Mid-Infrared Wavelength Conversion in Silicon Waveguides Pumped by Silica-Fiber-Based Source

We discuss the potential of four-wave mixing (FWM) in a cascaded silica–silicon platform for generation of light in the midwave infrared (mid-IR) spectral domain. The motivation for developing light sources in mid-IR is supported by numerous applications, such as free-space communications, light detection and ranging (LIDAR), remote sensing, and medicine. These applications would greatly benefit from narrow linewidth and widely tunable laser sources with modulation capability. In this paper, a summary of existing light sources in mid-IR is given and the potential features that the proposed hybrid silica–silicon source can deliver to mid-IR applications are listed. Silica fiber is a well utilized platform at telecom wavelengths that is supported by an excellent infrastructure including tunable narrow linewidth laser sources, unsurpassed in the other spectral domains, high-bandwidth modulators, and detectors. The capability of this platform has recently been extended to the shortwave IR region (SWIR). On the other hand, silicon suffers from impairments imposed by nonlinear absorption at telecom wavelengths, but it possesses excellent linear and nonlinear optical properties in the SWIR (1.7–2.2 μm) and mid-IR (2.2–5 μ m) regions. Therefore, in combination with a silica-based SWIR source, it can be utilized as an efficient FWM platform for mid-IR frequency generation.