Studies on coupling of optical power to graphene based nano waveguide at 1550 nm for application in photonic integrated circuit

Abstract

Present research deals with lucid analysis on waveguide and photodetector structure for realising efficient photonics integrated circuit at wavelength of 1550 nm. The proposed structure comprises of Raman laser as optical source, waveguide as channel and p-i-n photodiode as photodetector, where Raman lasing source is designed using silicon semiconductor material and the waveguide as well as intrinsic region of p-i-n photodetector is envisaged by using graphene. Further, plane wave expansion (PWE) method is employed to obtain reflectance and absorbance of the proposed graphene based waveguide. Again, the principle of numerical investigation of coupling efficiency between laser to waveguide as well as waveguide to photodetector is based on overlap integral method which is carried out by overlapping of their mode field profiles. Moreover, 3 dB misalignment effect is analysed which is found to be 1.2 μm, 2.2 μm and 1.6 μm for vertical offset, horizontal offset and angular offset respectively in laser to waveguide coupling process. Further, coupling efficiency between waveguide and photodetector is investigated where, computational mechanisms infers that graphene based photodetector delivers a responsivity of 1.1 Amp/watt and negligible dark current of 72 pA, which is apt for realising high coupling efficiency. Eventually, the outcome of present research asserted that overall transmitted efficiency of 94.86% can be accomplished for the proposed structure at the aforesaid wavelength which came up as a good candidate for future photonics integrated circuits.