Research ArticleChemistry

Nonlinear infrared polaritonic interaction between cavities mediated by molecular vibrations at ultrafast time scale

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Science Advances  07 May 2021:
Vol. 7, no. 19, eabf6397
DOI: 10.1126/sciadv.abf6397
  • Fig. 1 Key idea of intercavity nonlinear interactions between polaritons.

    (A) Illustration of a coupled cavity and 2D IR pulse sequence. The key to enable intercavity nonlinear interaction is to have anharmonic molecules (enlarged) in the shared volume between cavities. (B) A proposed mechanism of coupling between cavities. When a photon enters into cavity A, it hops to cavity B and exits from there (cavity A path). The reversed direction (cavity B path) could happen too. (C) Scanning electron microscopy of checkerboard-patterned cavity mirror. (D) FTIR of the dual cavity modes (1970 and 2000 cm−1). (E) Energy diagram of polariton modes formed by the coupling of W(CO)6 with the coupled cavity. (F to I) Experimental and simulated linear IR transmission of polaritons. (F and G) Polariton tranmission spectra in a regular cavity detuned to match the resonance of cavities A and B, which can be well fitted by model 1. (H) Experimental polariton tranmission spectra of the coupled cavity and the summed spectra of (F) and (G). (I) Experimental and simulated linear IR of polaritons in the coupled cavity. Using model 2 (see the main text and section S2.2 for details), the experimental spectra can be well simulated. Additional minor polariton peaks appear due to delocalization to the neighboring modes. (J) Transmission image of coupled cavity polariton system where LP1/UP1 states (cavity A polaritons) locate at the top part, while the LP2/UP2 states (cavity B polaritons) locate at the bottom part. The spatial separation between cavity A and B polaritons is 47 μm, close to the pattern size of 50 μm. There is a substantial overlapping area between the two modes as a result of mode delocalization, which is highlighted as an orange area on the right panel. See detailed experimental setup in section S3.7.

  • Fig. 2 2D IR spectra to show intercavity nonlinear interactions between polaritons.

    (A) 2D IR of W(CO)6/hexane in coupled dual cavity. Cross-peaks between polaritons from different cavities are observed (in shaded green areas). The 2D IR peaks that are solely from cavity A are at the corner of blue square and that of cavity B are at the corners of black square. The spectrum was taken with the IR incidence angle (the angle between IR beam and the cavity plane normal, Φ, as shown in fig. S1) to be 11.3°. (B) Pump spectral cuts of 2D IR in (A) at ωpump = ωUP1 (blue), ωUP2 (red), ωLP1 (yellow), and ωLP2 (purple) also show cross-peak features. The green and black arrows in (B) to (E) highlight the cross-peaks due to intercavity nonlinear interactions. (C and D) Experimental (blue dots) and simulated (yellow) spectral cut at ωpump = ωUP1 and at ωpump = ωUP2 and the corresponding simulated contributions from cavities A (purple) and B (green). (E) Experimental (blue dots) spectral cut at ωpump = ωUP1 and simulated cut spectrum with nonlinearity off (sky blue), with delocalization off (red), and delocalization and molecular nonlinearity together (yellow). (F) 2D IR dynamics at ωpump = ωUP1.

  • Fig. 3 2D IR spectrum of dual cavity polaritons at small Rabi splitting.

    (A) 2D IR of W(CO)6/hexane in coupled dual cavity with 26 mM molecular concentration; the 2D IR peaks that are solely from cavity A are at the corner of blue square and that of cavity B are at the corners of black square. (B) Pump spectral cuts of 2D IR at ωpump = ωUP1 and ωLP1 (blue/red traces for polariton system with 26/40 mM molecular concentration, both are at t2 = 20 ps) confirm the decrease of cross-peaks with smaller molecular concentration. All data were collected with the incidence IR beam to be 11.3°. (C) Schematic illustration of the intercavity coupling enabled/disabled in coupled cavity systems with high/low molecular concentration (top/bottom), |0>, |1>, |2 > are the ground, first, and second excited states of the reservoir modes; gray levels indicate the modes are optically dark. (D) Percentage of excited vib-B among the total excited vibrational modes in cavity A as a function of molecular concentration, extracted from the spectral fitting results.

Supplementary Materials

  • Supplementary Materials

    Nonlinear infrared polaritonic interaction between cavities mediated by molecular vibrations at ultrafast time scale

    Bo Xiang, Jiaxi Wang, Zimo Yang, Wei Xiong

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    This PDF file includes:

    • Experimental Methods
    • Theory for Intercavity Polariton-Polariton Interaction
    • Supplementary Data
    • Figs. S1 to S10
    • Tables S1 to S4

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