Enhanced spectral broadening via self-phase modulation with femtosecond optical pulses in silicon nanowires integrated with 2D graphene oxide films

TL;DR

This paper demonstrates enhanced spectral broadening of femtosecond pulses in silicon nanowires integrated with graphene oxide films, showing significant nonlinear optical performance improvements through experimental and theoretical analysis.

Contribution

It introduces a transfer-free method to integrate graphene oxide films onto silicon nanowires, significantly enhancing their nonlinear optical properties for spectral broadening.

Findings

Spectral broadening factor of up to 4.3 achieved.

Waveguide nonlinear parameter improved by ~3.5.

Effective nonlinear figure of merit increased by ~3.8.

Abstract

We experimentally demonstrate enhanced spectral broadening of femtosecond optical pulses af-ter propagation through silicon-on-insulator (SOI) nanowire waveguides integrated with two-dimensional (2D) graphene oxide (GO) films. Owing to the strong mode overlap between the SOI nanowires and the GO films with a high Kerr nonlinearity, the self-phase modulation (SPM) process in the hybrid waveguides is significantly enhanced, resulting in greatly improved spectral broadening of the femtosecond optical pulses. A solution-based, transfer-free coating method is used to integrate GO films onto the SOI nanowires with precise control of the film thickness. Detailed SPM measurements using femtosecond optical pulses are carried out, achieving a broadening factor of up to ~4.3 for a device with 0.4-mm-long, 2 layers of GO. By fit-ting the experimental results with theory, we obtain an improvement in the waveguide nonlin-ear parameter by a factor of ~3.5 and the effective nonlinear figure of merit (FOM) by a factor of ~3.8, relative to the uncoated waveguide. Finally, we discuss the influence of GO film length on the spectral broadening and compare the nonlinear optical performance of different integrated waveguides coated with GO films. These results confirm the improved nonlinear optical per-formance for silicon devices integrated with 2D GO films.