Abstract
Owing to their unique characteristics, two-dimensional (2-D) materials and their complexes have become very attractive in photoelectric applications. Two-dimensional heterojunctions, as novel 2-D complex materials, have drawn much attention in recent years. Herein, we propose a 2-D heterojunction composed of MXene (Ti2CTx) materials and graphene oxide (GO), and apply it to an Nd:YAG solid-state laser as a saturable absorber (SA) for passive Q-switching. Our results suggest that a nano-heterojunction between MXene and GO was achieved based on morphological characterization, and the advantages of a broadband response, higher stability in GO, and strong interaction with light waves in MXene could be combined. In the passively Q-switched laser study, the single-pulse energy was measured to be approximately 0.79 µJ when the pump power was 3.72 W, and the corresponding peak power was approximately 7.25 W. In addition, the generation of a stable ultrashort pulse down to 109 ns was demonstrated, which is the narrowest pulse among Q-switched solid-state lasers using a 2-D heterojunction SA. Our work indicates that the MXene–GO nano-heterojunction could operate as a promising SA for ultrafast systems with ultrahigh pulse energy and ultranarrow pulse duration. We believe that this work opens up a new approach to designing 2-D heterojunctions and provides insight into the formation of new 2-D materials with desirable photonic properties.
Highlights
graphene oxide (GO) solution dispersed in ionic water at 0.5 mg/mL was obtained from a commercial supplier (Nanotechnology, Beijing, China), and MXene (Ti2 C) (99.9%) powder and isopropanol (IPA) solvent were supplied by Aladdin Co., Ltd. (Shanghai, China)
When the MXene–GO material was inserted into the resonator as an saturable absorber (SA), a stable passively Q-switched pulse was obtained with a pump power of 1.61 W
The MXene exhibited an increased absorption signal and improved stability after being combined with GO material, compared to either the MXene material or GO material alone, and better photoelectric performance was achieved for the MXene–GO heterojunction
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The advantages of the different 2-D materials were expected to be combined in such 2-D heterojunctions when incident light passed through the heterojunction boundary, obtaining an optimum photoelectric performance [13] Due to these excellent characteristics, the use of 2-D heterojunctions in photoelectric devices has been reported, such as in solar cells, optical communication devices, and photodetectors [14,15,16,17,18,19,20,21]. SAs, a graphene/Bi2 Te3 2-D heterojunction SA was proposed in recent years and achieved excellent performance in mode-locking operation and Q-switched operation [33] These results indicate that desirable photonic properties could be obtained by employing a 2-D heterojunction; few studies on MXene-based 2-D heterojunctions as SAs applied in passively Q-switched solid-state lasers have been reported, and the mechanism in passively Q-switched solid-state lasers is still unknown. We believe that our work paves the way to designing MXene-based materials to obtain passively Q-switched lasers in the solid state, and indicates that the MXene–GO composite exhibits higher performance in nonlinear optics and acts as a potential 2-D material for photoelectric applications
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