Celius-SF-515 is a single-frequency ultra-narrow linewidth long coherence length low noise 515 nm (546 available, 515 - 561 nm optional) fiber laser based on a proprietary technology for an intra-cavity doubling of the unpolarised Yb-doped fiber laser with linearly polarized output (patent pending). Cellius-SF-515 key parameter is an ultra-narrow linewidth (< 200 kHz) based on the longitudinal single mode. Celius comes with a piezoelectric tuning with external or built-in (optional) wavelength modulation at kHz bandwidth for locking purposes. Cellius is controlled by the onboard digital display, switches, and adjustment controllers. The control interface software provides optionally.This is a perfect tool for research labs due to excellent performance, high reliability, and lower cost.