Nonlinear optical property measurements of rhenium diselenide used for ultrafast fiber laser mode-locking at 1.9 μm
Jinho Lee, Suh‐young Kwon, Taeyoon Kim, Junha Jung, Luming Zhao, Jeong Hyeon Lee
Abstract
Abstract An experimental investigation into the nonlinear optical properties of rhenium diselenide (ReSe 2 ) was conducted at a wavelength of 1.9 μm using the open-aperture and closed-aperture Z-scan techniques for the nonlinear optical coefficient (β) and nonlinear refractive index ( n 2 ) of ReSe 2 , respectively. β and n 2 measured at 1.9 μm were ~ − 11.3 × 10 3 cm/GW and ~ − 6.2 × 10 –2 cm 2 /GW, respectively, which to the best of our knowledge, are the first reported measurements for ReSe 2 in the 1.9-μm spectral region. The electronic band structures of both ReSe 2 and its defective structures were also calculated via the Perdew–Becke–Erzenhof functional to better understand their absorption properties. A saturable absorber (SA) was subsequently fabricated to demonstrate the usefulness of ReSe 2 for implementing a practical nonlinear optical device at 1.9 μm. The 1.9-μm SA exhibited a modulation depth of ~ 8% and saturation intensity of ~ 11.4 MW/cm 2 . The successful use of the ReSe 2 -based SA for mode-locking of a thulium–holmium (Tm–Ho) co-doped fiber ring cavity was achieved with output pulses of ~ 840 fs at 1927 nm. We believe that the mode-locking was achieved through a hybrid mechanism of saturable absorption and nonlinear polarization rotation.