Fig. 1: Principle for full-spectrum white laser generation.

a Schematic diagram illustrating simultaneous broadband 2nd–10th HHG via cascaded 2nd-NL QPM up-conversion driven by a mid-IR pump femtosecond laser transporting in CPPLN. b Schematic diagram illustrating ultrabroadband 2nd–10th HHG supercontinuum white laser created under the pump of a high-peak-power mid-IR femtosecond laser via synergic action of 2nd-NL and 3rd-NL. c The mechanism of full-spectrum laser generation through a cascaded HCF-LN-CPPLN module via synergic 2nd-NL and 3rd-NL. d Schematic diagram for the structural geometry of the designed CPPLN crystal for HHG. e Optical microscopic image of the etched sample surface of a typical CPPLN structure. f Enlarged views of the positive and negative domains of the CPPLN sample. g Combined plots of the phase-mismatch curve for SHG process in a homogeneous LN crystal and the Fourier coefficient curves for the designed CPPLN sample in 2nd–10th HHG processes, which are divided into six QPM bands