Photoinduced tunability of the reststrahlen band in4H−SiC

Abstract

Materials with a negative dielectric permittivity (e.g. metals) display high reflectance and can be shaped into nanoscale optical-resonators exhibiting extreme mode confinement, a central theme of nanophotonics. However, the ability to actively tune these effects remains elusive. By photoexciting free carriers in 4H-SiC, we induce dramatic changes in reflectance near the "Reststrahlen band" where the permittivity is negative due to charge oscillations of the polar optical phonons in the mid-infrared. We infer carrier-induced changes in the permittivity required

Ultralow-loss polaritons in isotopically pure boron nitride

“…However, advances in nanophotonics have produced ultrathin, so-called "flat" optical components that beget abrupt changes in these properties over distances significantly shorter than the free space wavelength. [1][2][3][4][5][6][7][8] While high optical losses still plague many approaches, 9 phonon polariton (PhP) materials have demonstrated long lifetimes for sub-diffractional modes [10][11][12][13] in comparison to plasmon-polariton-based nanophotonics. We experimentally observe a three-fold improvement in polariton lifetime through isotopic enrichment of hexagonal boron nitride (hBN).…”

Active tuning of surface phonon polariton resonances via carrier photoinjection

“…Off the array, the response is negative, indicating a lower reflectivity consistent with Reststrahlen-band softening. 37 For both nanostructure resonances and bulk SiC, a portion of the response was observed to recover exponentially in ~ 140 ps, after which the remainder of the signal persists for > 500 ps. Prior work has shown that the bulk carrier recombination lifetime is dominated by Shockley-Read-Hall processes with a lifetime of 900 ns.…”

“…The magnitude of the resonance shifts and the associated broadening of the SPhP resonances with increasing photoinjected carrier density are qualitatively reproduced by finitedifference time-domain (FDTD) simulations (Fig 3c). For the calculated spectra, the 4H-SiC dielectric function was taken from Spann et al 37 with the free-carrier damping time fixed at 12.5 fs. The experimental and calculated spectral shifts of the transverse dipole resonance with carrier concentration are provided in Fig.…”

Optical Nonlocality in Polar Dielectrics

“…A promising alternative in the midinfrared is surface phonon polariton (SPhP) light concentrators, which permit deep subwavelength light confinement by storing electromagnetic energy as vibrations of the crystal lattice [5][6][7]. Localization of SPhPs in user-defined resonators [8] allows for extremely small mode volumes [9,10] in highly tunable low-loss modes [11][12][13][14], with applications in sensing [15], nonlinear optics [16,17], and the creation of nanophotonic circuitry [18][19][20].…”