Midinfrared supercontinuum generation from 2 to 6  μm in a silicon nanowire

Silicon has attracted great interest as a platform for both linear and nonlinear integrated photonics for over 15 years. While its primary applications have been in the telecom window (near 1.5 mu-m), the capability of exploiting its full transparency window to 8 mu-m in the mid-IR is highly attractive, since this will open it up to entirely new applications in fields such as spectroscopy, chemical and biological sensing, and free-space communications. However, while silicon-on-insulator has shown great promise just beyond the telecommunications window [to the shortwave IR band (2.5 mu-m)], its wavelength range has been limited to < 4 mu-m by absorption in the silica cladding layer. Here, we demonstrate octave-spanning supercontinuum generation in silicon, covering a continuous spectral range from 1.9 to beyond 6 mu-m in dispersion-engineered silicon-on-sapphire (SOS) nanowires. This represents both the widest spectrum and longest wavelength generated to date in any silicon platform, and establishes SOS as a promising new platform for integrated nonlinear photonics in the mid-IR.