Enabling Spectral Diversity in Fiber Laser Systems Architectures and Applications

Abstract

Nonlinear effects occur due to the modification of optical properties of a material medium by the presence of high intensity light such as lasers, resulting in the generation of new frequency components. The availability of low-loss silica fibers has not only led to a revolution in the field of optical communications but also the beginning of a new field of nonlinear fiber optics. Optical fibers have become the nonlinear medium of choice as they can confine high power light over long lengths and provide efficient thermal management. Additionally, fiber laser systems are rugged and compact due to efficient fusion splicing technology and the absence of external optics for alignment. Different applications require fiber lasers having different operating wavelengths, bandwidth, coherence, and/or power. While lasers are typically described as monochromatic or single-frequency sources, it is possible to create lasers with diverse spectral features. Broadband sources such as supercontinuum (SC) or optical frequency comb (OFC) can be generated using nonlinear effects. Depending on the regime of operation, various nonlinear effects become predominant. For example, in case of continuous-wave (cw) anomalously pumped SC, modulation instability (MI) seeded spectral broadening along with the combined effects of Four-Wave Mixing (FWM) and Stimulated Raman Scattering (SRS) results in a broad spectrum. For OFCs, bandwidth scaling is done using FWM. In narrow linewidth systems, Stimulated Brillouin Scattering (SBS) manifests as a threshold phenomenon limiting power scaling. Here, the intensity of scattered light grows exponentially when the incident light exceeds a certain value of threshold power. It was identified that in the aforementioned cases, poor spectral shape and control imposed limitations on system performance and use. In this thesis, we propose simple and easy-to-implement solutions to overcome these shortcomings. Thereby, opening up avenues for these diverse (broadband to narrowband) sources to be used in a wide r...