Gold Nanorods as Saturable Absorber for Harmonic Soliton Molecules Generation.

Yiqing Shu,Ge Shen,Penglai Guo,Peng Wang,Xiaohui Li,Guian Li,Jianqing Li

doi:10.3389/fchem.2019.00715

Abstract

Gold nanorods (GNRs) has been investigated in the field of chemistry, optoelectronics, and medicine for their tenability, compatibility, electromagnetics, and excellent photonics properties. Especially, GNRs, used to generate ultrashort pulse, have been studied recently. However, multiple pulses evolution based on GNRs needs to be further explored. In this article, GNRs are synthesized by seed-mediated growth method, characterized systematically and been chosen as saturable absorber (SA) to apply in ultrafast photonics. The GNRs SA presents a saturable intensity of 266 MW/cm2, modulation depth of 0.6%, and non-saturable loss of 51%. Furthermore, a passively mode-locked erbium-doped fiber laser based on GNRs SA with femtosecond pulse is demonstrated. Thanks to the excellent properties of GNRs, by adjusting the cavity polarization direction with the proposed GNRs SA, soliton molecules operation with spectrum modulation period of 3.3 nm and pulse modulation interval of 2.238 ps is directly obtained. For the most important, 9th-order harmonic soliton molecules have been generated in the laser cavity for the first time. It is demonstrated that GNRs can be a novel type of non-linear optical (NLO) device and have potential applications in the field of ultrafast photonics.

Highlights

Many researchers have been attracted by noble metal nano-materials, such as gold, silver, due to the strong non-linear optical (NLO) effects which caused by their surface plasmon resonances (SPR) (Oh et al, 2011; Tsutsui et al, 2011; Huang et al, 2014; Komarov et al, 2015; Fan and Zhang, 2016; Yang et al, 2018)
The results demonstrate that the ultrafast properties of Gold nanorods (GNRs) are accountable for the generation of the fiber laser
GNRs are prepared by seed-mediated growth method and characterized by the technology of scanning electron microscope (SEM), transmission electron microscope (TEM), visible-near infrared (VIS-NIR) absorption which noticed the micro-structure and the absorption of GNRs

Summary

INTRODUCTION

Many researchers have been attracted by noble metal nano-materials, such as gold, silver, due to the strong non-linear optical (NLO) effects which caused by their surface plasmon resonances (SPR) (Oh et al, 2011; Tsutsui et al, 2011; Huang et al, 2014; Komarov et al, 2015; Fan and Zhang, 2016; Yang et al, 2018). Harmonic mode-locking of soliton molecules in EDF laser based on GNRs SA is studied. Increasing the pump power, 9th-order harmonic soliton molecules are generated in the laser cavity for the first time. The saturable intensity is 266 MW/cm, the modulation depth is ∼0.6%, and the non-saturable loss of 51% Based on these experimental results, we apply GNRs as a SA in fiber laser for implementing mode-locking. Pulse sequence and autocorrelation trace of 9th order harmonics soliton molecule under 314 mW of pump power are exhibited in Figures 8D–F, respectively. The soliton molecules and harmonic mode-locking solution but many other kinds of pluses could be generated in a fiber laser, such as soliton rain and noise-like pluses. Thanks to the high optical damage threshold of GNRs we would do more research on composite mode-locked operations based on GNRs SA and investigate the coexistence of multi-soliton dynamics

CONCLUSION

DATA AVAILABILITY STATEMENT