Ultra-fast pulse shaping using a graphene hybrid plasmonic temporal differentiator

Abstract

This paper presents the design and analysis of an ultra-compact temporal differentiator (DIFF) based on a graphene hybrid plasmonic all-pass microring resonator (GHP-APMRR) for ultra-short signal processing. Due to the use of graphene hybrid plasmonic waveguide and small ring with a radius of 1033 nm, the overall footprint of the temporal DIFF is equal to 4 × 2.586 μm2. This circuit has a very low insertion loss and a wide 3 dB bandwidth (2.058 to 2.303 THz) for various differentiation orders; so that it is able to process an ultra-short Gaussian input pulse with FWHM of 360 fs. In order to investigate performance of the proposed DIFF for the first and fractional-orders differentiation, its numerical results have been compared with those of the ideal mathematical DIFF in the frequency and time domains. On the other hand, performance of the temporal DIFF as an optical pulse shaper for generating some special pulses such as flat-top, parabolic, and triangular waveforms has been evaluated in detail. By comparing the optical results obtained based on the three-dimensional finite-difference time-domain method with the mathematical functions of the target pulses and the results calculated for the ideal mathematical first order DIFF, it has been illustrated that the GHP-APMRR can accurately generate the flat-top, parabolic, and triangular ultra-short pulses with the temporal FWHM of 600, 500 and 400 fs, respectively.