Shallow silicon sub-wavelength grating waveguide for electro-optical modulation

One of the most essential components of optical communication systems is the optical modulator. It provides the needed link between both the optical and electrical domains as it converts the incoming electric signal into an optical data stream. Recently, thanks to the huge advancement in the nanolithography and nanofabrication techniques, subwavelength structures with exotic properties have taken the attention of many researchers. In this work, a novel phenomenon is found and intensively studied. Designing the modulator device to operate at the edge between the Bragg reflection and subwavelength regimes results in a peak taking place at the wavelength of interest. Based on this concept, an electro-optical modulator device based on a subwavelength gratings structure utilizing the 70 nm silicon-on-insulator platform is designed. A very low insertion loss of only 0.07 dB, an extinction ratio of about 18 dB, an ultra small capacitance of 27 fF, a very high speed of 118 GHz and an energy consumption of 169 fJ/bit are achieved at the 1550 nm wavelength.