Enhanced Self‐Phase Modulation in Silicon Nitride Waveguides Integrated With 2D MoS 2 Films

ABSTRACT On‐chip integration of 2D materials provides a promising route toward next‐generation integrated optical devices with performance beyond existing limits. Here, significantly enhanced spectral broadening induced by self‐phase modulation (SPM) is experimentally demonstrated in silicon nitride (Si 3 N 4 ) waveguides integrated with 2D monolayer molybdenum disulfide (MoS 2 ) films. Monolayer MoS 2 films with ultrahigh optical nonlinearity are synthesized via low‐pressure chemical vapor deposition (LPCVD) and subsequently transferred onto Si 3 N 4 waveguides, with precise control of the film coating length and placement achieved by selectively opening windows on the chip silica upper cladding. Detailed SPM measurements at telecom wavelengths are performed using fabricated waveguides with various MoS 2 film coating lengths. Compared to devices without MoS 2 , increased spectral broadening of sub‐picosecond optical pulses is observed for the hybrid devices, achieving a broadening factor of up to ∼2.4 for a device with a 1.4‐mm‐long MoS 2 film. Theoretical fitting of the experimental results further reveals an increase of up to ∼27 fold in the nonlinear parameter (γ) for the hybrid MoS 2 /Si 3 N 4 waveguides and an equivalent Kerr coefficient ( n 2 ) of MoS 2 nearly 5 orders of magnitude higher than Si 3 N 4 . These results confirm the effectiveness of on‐chip integration of 2D MoS 2 films to enhance the nonlinear optical performance of integrated photonic devices.