Fig. 1. The schematic principle of polarization mode evolution in PM fibers. (a) The ideal PM fiber. (b) The ideal PM fiber with PMD and an angled HWP. (c) The real PM fiber with PMD. (d) The real PM fiber with PMD and amplification.

Fig. 2. The results of simulation. (a) The original pulse. (b) The original spectrum and modulation wave. (c) The modulated pulses versus parameter B. (d) The modulated spectra versus parameter B, which represents the modulation frequency. (e) The modulated pulses versus parameter A, which represents the modulation depth. (f) The modulated spectra versus parameter A.

Fig. 3. Schematic diagram of cross-polarized pulse measurement based on a WP.

Fig. 4. The schematic diagram of the time synchronizing process of two pulses. L is the optical path difference between two beams.

Fig. 5. The schematic diagram of the PM fiber amplifier. C, fiber collimator; WDM, wavelength-division multiplexing; ISO, optical isolator.

Fig. 6. (a) Modulated pulses and (b) spectra versus fiber lengths. (c) Modulated pulses and (d) spectra versus angles of the HWP.

Fig. 7. The comparison of PER for three stages of PM fiber amplifiers, including PM-YDF-6/125, PLMA-YDF-10/125, and PLMA-YDF-25/250 fiber amplifiers.

Fig. 8. (a) The power and PER of the PM-YDF-6/125 fiber amplifier. (b) The spectra of the seed laser and PM-YDF-6/125 fiber amplifier.

Fig. 9. The spectra of the PLMA-YDF-10/125 fiber amplifier versus (a) signal powers and (b) waveplate angles. The spectra of the PLMA-YDF-25/250 fiber amplifier versus (c) signal powers and (d) waveplate angles.

Fig. 10. The basic mechanism of spectral modulations in PM-fiber-based ultrafast laser systems.