Band structure tuning of g‐C <sub>3</sub> N <sub>4</sub> via sulfur doping for broadband near‐infrared ultrafast photonic applications
Dong Li, Hongwei Chu, Shiping Xu, Ying Li, Shengzhi Zhao, Dechun Li
Abstract
Abstract Graphitic carbon nitride (g‐C 3 N 4 ) featuring a stable heptazine ring structure and high polymerization degree, was indexed as a high thermochemical stability material, attracting rising research enthusiasm for diverse applications. However, the poor near‐infrared (NIR) optical absorption and resulting limited NIR applications were pronounced for g‐C 3 N 4 due to its large bandgap of 2.7 eV. In the present work, sulfur‐doping was manifested by first‐principles calculations to introduce impurity level and result in anisotropic spin splitting in g‐C 3 N 4 for enhancing broadband nonlinear optical characteristics in NIR regime. The modified sulfur‐doped g‐C 3 N 4 (S‐C 3 N 4 ) exhibited the maximum effective nonlinear absorption coefficient to be −0.82 cm/GW. Pulse duration within hundred nanoseconds was realized with high modulation stability employing S‐C 3 N 4 as saturable absorber in Q‐switching operations. Moreover, broadband ultrafast photonics properties were successfully demonstrated in constructed ytterbium‐doped and erbium‐doped fiber lasers, generating highly stable dissipative soliton and traditional soliton mode‐locking pulses. The presented S‐C 3 N 4 nanomaterial with remarkable nonlinear optical performances might explicitly boost the development and application of g‐C 3 N 4 materials in advanced optoelectronic and ultrafast photonic devices.