Tuning of Two-Dimensional Plasmon–Exciton Coupling in Full Parameter Space: A Polaritonic Non-Hermitian System

Sang, Yungang; Wang, Chun Yuan; Raja, Soniya S.; Cheng, Chang‐Wei; Zhang, Xin Quan; Ahn, Hyeyoung; Shih, Chih Kang; Lee, Yi Hsien; Shi, Jianzhong; Gwo, Shangjr

doi:10.1021/acs.nanolett.1c00198

Cited by 25 publications

(15 citation statements)

References 49 publications

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“…On the other hand, the linewidths of UPB and LPB obtained by superposition of two Lorentzian line shapes illustrate a crossover behavior in Figure 2f, unambiguously confirming the presence of polariton states. [ 37 ] In the case of single WS 2 ‐NGs structure, a decreased Rabi splitting of 42 meV can be extracted from reflectance spectrum (Section S2, Supporting Information) and it coincides well with the expected scaling of Rabi splitting with number of emission layers

{\Omega _{\rm{R}}} \propto \sqrt N

, [ 30 ] where N denotes the layer number of WS 2 in this case.…”

Section: Resultssupporting

confidence: 65%

Strong Linearly Polarized Emission from Monolayer WS₂ Coupled with Plasmonic Nanocavity Array

Huang

Guo

et al. 2022

Advanced Optical Materials

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As an indispensable component of optoelectronic system, an on‐chip light source with well‐defined polarization is desirable in optical communication, signal processing and display applications. The emerging atomically thin transition metal dichalcogenides (TMDCs), due to their high quantum yield and robust valley coherence, provide an unprecedented platform to realize the high‐efficient linearly polarized light emission. Although the valley‐related optical selection rules suggest that valley coherence should be possible, extreme conditions such as cryogenic temperatures are required, which is a long‐term challenge for their practical applications. In this paper, the strongly enhanced linearly polarized emission is realized by integrating WS2 monolayers with a delicate designed plasmonic nanocavity. It is demonstrated that strong plasmon–exciton coupling gives rise to the plasmon–exciton polariton. The polariton valley coherence results in a linear polarization up to 0.32 at room temperature and contributes to 52% of the total linear polarization. Enhancement of linear polarization through polariton valley coherence can be understood as the consequence of the extra relaxation channel introduced by its plasmonic counterpart. The potential of 2D TMDC‐plasmon hybrid structure appears to be high and of significant technological interest, as well as inspires new perspectives on quantum manipulations in 2D solid‐state systems.

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{\Omega _{\rm{R}}} \propto \sqrt N

, [ 30 ] where N denotes the layer number of WS 2 in this case.…”

Section: Resultssupporting

confidence: 65%

Strong Linearly Polarized Emission from Monolayer WS₂ Coupled with Plasmonic Nanocavity Array

Huang

Guo

et al. 2022

Advanced Optical Materials

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“…Figure 4a shows the reflection spectra of Ag ND–WS 2 samples with different dielectric interlayer thicknesses. The spectral dip (i.e., SW) in the reflection decreases for thicker alumina (Al 2 O 3 ) interlayers since the coupling strength decreases as the field overlap between plasmons and excitons is reduced 63 . Figure 4b further records the differential reflection ( ) signals of these Ag ND–WS 2 samples at t = 100 fs under 2.0 µJ cm −2 resonant excitation (complete reflection spectral signals can be accessed in Supplementary Note 10 ), where stronger positive photoinduced absorption (PA) and negative photoinduced bleaching (PB) signals are observed for thinner Al 2 O 3 interlayers.…”

Section: Resultsmentioning

confidence: 99%

Interacting plexcitons for designed ultrafast optical nonlinearity in a monolayer semiconductor

et al. 2022

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Searching for ideal materials with strong effective optical nonlinear responses is a long-term task enabling remarkable breakthroughs in contemporary quantum and nonlinear optics. Polaritons, hybridized light-matter quasiparticles, are an appealing candidate to realize such nonlinearities. Here, we explore a class of peculiar polaritons, named plasmon–exciton polaritons (plexcitons), in a hybrid system composed of silver nanodisk arrays and monolayer tungsten-disulfide (WS2), which shows giant room-temperature nonlinearity due to their deep-subwavelength localized nature. Specifically, comprehensive ultrafast pump–probe measurements reveal that plexciton nonlinearity is dominated by the saturation and higher-order excitation-induced dephasing interactions, rather than the well-known exchange interaction in traditional microcavity polaritons. Furthermore, we demonstrate this giant nonlinearity can be exploited to manipulate the ultrafast nonlinear absorption properties of the solid-state system. Our findings suggest that plexcitons are intrinsically strongly interacting, thereby pioneering new horizons for practical implementations such as energy-efficient ultrafast all-optical switching and information processing.

