Subwavelength silicon nanophotonics

We present a new type of optical waveguide, exploiting subwavelength grating (SWG) effect. We demonstrate subwavelength grating waveguides made of silicon, including practical components operating at telecom wavelengths: input couplers, waveguide crossings and spectrometer chips. SWG technique avoids loss and wavelength resonances due to diffraction effects and allows for single-mode operation with direct control of the mode confinement by changing the refractive index of a waveguide core over a range as broad as 1.6 – 3.5 simply by lithographic patterning. The light can be launched to these waveguides with a coupling loss of <1 dB and with minimal wavelength dependence over a broad wavelength range (1430 – 1630 nm). In addition, these waveguides can cross each other with minimal loss and negligible crosstalk which allows massive photonic circuit connectivity to overcome the limits of electrical interconnects. These results suggest that the SWG waveguides could become key elements for future integrated photonic circuits.