Supercontinuum generation in a visible region of 1-µm-band noise-like pulses with high spectral flatness and excellent temporal stability

We demonstrate supercontinuum (SC) generation extending into the visible light region using a novel configuration of a 1-μm-band noise-like pulse (NLP) seed light source and amplifiers for high peak power. Expanding the range of SC source applications requires extending bandwidth. We use high-peak-power NLPs as seed light of SC generation. An NLP consists of a nanosecond envelope encompassing numerous short pulses with distinct spectral components. NLPs enable SC generation with high spectral flatness and excellent temporal stability. The NLP seed light source is a Fabry-Pérot cavity comprising a Faraday rotator mirror (FRM) and a high-reflectivity mirror (HR). The FRM compensates for polarization fluctuations caused by external factors. On the other hand, polarization fluctuations caused by nonlinear polarization rotation (NPR), which depends on the optical intensity, remain uncompensated, resulting in an increased feedback ratio at the polarization beam splitter-HR. Thus, saturable absorption effects occur within the cavity, enabling the oscillation of NLPs. The NLPs were amplified using a master oscillator power amplifier (MOPA) system. The MOPA system is based on two stages of the ytterbium doped fiber amplifier (YDFA). For SC generation, the NLPs were input into a photonic crystal fiber (PCF) with a zero-dispersion wavelength of 1040 nm, serving as a highly nonlinear medium. Additionally, a short wavelength pass filter (SWPF) allows only wavelength components that match the zero-dispersion point of the PCF to be input into it. The results show the proposed configuration generates a broadband and highly flat SC spectrum covering the visible to near-infrared regions, the NLP reaching at an average output power of 183.1 mW. We achieve SC generation with high spectral flatness and temporal stability.