Femtosecond exciton dynamics in WSe2 optical waveguides

Sternbach, Aaron; Latini, Simone; Chae, Sanghoon; Hübener, Hannes; Giovannini, Umberto De; Shao, Yinming; Xiong, Lin; Sun, Zhiyuan; Shi, Norman Nan; Kissin, Peter; Ni, Guangxin; Rhodes, Daniel; Kim, Brian; Yu, Nanfang; Millis, Andrew J.; Fogler, M. M.; Schuck, P. James; Lipson, Michal; Zhu, Xiaoyang; Hone, James; Averitt, R. D.; Rubio, Ángel; Basov, D. N.

doi:10.1038/s41467-020-17335-w

Cited by 36 publications

(48 citation statements)

References 32 publications

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“…We note that polariton visualization becomes increasingly difficult the slower it propagates, as this entails that for a certain illumination bandwidth a large range of k vectors are simultaneously excited, therefore leading to self‐interference effects and limited apparent propagation. [ 29 ] For the PhP [100] modes manifested in the ultranarrow RB 3 (ν LO − ν TO ≈ 0.72 THz), even with our relatively narrowband FEL excitation (Figure 1b), a range of polaritons spanning a finite k window can be excited. This particularly applies to the PhP [100] polaritons on the thinnest flake with d = 53 nm, wherein no reliable polariton dispersion data could be extracted as only a single fringe was observed.…”

Section: Figurementioning

confidence: 99%

Nanoscale‐Confined Terahertz Polaritons in a van der Waals Crystal

et al. 2020

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Electromagnetic field confinement is crucial for nanophotonic technologies, since it allows for enhancing light–matter interactions, thus enabling light manipulation in deep sub‐wavelength scales. In the terahertz (THz) spectral range, radiation confinement is conventionally achieved with specially designed metallic structures—such as antennas or nanoslits—with large footprints due to the rather long wavelengths of THz radiation. In this context, phonon polaritons—light coupled to lattice vibrations—in van der Waals (vdW) crystals have emerged as a promising solution for controlling light beyond the diffraction limit, as they feature extreme field confinements and low optical losses. However, experimental demonstration of nanoscale‐confined phonon polaritons at THz frequencies has so far remained elusive. Here, it is provided by employing scattering‐type scanning near‐field optical microscopy combined with a free‐electron laser to reveal a range of low‐loss polaritonic excitations at frequencies from 8 to 12 THz in the vdW semiconductor α‐MoO3. In this study, THz polaritons are visualized with: i) in‐plane hyperbolic dispersion, ii) extreme nanoscale field confinement (below λo ⁄75), and iii) long polariton lifetimes, with a lower limit of >2 ps.

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Section: Figurementioning

confidence: 99%

Nanoscale‐Confined Terahertz Polaritons in a van der Waals Crystal

et al. 2020

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“…Recent advances in time-resolved SNOM also allowed the polariton's group velocity to be extracted from the interference of scattered polaritons with different time delays (35,53,54).…”

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confidence: 99%

Spatiotemporal imaging of 2D polariton wave packet dynamics using free electrons

Kurman

Dahan

Sheinfux

et al. 2021

Science

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Coherent optical excitations in two-dimensional (2D) materials, 2D polaritons, can generate a plethora of optical phenomena that arise from the extraordinary dispersion relations that do not exist in regular materials. Probing of the dynamical phenomena of 2D polaritons requires simultaneous spatial and temporal imaging capabilities and could reveal unknown coherent optical phenomena in 2D materials. Here, we present a spatiotemporal measurement of 2D wave packet dynamics, from its formation to its decay, using an ultrafast transmission electron microscope driven by femtosecond midinfrared pulses. The ability to coherently excite phonon-polariton wave packets and probe their evolution in a nondestructive manner reveals intriguing dispersion-dependent dynamics that includes splitting of multibranch wave packets and, unexpectedly, wave packet deceleration and acceleration. Having access to the full spatiotemporal dynamics of 2D wave packets can be used to illuminate puzzles in topological polaritons and discover exotic nonlinear optical phenomena in 2D materials.

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“…The larger λ obs2 can be assigned to the air/ITO mode ( k = n ITO k 0 ), which is same as the previous report. [ 15,24 ] Spatial mode periodicity for λ E ranging from 530 to 560 nm is compared with the theoretical waveguide mode in Figure 2g,h. The λ obs is obtained by the FFT spectra as shown in Table S1 (Supporting Information), which proved the variation of the photonic mode relating to the photoexcitation wavelength both in experimental and theoretical calculations.…”

Section: Resultsmentioning

confidence: 99%

“…), and even the Moiré superlattices observation in twisted bilayer graphene were revealed. [ 13–16 ] PEEM is a wide‐field microscopy technique, which uses surface photoelectrons to image the photonic modes, especially for the surface plasmon polariton (SPP), e.g., the nanoplasmonic vortices, plasmonic topological state, and SPP propagation in a nanocircuit. [ 8,17–21 ] However, the investigation on photonic mode of semiconductor microcavities in real space is still limited at moment, especially, for the widely interested perovskite microcavity.…”

Section: Introductionmentioning

confidence: 99%

Imaging and Controlling Photonic Modes in Perovskite Microcavities

Liu

et al. 2021

Advanced Materials

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Perovskite microcavities have excellent photophysical properties for integrated optoelectronic devices, such as nanolasers. Imaging and controlling the photonic modes within the cavity are fundamentally important to understand and develop applications. Here, photoemission electron microscopy (PEEM) is used to image the photonic modes within optical microcavities with a nanometer‐scale spatial resolution. From a CsPbBr3 microcavity, hybrid mode patterns are observed. Spatial frequency spectrum analysis on the patterns uncovers the characteristic cavity modes, which are modeled with transverse magnetic (TM) and transverse electric (TE) waves, and assigned to exciton–polariton modes. Based on this understanding, the light focus in a designed microcavity is imaged in real space and controlled by the light field polarization. The study confirms that the cavity modes in perovskites can be effectively observed by the PEEM technique under resonant excitation, which, in turn, promotes the design of optoelectronic devices based on perovskite microcavities.

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Femtosecond exciton dynamics in WSe2 optical waveguides

Cited by 36 publications

References 32 publications

Nanoscale‐Confined Terahertz Polaritons in a van der Waals Crystal

Nanoscale‐Confined Terahertz Polaritons in a van der Waals Crystal

Spatiotemporal imaging of 2D polariton wave packet dynamics using free electrons

Imaging and Controlling Photonic Modes in Perovskite Microcavities

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