Bridging the mid-infrared-to-telecom gap with silicon nanophotonic spectral translation

Extending beyond traditional telecom-band applications to optical interconnects, the silicon nanophotonic integrated circuit platform also has notable advantages for use in high-performance mid-infrared optical systems operating in the 2-8 μm spectral range. Such systems could find applications in industrial and environmental monitoring, threat detection, medical diagnostics and free-space communication. Nevertheless, the advancement of chip-scale systems is impeded by the narrow-bandgap semiconductors traditionally used to detect mid-infrared photons. The cryogenic or multistage thermo-electric cooling required to suppress dark-current noise, which is exponentially dependent on E g/kT, can restrict the development of compact, low-power integrated mid-infrared systems. However, if the mid-infrared signals were spectrally translated to shorter wavelengths, wide-bandgap photodetectors could be used to eliminate prohibitive cooling requirements. Furthermore, such detectors typically have larger detectivity and bandwidth than their mid-infrared counterparts. Here, we use efficient four-wave mixing in silicon nanophotonic wires to facilitate spectral translation of a signal at 2,440 nm to the telecom band at 1,620 nm, across a span of 62 THz. Furthermore, a simultaneous parametric translation gain of 19 dB can significantly boost sensitivity to weak mid-infrared signals. © 2012 Macmillan Publishers Limited. All rights reserved.