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RESEARCH PRODUCT

Femtosecond exciton dynamics in WSe2 optical waveguides

Yinming ShaoB. KimDimitri BasovGuangxin NiMichael M. FoglerMichal LipsonPeter KissinNorman Nan ShiAndrew J. MillisXiaolin ZhuSang Hoon ChaeAaron SternbachP SchuckDaniel RhodesRichard D. AverittSimone LatiniZhiyuan SunNanfang YuUmberto De GiovanniniAngel RubioJames HoneLin XiongHannes Hübener

subject

Materials scienceTerahertz radiationExcitonScienceGeneral Physics and AstronomyPhysics::Optics02 engineering and technology01 natural sciencesWaveguide (optics)General Biochemistry Genetics and Molecular BiologySettore FIS/03 - Fisica Della Materiasymbols.namesakeCondensed Matter::Materials Science0103 physical sciencesPhysics::Atomic and Molecular Clusters010306 general physicslcsh:ScienceMultidisciplinarybusiness.industryQGeneral Chemistry021001 nanoscience & nanotechnology2D materialsPhotoexcitationSemiconductorStark effectFemtosecondsymbolsOptoelectronicslcsh:Q0210 nano-technologybusinessUltrashort pulse

description

Van-der Waals (vdW) atomically layered crystals can act as optical waveguides over a broad range of the electromagnetic spectrum ranging from Terahertz to visible. Unlike common Si-based waveguides, vdW semiconductors host strong excitonic resonances that may be controlled using non-thermal stimuli including electrostatic gating and photoexcitation. Here, we utilize waveguide modes to examine photo-induced changes of excitons in the prototypical vdW semiconductor, WSe2, prompted by femtosecond light pulses. Using time-resolved scanning near-field optical microscopy we visualize the electric field profiles of waveguide modes in real space and time and extract the temporal evolution of the optical constants following femtosecond photoexcitation. By monitoring the phase velocity of the waveguide modes, we detect incoherent A-exciton bleaching along with a coherent optical Stark shift in WSe2. The authors use time-resolved scanning near-field optical microscopy to probe the ultrafast excitonic processes and their impact on waveguide operation in transition metal dichalcogenide crystals. They observe significant modulation of the complex index by monitoring waveguide modes on the fs time scale, and identify both coherent and incoherent manipulations of WSe2 excitonic resonances.

yearjournalcountryeditionlanguage
2020-07-01Nature Communications
10.1038/s41467-020-17335-whttp://link.springer.com/article/10.1038/s41467-020-17335-w