Fig. 1. (a) Configuration of whole setup. HWP, half wave plate; QWP, quarter wave plate; PBS, polarization beam splitter; YDF, ytterbium-doped fiber; LD, pump laser diode; FR, Faraday rotator; NIR, near-infrared part; VIS, visible part. (b) Structure of the tapered PCF spliced to a fiber collimator.

Fig. 2. (a) Mode locking spectrum (black curve) and the generated SC spectra over 0 s (green curve), 3 h (red curve), and 1 day (blue curve). The gray part is the noise floor of the optical spectrum analyzer. Those wavelengths used for fceo and fbeat detections are marked by vertical dashed lines. (b) A photo of the spatially dispersed SC laser beam. The yellow spot on the left is the CW laser at 580 nm.

Fig. 3. (a) Free-running heterodyne beat signals between the comb and the CW lasers at 580, 679, 698, 707, and 813 nm. (b) Free-running beat signal between the comb and the 922 nm CW laser. (c) Free-running fceo signal.