Experimental setup for the pump-probe experiments. SP: short-wave pass filter; PD: photodetector; HWP: zero-order half-wave plate. The SH pulse with a center wavelength of 400 nm served as a pump pulse, whereas a small portion of the fundamental pulse at 800 nm served as a probe pulse. The units of measure for the focal lengths are millimeters. The pump-probe time resolution was estimated to be 90 fs.
Schematic of the carrier relaxation dynamics. The electrons excited via TPA (solid arrows) may be trapped either as small bound polarons or as small free polarons . The dashed lines indicate the possible relaxation pathways.
The pump transmittance measured for MgSLN as a function of , where is the pump peak intensity and is the sample thickness. Solid and dashed lines indicate theoretical fitting curves for ordinary light polarization and extraordinary light polarization , respectively.
Pump-probe transient signals of induced absorption for probe pulses with extraordinary (solid lines) and ordinary (dashed lines) light polarizations: (a) MgCLN (blue), MgSLN (green), (b) UnCLN (cyan), and UnSLN (red). The pump was polarized as an extraordinary wave and had a peak intensity of .
Pump-probe transient signals of induced absorption measured at different pump peak intensities for (a) MgSLN and (b) UnCLN. Both the pump and the probe were polarized as extraordinary waves. (c) The amplitude of the induced absorption estimated at 3 ps is shown as a function the pump peak intensity for MgSLN and UnCLN. The solid lines indicate theoretical fitting curves.
Transient signals of induced absorption measured by the cw-probe method for (a) MgSLN, (b) UnCLN, and (c) UnSLN. The polarization direction of the probe is denoted as or . The induced absorption for MgCLN probed with an ordinary wave is also plotted in (a).
TPA coefficient measured for four LN samples with ordinary and extraordinary light polarizations. Undoped and MgO-doped crystals of congruent composition ratio are referred to as UnCLN and MgCLN, respectively. Undoped and MgO-doped crystals with near-stoichiometric composition ratio are referred to as UnSLN and MgSLN, respectively.
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