All-optical differentiation of sub-picosecond pulses in SOI Bragg gratings

The authors present all-optical differentiators based on Silicon-on-Insulator (SOI) Bragg grating technology. It has been shown that the spectral transfer function required for the realization of an N^th-order all-optical temporal differentiation can be provided by a uniform multiple-π-phase-shifted Bragg grating. The device operates in reflection and consists of a uniform Bragg grating with π-phase-shift sections along its length. The desired spectral response of these devices is achieved within their reflection notch around the Bragg wavelength. Furthermore, the high coupling coefficients of these gratings, in the order of 10²-10³ cm^-1, produce grating responses with notch bandwidths of a few nanometres for device lengths less than 100μm, allowing the processing of sub-picosecond pulses.