Two-dimensional transition metal dichalcogenides are of great interest for second harmonic generation due to their large second-order susceptibility χ^((2)),atomically thin structure,and relaxed phase-matching condit...Two-dimensional transition metal dichalcogenides are of great interest for second harmonic generation due to their large second-order susceptibility χ^((2)),atomically thin structure,and relaxed phase-matching conditions.Such materials are also promising candidates for miniaturizing nonlinear optical devices for versatile applications in photon manipulation,quantum emission and sensing,and nanophotonic circuits.However,their strong second harmonic response is limited by nanometer-scale light-matter interaction and material impurities.Although there is considerable work toward engineering these materials for enhancing their nonlinear responses,all-optical methods are still in the exploration stages.We incorporate,to the best of our knowledge,the first experimental demonstration of feedback-based wavefront shaping techniques in atomically thin media to reveal and enhance the weak second harmonic generation of monolayer WS_(2).Phase tuning of the incident wavefront leads to the increase in the intensity of the second harmonic generated in the target regions up to an order of magnitude.We enhance the local nonlinear signal conversion from monolayer WS_(2)up to 41× using phase-only modulation.Furthermore,by introducing a shift in the transverse phase structure,we achieve observable second harmonic generation at the destructively interfering grain boundaries of polycrystalline monolayers.This method allows for all-optical tuning of transition metal dichalcogenides'nonlinear responses,opening up possibilities for dynamic signal routing and on-demand enhancement in nanoscale photonic systems.展开更多
Inspired by recent experimental results,the electronic and magnetic properties of sulfur-passivated ZnO clusters and zigzag nanoribbons have been studied using fi rst principles calculations in the framework of the lo...Inspired by recent experimental results,the electronic and magnetic properties of sulfur-passivated ZnO clusters and zigzag nanoribbons have been studied using fi rst principles calculations in the framework of the local spin density approximation.In the case of the ZnO nanoribbons,the sulfur atoms or thiol groups were attached in different ways to the zinc or oxygen atoms located at the edges,whereas in clusters,the sulfur atoms were set on the surface,mainly interacting with atoms with low-coordinate number.After an exhaustive atomic relaxation,we found that a magnetic moment emerges in zigzag nanoribbons both with and without sulfur-passivation on the edges.However,the magnitude of the magnetic moment is very sensitive to sulfur passivation.In particular,we found that when sulfur is attached to the zinc atoms in an alternating fashion along the ribbon edges,the magnetic moment is a maximum(1.4μB/unit cell).In the case of clusters,we found that the Zn_(15)O_(15) cluster exhibits a high spin moment of 5.5μB when capped with sulfur atoms.Our calculations indicate that sulfur-passivating of ZnO nanosystems could be responsible for recently observed ferromagnetic responses.展开更多
基金Gordon and Betty Moore FoundationU.S.Department of Energy(DE-SC0024676)+2 种基金National Geospatial-Intelligence Agency(HM04762010012)U.S.Department of Energy(DE-SC0023148)Air Force Office of Scientific Research(FA9550-23-1-0325).
文摘Two-dimensional transition metal dichalcogenides are of great interest for second harmonic generation due to their large second-order susceptibility χ^((2)),atomically thin structure,and relaxed phase-matching conditions.Such materials are also promising candidates for miniaturizing nonlinear optical devices for versatile applications in photon manipulation,quantum emission and sensing,and nanophotonic circuits.However,their strong second harmonic response is limited by nanometer-scale light-matter interaction and material impurities.Although there is considerable work toward engineering these materials for enhancing their nonlinear responses,all-optical methods are still in the exploration stages.We incorporate,to the best of our knowledge,the first experimental demonstration of feedback-based wavefront shaping techniques in atomically thin media to reveal and enhance the weak second harmonic generation of monolayer WS_(2).Phase tuning of the incident wavefront leads to the increase in the intensity of the second harmonic generated in the target regions up to an order of magnitude.We enhance the local nonlinear signal conversion from monolayer WS_(2)up to 41× using phase-only modulation.Furthermore,by introducing a shift in the transverse phase structure,we achieve observable second harmonic generation at the destructively interfering grain boundaries of polycrystalline monolayers.This method allows for all-optical tuning of transition metal dichalcogenides'nonlinear responses,opening up possibilities for dynamic signal routing and on-demand enhancement in nanoscale photonic systems.
基金This work was supported in part by CONACYT-México grants:56787(Laboratory for Nanoscience and Nanotechnology Research-LINAN),60218(FLU),45762(HT),45772(MT),58899-Inter American Collaboration(MT),2004-01-013/SALUD-CONACYT(MT)Fondo Mixto de San Luis Potosi63001 S-3908(MT)+1 种基金Fondo Mixto de San Luis Potosí63072 S-3909(HT)a PhD Scholarship(ARBM).
文摘Inspired by recent experimental results,the electronic and magnetic properties of sulfur-passivated ZnO clusters and zigzag nanoribbons have been studied using fi rst principles calculations in the framework of the local spin density approximation.In the case of the ZnO nanoribbons,the sulfur atoms or thiol groups were attached in different ways to the zinc or oxygen atoms located at the edges,whereas in clusters,the sulfur atoms were set on the surface,mainly interacting with atoms with low-coordinate number.After an exhaustive atomic relaxation,we found that a magnetic moment emerges in zigzag nanoribbons both with and without sulfur-passivation on the edges.However,the magnitude of the magnetic moment is very sensitive to sulfur passivation.In particular,we found that when sulfur is attached to the zinc atoms in an alternating fashion along the ribbon edges,the magnetic moment is a maximum(1.4μB/unit cell).In the case of clusters,we found that the Zn_(15)O_(15) cluster exhibits a high spin moment of 5.5μB when capped with sulfur atoms.Our calculations indicate that sulfur-passivating of ZnO nanosystems could be responsible for recently observed ferromagnetic responses.
