Fig. 1. Crystal structure of a layered PdS2.

Fig. 2. (a) FETEM image and (b) corresponding high-resolution transmission electron microscopy (HRTEM) image of a randomly selected PdS2 flake; (c) SAED pattern and (d) EDS profile of the PdS2 sample.

Fig. 3. Statistical distribution of lateral size along (a) short axis, (b) long axis, and (c) layer thickness (analyzed from 250 PdS2 flake samples); (d) AFM image of measured PdS2 flakes with respect to the height profile of (e) Flake A and (f) Flake B.

Fig. 4. Experimental setup of passively Q-switched and mode-locked EDFL cavity.

Fig. 5. Optical performance of Q-switched operation. (a) Average output power; (b) repetition rate and pulse duration regarding various optical pump powers; (c) pulse train; (d) single-pulse profile; (e) RF spectrum; and (f) wavelength spectrum at the maximum average output power.

Fig. 6. Nonlinear input intensity-dependent normalized transmittance curve of PdS2-SA at 1564 nm, the recorded (a) maximum and (b) minimum modulation depth condition according to the variation of the polarization state of input light.

Fig. 7. Optical performance of mode-locked operation. (a) Average output power regarding various optical pump powers; (b) and (c) are pulse trains with different time scales; (d) autocorrelation trace of mode-locked pulse; (e) RF spectrum; and (f) wavelength spectrum at 0.55 mW output power.

Fig. 8. Schematic diagram illustrating the photon absorption process within a four-energy level model, where the E0, E1, E2, and E3 are the ground state, first, second, and third excited state, respectively. 1PA and 2PA represent the single-photon absorption and two-photon absorption, respectively. ESA stands for the excited-state absorption.