Silicon photonic devices realized on refractive index engineered subwavelength grating waveguides-A review

It is a remarkable and straightforward approach to customize the dispersion and nonlinear properties of the photonic devices without varying the composition of the material by employing periodic segmented waveguide structures at the subwavelength level of the operational wavelength. This method addresses the diffraction limit and it is likely to engineer the waveguides as a uniform optical medium with an effective refractive index that relies on the waveguide geometry. In recent years, advances in lithographic technology in the semiconductor-on-insulator platform providing sub-100-nm patterning resolution have been renowned with many useful devices based on subwavelength structures. At the beginning of the paper, the modal characteristics of the subwavelength grating (SWG) waveguides are presented. And in afterwards, we provide an insight into noteworthy progress in the subwavelength grating (SWG) waveguides based devices for signal processing and sensing applications such as ring resonators for surface and bulk sensing, couplers, suspended membrane waveguides for mid-infrared applications, filters, and fiber-to-chip couplers.