Fig. 1. (a) Schematic illustration of the 1.3-GHz ultrafast YDFL with an all-PM architecture. Polarization-maintaining Yb³⁺-doped fiber, PM-YDF; laser diode with PM fiber optical pigtail, PM-LD; polarization-maintaining isolator, PM-ISO; polarization-maintaining wavelength division multiplexer, PM-WDM; dispersive dielectric mirror, DDM; semiconductor saturable absorber mirror, SESAM. (b) Photograph of the cross section of the PM-YDF. (c) Photograph of the cross section of the PM passive fiber (Corning PM-980). (d) Photograph of the DDM coated on the end of the PM-fiber ferule. (e) Photograph of the SESAM that was put on the end of the zirconia ferrule. (f) Low intensity spectral reflectance and the GVD of the SESAM between the PM-YDF and the fiber ferrule.

Fig. 2. Measured variation of the average power of the all-PM YDF oscillator with the launched pump power (976 nm). In recording the data, the average power was recorded after the polarization dependent ISO operating at 1040 nm [in Fig. 1(a)].

Fig. 3. (a) Spectra of the LPSs observed along the 1040-nm PM-ISO for several values of launched pump power. (b) Autocorrelation trace of the LPSs at a launched pump power of 103.5 mW. (c) Laser waveform measured with an oscilloscope and a photodiode having bandwidths of 6 GHz and 25 GHz, respectively. The interval between the intensity peaks is 783 ps. (d) Spectrum of the photodiode signal in the 1.2762–1.2782 GHz region acquired with an RF spectrum analyzer.

Fig. 4. (a) Mode-locked spectrum of the LPSs by rotating the fast axis of the fiber optical pigtail of the DDM at the launched pump power of 103.5 mW. (b) The corresponding RF spectrum in the 1.2760–1.2780 GHz region. The temporal waveform acquired by an oscilloscope and a photodiode is shown in the inset of (b).

Fig. 5. (a) Relative intensity noise (RIN) (blue curve) of the 1.3 GHz LPS train with the all-PM architecture and integrated RIN (green curve) in the 10 Hz–10 MHz frequency region. (b) The corresponding phase noise (blue curve) and the integrated timing jitter (green).