The nonlinear optical properties of Zirconium pentatelluride and its application in ultrafast solid-state lasers

The topological Dirac semimetal Zirconium pentatelluride (ZrTe5) has many special properties such as anomalous Hall effect and thermoelectric effect. A fast relaxation time constant of 250 fs indicates its great application potential in ultrafast optics, which has been investigated in a Er-doped passively mode-locking fiber laser. In this paper, the ZrTe5 was adopted as a saturable absorber (SA) to modulate Nd-doped solid-state lasers for ultrafast pulse generation. The nonlinear absorption coefficient of ZrTe5 was measured to be −0.81 cm/GW by Z-scan technique. A pulse width of 18.4 ps with a repetition frequency of 69 MHz was gained in the 1.06 μm passively mode-locking laser. For the 1.34 μm ultrafast laser, a stable pulse sequence with a pulse duration of 17.7 ps was delivered and the corresponding repetition frequency was 71 MHz. Those results revealed that ZrTe5 has an excellent laser modulation performance in ultrafast solid-state lasers. As far as we know, it is the first time the solid-state passively mode-locking laser operation by using ZrTe5 as a SA has been successfully demonstrated.