Vijay Shekhawat, Photonics

Abstract: 

Optical amplifiers are essential for high throughput optical communication systems. However, traditional rare-earth-doped amplifiers, limited by their relatively narrow optical bandwidths, increasingly constrain the scalability of next-generation fiber networks. Integrated optical parametric amplifiers, based on Kerr nonlinear optics, offer a promising solution by enabling broadband gain across arbitrary wavelengths. Despite this potential, the bandwidths demonstrated to date remain limited, primarily due to insufficient control over higher-order dispersion. Moreover, multimode interference within the waveguides further reduces the usable bandwidth. Additionally, the achievable gain and noise figure are constrained by propagation and coupling losses in these meter-length waveguides. In this work, we demonstrate that rib waveguides fabricated on the silicon nitride (Si₃N₄) platform can support broadband operation through careful design of the waveguide dispersion parameters, specifically β₂ and β₄. By incorporating bends, these waveguides also exhibit pseudo-single-mode behavior, mitigating the effects of multimode interference. Numerical simulations further reveal that rib waveguides with reduced losses can significantly increase the gain and lower the noise figure. These advancements pave the way for practical χ(3)-based nonlinear optical devices that simultaneously deliver high gain, broad bandwidth, and low noise figure.

Main supervisor: Victor Torres Company, Professor 

Examiner: Peter Andrekson, Professor

Discussion leader: Fredrik Laurell, Professor, KTH Royal Institute of Technology