Fig. 1. Laser polarization conversions of core vector modes. Laser mode over-coupling process is induced by the AOI between the core vector mode HE11y and cladding vector mode TE01, and Λ is the grating period.

Fig. 2. Experimental setup of the tunable ultrafast fiber laser whose mode-locking property and tunability are achieved by an SWCNT-SA and AOI, respectively.

Fig. 3. (a) Photograph of the etched SMF with a diameter of 30 μm. (b) Absorptivity of the fiber-ferule SA with different pump peak intensities and the corresponding nonlinear fitting curve; the inset is the photograph of the SWCNT-SA. The SWCNT film is shown within the red circle.

Fig. 4. Characterization of the tunable band-pass spectral property: (a) conversion of the transmission spectrum from band-injection to band-pass, corresponding to different relative polarization states of PCs 1 and 2; (b) transmission spectra of the AIFG with different driving signal frequencies; (c) corresponding peak wavelengths with different acoustic wave frequencies; (d) AOI wavelength-switch response time.

Fig. 5. Characterization of the soliton operation: (a) output spectra with and without the acoustic wave driving; inset is an enlargement of the local spectrum near the center wavelength; (b) pulse train in time domain; (c) radio-frequency spectrum of the fundamental frequency component; (d) autocorrelation trace and its sech² fitting curve.

Fig. 6. Laser tuning test. (a) Transmission spectra of the AIFG and the output laser with the same driving frequency of 1.049 MHz, where the green shaded area represents the wavelength range within the 3 dB bandwidth of the transmission spectrum. (b) Spectral evolution with increment of the driving frequency from 1.039 to 1.069 MHz. (c) Spectral evolution with a smaller driving frequency interval of 1 kHz, where the two dashed lines are aligned with the corresponding color-coded laser spectra.

Fig. 7. (a) Autocorrelation trace (dashed line) and the sech2 fitting curve (solid line) at each wavelength channel; (b) pulse durations and TBPs with variation of the lasing wavelengths; (c) evolution of the output spectrum during a long-term test of the cavity stability for 90 min; (d) fluctuations of the detected average power and 3 dB spectral bandwidth during the long-term test.