Experimental confirmation of long hyperbolic polariton lifetimes in monoisotopic (10B) hexagonal boron nitride at room temperature
Georges Pavlidis, Jeffrey Schwartz, Joseph Matson, Thomas Folland, Song Liu, James Edgar, Joshua Caldwell, Andrea Centrone
Hyperbolic phonon polaritons (HPhPs) enable arbitrarily high confinements, low losses, and directional propagation – providing opportunities from hyperlensing to flat optics, and other advanced nanophotonics applications. In this work, two near-field techniques: photothermal induced resonance (PTIR) and scattering-type scanning near-field optical microscopy (s SNOM) are used to map infrared HPhPs propagating in large (up to 120 μm × 250 μm) near-monoisotopic (≈ 99.22 % 10B) hBN flakes. Fourier analyses (0.13 µm-1 resolution) of ≈ 40 µm wide real space PTIR images enables precise measurements of HPhP lifetimes up to ≈ 4.2 ps and propagation lengths up to ≈ 25 µm for the first-order HPhP branch and, remarkably, up to ≈ 17 µm for the second-order branch. Record breaking experimental figures of merit (FOM), i.e., the Q of the polaritons in Fourier space up to ≈ 90 (an 8 fold improvement with respect to natural hBN) are measured in ≈ 99.22 % 10B hBN, confirming, at last, previous theoretically predicted values. Importantly, the comparison of PTIR and s-SNOM data show that the incidence angle of light, with respect to both the sample plane and the flake edge, needs to be taken into account to extract correctly the dispersion relation from near-field polaritons maps. This study establishes guidelines to compare directly near-field data obtained with different experimental methods and boundary conditions. Overall, the measurements and data analyses employed here elucidate details pertaining to polaritons propagation in isotopically enriched hBN and pave the way for developing high-performance HPhP based devices.
, Schwartz, J.
, Matson, J.
, Folland, T.
, Liu, S.
, Edgar, J.
, CALDWELL, J.
and Centrone, A.
Experimental confirmation of long hyperbolic polariton lifetimes in monoisotopic (10B) hexagonal boron nitride at room temperature, APL Materials, [online], https://doi.org/10.1063/5.0061941, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=932855
(Accessed August 17, 2022)