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“…[ 37 ] There are many other reports of η = 4–9% in the TMDCs. [ 4,38–44 ] All of these reports couple to the lowest energy A or B excitons. By targeting the larger oscillator strength of the C exciton, we achieve ultrastrong coupling at room temperature in the TMDCs.…”

Section: Discussionmentioning

confidence: 99%

Ultrastrong Coupling of Band‐Nested Excitons in Few‐Layer Molybdenum Disulphide

Rose

Aubry

Zhang

et al. 2022

Advanced Optical Materials

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able in organic systems, with typical Rabi splitting values of ≲150 meV or ≲6% of the exciton energy. In organic systems, Rabi splitting of >10%, which is in the ultrastrong coupling regime, is common. [11][12][13][14][15][16][17][18] In the ultrastrong coupling regime, coupling interactions are expected to be more efficient and emergent quantum coherent phenomena, such as ground-state virtual photons and entangled pairs, are predicted to exist even at room temperature or without resolvable Rabi splitting due to broad resonators. [19,20] As such, it is desirable to achieve this regime in a CMOS-compatible system like the TMDCs. In this paper, we exploit the large oscillator strength of the C exciton in few-layer molybdenum disulphide (FL-MoS 2 ) to achieve ultrastrong coupling at room temperature. The C Exciton of 2D TMDCs has Unique PropertiesThe C exciton of the 2D TMDCs does not arise from the same type of band structure features as the more commonly studied A and B excitons near the band edge, and thus, it has unique behavior. The A and B exciton absorption features in FL-MoS 2 are labeled in Figure 1a. These excitons correspond to transitions between the conduction band minimum and the spinorbit-split valence band maxima at the K point in Figure 1b. The next prominent absorption feature is the C exciton, which has significantly larger oscillator strength than the A or B, as seen by comparing the Lorentzian fits in Figure 1a.Interestingly, the C exciton does not arise from transitions between two opposite concavity parabolic bands, but rather between regions of parallel bands, referred to as nested bands, shown by the shaded region in Figure 1b. [21] The C exciton oscillator strength is large because of this parallel band region of k-space, and thus, the density of states at the C exciton transition energy is large.An unusual consequence of the nested bands is that C exciton carriers are expected to spontaneously self-separate in momentum space [22][23][24] and exhibit slowed hot carrier cooling relative to the A and B excitons. [23] This slowed cooling has been seen by Wang et al. [23] and ourselves [25] in ultrafast spectroscopic studies. Typically, photoexcited hot carriers in semiconductor devices thermalize to the band edges on femtosecond timescales before reaching the contacts. Photovoltage is therefore limited to the bandgap potential. In contrast, for hot carrier devices, The 2D transition-metal dichalcogenides (2D TMDCs) are an intriguing platform for studying strong light-matter interactions because they combine the electronic properties of conventional semiconductors with the optical resonances found in organic systems. However, the coupling strengths demonstrated in strong exciton-polariton coupling in the 2D TMDCs remain much lower than those found in organic systems. In this paper, a new approach is taken by utilizing the large oscillator strength of the above-band gap C exciton in few-layer molybdenum disulphide (FL-MoS 2 ). A k-space Rabi splitting of 293 meV is shown when coupling FL-MoS 2 C...

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Tuning of Two-Dimensional Plasmon–Exciton Coupling in Full Parameter Space: A Polaritonic Non-Hermitian System

Cited by 25 publications

References 49 publications

Strong Linearly Polarized Emission from Monolayer WS₂ Coupled with Plasmonic Nanocavity Array

Strong Linearly Polarized Emission from Monolayer WS₂ Coupled with Plasmonic Nanocavity Array

Interacting plexcitons for designed ultrafast optical nonlinearity in a monolayer semiconductor

Ultrastrong Coupling of Band‐Nested Excitons in Few‐Layer Molybdenum Disulphide

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Tuning of Two-Dimensional Plasmon–Exciton Coupling in Full Parameter Space: A Polaritonic Non-Hermitian System

Cited by 25 publications

References 49 publications

Strong Linearly Polarized Emission from Monolayer WS2 Coupled with Plasmonic Nanocavity Array

Strong Linearly Polarized Emission from Monolayer WS2 Coupled with Plasmonic Nanocavity Array

Interacting plexcitons for designed ultrafast optical nonlinearity in a monolayer semiconductor

Ultrastrong Coupling of Band‐Nested Excitons in Few‐Layer Molybdenum Disulphide

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Strong Linearly Polarized Emission from Monolayer WS₂ Coupled with Plasmonic Nanocavity Array

Strong Linearly Polarized Emission from Monolayer WS₂ Coupled with Plasmonic Nanocavity Array