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A novel saturable absorber (SA) was fabricated by coating the topological insulator (TI) film on microfiber using pulsed laser deposition (PLD) method. The TISA device had an insertion loss of ~1.25 dB, a saturable intensity of 26.7 MW/cm2, a modulation depth of ~5.7%, and a nonsaturable loss of 20.5%. Upon employing this SA device, we established a passively mode-locked EDFL and achieved nearly free-chirped soliton pulse with 286 fs of pulse duration and >73 dB of signal to noise ratio (SNR). This result clearly evidences that the PLD is an effective scheme for practical SA device fabrication.

We study the generation of correlated photon pairs via spontaneous four-wave mixing (SFWM) in a 15 cm long micro/nano-fiber (MNF). The MNF is properly fabricated to satisfy the phase-matching condition for generating the signal and idler photon pairs at wavelengths of about 1310 and 851 nm, respectively. Photon-counting measurements yield a coincidence-to-accidental ratio of 530 for a photon production rate of about 0.002 (0.0005) per pulse in the signal (idler) band. We also analyze the spectral information of the signal photons originating from SFWM and Raman scattering (RS). In addition to discovering some unique features of RS, we find the bandwidth of the individual signal photons is much greater than the calculated value for the MNF with homogeneous structure. Our investigations indicate the MNF is a promising candidate for developing the sources of nonclassical light and the spectral property of photon pairs can be used to noninvasively test the diameter and homogeneity of the MNF.

We report on the generation of large pulse duration-tuning and wide wavelength-tunable mode-locked pulses, operating in a dissipative soliton resonance (DSR) region, by an all-normal-dispersion Yb-doped figure-eight fibre laser. For the case of a DSR operating at 1045.1 nm, the pulse duration varies from 26.3 ps to 8.621 ns with the increase of pump power. At the maximum pump power of 400 mW, the pulse energy is as high as 4.8 nJ. In particular, through properly adjusting the polarization controllers, the DSR can be wavelength-tuned in a wide range from 1037.3 to 1075.3 nm. To the best of our knowledge, this is the widest tunable range ever reported for DSR operation. This wavelength-tunable mode-locked fibre laser with a high-energy output may be well-suited for many potential applications.

We demonstrate an all-fiber figure-eight mode-locked thulium-doped fiber laser with a wide tunable range in both pulsewidth and wavelength. A 45-m-long ultrahigh numerical aperture fiber is used to manage the cavity dispersion, and the net cavity dispersion is calculated to be 0.8585 ps 2 at 1900 nm. With net-normal dispersion, the experimental laser, operating in a dissipative soliton resonance region, generates stable rectangular pulses. The pulsewidth varies from 480 ps to 6.19 ns with the increasing pump power, and its center wavelength has a 28.95-nm tunable range (from 1940.22 to 1969.17 nm) by properly adjusting the polarization controllers. The maximum of average output power and pulse energy is 60.73 mW and 19.51 nJ, respectively. The rectangular pulses have a clamped peak power of about 3.16 W. The wavelength-tunable fiber laser with high-energy output operating at 2 "m has great potential in various application fields.

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