We investigated the nonlinear optical properties of ReSe2. First, we measured the nonlinear absorption coefficient and the nonlinear refractive index of a ReSe2 thin film using open-aperture (OA) and closed-aperture (CA) Z-scan techniques. ReSe2 was shown to possess both saturable absorption and self-defocusing properties. The nonlinear absorption coefficient of ReSe2 was measured to be (5.67±0.35)×103cm/GW, and its nonlinear refractive index was (2.81±0.13)×10 2cm2/GW at 1560 nm. Next, a fiberized saturable absorber (SA) based on ReSe2 was fabricated with a side-polished fiber platform and was tested as an ultrafast mode-locker capable of producing femtosecond pulses operating at a wavelength of 1560 nm. The estimated modulation depth and saturation power are ～3.9% and ～42W, respectively, for the transverse electric mode, while they are ～2.4% and ～53W for the transverse magnetic mode. Using the prepared SA, stable soliton pulses with a temporal width of ～862fs were produced from an erbium-doped fiber ring cavity. To the best of the authors’ knowledge, this is the first demonstration of using a ReSe2-based SA for femtosecond mode-locked pulse generation.

We experimentally demonstrate an ultrafast mode-locker based on a CoSb3 skutterudite topological insulator for femtosecond mode-locking of a fiber laser. The mode-locker was implemented on a side-polished fiber platform by depositing a CoSb3/PVA composite. The measured modulation depth and saturation power for the transverse-electric mode input were ～5% and ～8.7 W, respectively, and ～2.8% and ～10.6 W for the transverse-magnetic mode input. By incorporating this mode-locker into an erbium-doped fiber-based ring cavity, we were able to readily generate mode-locked, soliton pulses having a pulse width of ～833 fs at 1557.9 nm. The 3-dB bandwidth of the output pulses and time-bandwidth product were ～3.44 and 0.353 nm, respectively. To the best of the authors’ knowledge, this is the first demonstration of the use of a skutterudite-based saturable absorber for femtosecond mode-locked pulse generation.

The potential of bulk-like WTe2 particles for the realization of a passive Q-switch operating at the 1 μm wavelength was investigated. The WTe2 particles were prepared using a simple mechanical exfoliation method together with Scotch tape. By attaching bulk-like WTe2 particles, which remained on the top of the sticky surface of a small segment of the Scotch tape, to the flat side of a side-polished fiber, a saturable absorber (SA) was readily implemented. A strong saturable absorption was then readily obtained through an evanescent field interaction with the WTe2 particles. The modulation depth of the prepared SA was measured as ～2.18% at 1.03 μm. By incorporating the proposed SA into an all-fiberized ytterbium-doped fiber ring cavity, stable Q-switched pulses were readily achieved.