dispersion engineered air-clad SiGe waveguides with low propagation loss in the mid-infrared

Summary form only given. Photonic devices operating in the mid-IR (3 μm to 13μm wavelength range) are of great interest for a wide range of applications, such as free-space communications, environmental monitoring or defence. Group IV-based material platforms [1], such as silicon-on-insulator (SOI)[2] and silicon-on-sapphire (SOS)[3] have attracted significant interest for mid-IR integrated photonics. However, absorption in silica beyond 3.5 μm and in sapphire beyond 5.5 μm eventually limits the operational wavelength band of these platforms. More recently, silicon-germanium (SiGe) alloys, with a transparency window potentially extending up to 13 μm depending on the Ge content [4] have emerged as an attractive alternative platform for mid-IR photonics [5-7]. In [6, 7] we reported Si
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Ge
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waveguides buried-in silicon with propagation loss of around 1dB/cm at 4μm, and nonlinear properties somewhat comparable to crystalline silicon between 3.5μm and 5μm.