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Amplitude and phase-resolved nano-spectral imaging of surface phonon polaritons in hexagonal boron nitride



Samuel Berweger, Shi Zhiwen, Hans A. Bechtel, Sun Yinghui, Zeng Bo, Jin Chenhao, Chang Henry, Michael C. Martin, Markus B. Raschke, Feng Wang


Phonon polaritons are quasiparticles resulting from strong coupling of photons with optical phonons. Excitation and control of these quasiparticles in 2D materials offer the opportunity to confine and transport light at the nanoscale. Here, we image the surface phonon polariton (SPhP) spectral response in thin hexagonal boron nitride (HBN) crystals as a representative 2D material using amplitufe-and phase-resolved near-field interferometry with broadband mid-IR synchrotron radiation. The large spectral bandwidth enables the simultaneous measurement of both out-of-plane (780cm-1) and in-plane (1370 cm-1) hBN phonon modes. In contrast to the strong and dispersive in-plane mode, the out-of-plane mode SPhP response is weak. Measurements of the SPhP wavelength reveal a proportional dependence on sample thickness for thin hBN flakes, which can be understood by a general model describing two-dimensional polariton excitation in ultrathin materials.
Nano Letters


Surface phonon polariton, boron nitride, near-field spectroscopy, synchrotron infrared nano-spectroscopy (SINS)


Berweger, S. , Zhiwen, S. , Bechtel, H. , Yinghui, S. , Bo, Z. , Chenhao, J. , Henry, C. , Martin, M. , Raschke, M. and Wang, F. (2015), Amplitude and phase-resolved nano-spectral imaging of surface phonon polaritons in hexagonal boron nitride, Nano Letters, [online],, (Accessed July 22, 2024)


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Created June 8, 2015, Updated February 9, 2023