Synthesized Graphene Oxide-Decorated Au-Nanorods for Broadband High-Order Harmonic Mode-Locked Fiber Lasers: Experiment and Simulation

Combination of different photonic materials provides vitality for nonlinear optical science and devices. Compared with the traditional gold nanomaterials, graphene oxide-decorated Au-nanorods (GO–AuNRs) can effectively improve the nonlinear optical properties which can operate from the visible to mid-infrared wavelength region. However, the broadband nonlinear optical properties of GO–AuNRs and their application in high-order harmonic ultrafast photonics have been rarely explored so far. In this work, the GO-AuNRs are homemade by an electrostatic self-assembly technique, and the nonlinear absorption properties are experimentally investigated in the C-band and 2 μm region. Through coating the GO–AuNRs onto the side-polished fiber section to assemble the saturable absorber (SA) device, the high-order harmonic operations with 1.048 GHz (51th) and 518.498 MHz (23th) repetition rates are realized in Er3+- and Tm3+-doped fiber lasers, respectively. The monitored long-term stability of mode-locking operation exhibits excellent performance in the C-band and 2 μm region. A well-known nonlinear Schrödinger equation model is utilized to simulate the formation of soliton pulses, and the evolution dynamics of the temporal pulse and soliton spectrum are discussed in detail. The achieved results demonstrate the synthesized GO-AuNRs are suitable for broadband high-order harmonic generation in mode-locked fiber lasers as a promising nonlinear material, which paves the way for exploring novel nonlinear materials for ultrafast photonic devices and nonlinear science.