We demonstrate coupling to and control over the broadening and dispersion of a mid-infrared leaky mode, known as the Berreman mode, in samples with different dielectric environments. We fabricate subwavelength films of AlN, a mid-infrared epsilon-near-zero material that supports the Berreman mode, on materials with a weakly negative permittivity, strongly negative permittivity, and positive permittivity. Additionally, we incorporate ultra-thin AlN layers into a GaN/AlN heterostructure, engineering the dielectric environment above and below the AlN. In each of the samples, coupling to the Berreman mode is observed in angle-dependent reflection measurements at wavelengths near the longitudinal optical phonon energy. The measured dispersion of the Berreman mode agrees well with numerical modes. Differences in the dispersion and broadening for the different materials is quantified, including a 13 cm-1 red-shift in the energy of the Berreman mode for the heterostructure sample.
Molecular beam epitaxy allows for the monolithic integration of wavelength-flexible epitaxial infrared plasmonic materials with quantum-engineered infrared optoelectronic active regions. We experimentally demonstrate a six-fold enhancement in photoluminescence from ultra-thin (total thickness λ o /32) long wavelength infrared (LWIR) superlattices grown on highly doped semiconductor 'designer metal' virtual substrates when compared to the same superlattice grown on an undoped virtual substrate. Analytical and numerical models of the emission process via a Dyadic Green's function formalism are in agreement with experimental results and relate the observed enhancement of emission to a combination of Purcell enhancement due to surface plasmon modes as well as directionality enhancement due to cavitysubstrate-emitter interaction. The results presented provide a potential path towards efficient, ultra-subwavelength LWIR emitter devices, as well as a monolithic epitaxial architecture offering the opportunity to investigate the ultimate limits of light-matter interaction in coupled plasmonic/optoelectronic materials.The field of plasmonics centers around the generation and manipulation of hybrid electromagnetic/charge density waves supported at metal/dielectric interfaces 1 . Plasmonics' revival as a field of intense scientific interest, approximately two decades ago 2 , promised a litany of transformational advances in optics, sensing, and optoelectronics 3 . The list of much-heralded applications included, but was not limited to, on-chip sub-diffraction limited waveguiding 4,5 , higher efficiency photovoltaics 6,7 , sub-diffraction-limited lasers 8-10 , ultra-efficient emitters 11,12 , and enhanced sensitivity sensor systems [13][14][15][16][17] . However, the promised efficiency gains associated with plasmonic enhancement have largely been offset by the intrinsic losses of plasmonic materials 18 , especially in the already high optical quality semiconductor platforms that have benefited from decades of research and development investment from the imaging, sensing, and telecom industries. The mid-IR, however, does not suffer from the affliction of extremely efficient emitters; quite the opposite, in fact. At these long wavelengths, a host of non-radiative recombination mechanisms (Shockley Read Hall, Auger, phonon-assisted, trap-assisted tunneling, etc) 19-23 conspire to severely limit radiative efficiency, with ever more pronounced effect as the wavelength of emission increases. The inherently low efficiency of mid-IR sources, though, offers very real room for improvement, which can potentially be realized with plasmonic materials engineered specifically for the mid-IR.While the noble metals (Au, Ag, etc) are the plasmonic materials of choice at visible and near-IR wavelengths, the large negative real permittivity of the noble metals at longer wavelengths results in optical properties more closely resembling those of perfect electrical conductors (PECs) than plasmonic materials 24 . The PEC-like nature of traditional ...
Remarkable systems have been reported recently using the polylithic integration of semiconductor optoelectronic devices and plasmonic materials exhibiting epsilon-near-zero (ENZ) and negative permittivity. In traditional noble metals, the ENZ and plasmonic response is achieved near the metal plasma frequency, limiting plasmonic optoelectronic device design flexibility. Here, we leverage an all-epitaxial approach to monolithically and seamlessly integrate designer plasmonic materials into a quantum dot light emitting diode, leading to a 5.6 × enhancement over an otherwise identical non-plasmonic control sample. The device presented exhibits optical powers comparable, and temperature performance far superior, to commercially available devices.
We have observed directional spontaneous emission of rhodamine 6G dye deposited on top of a silver grating and found that its angular distribution patterns were very different in TE and TM polarizations. The latter was related to the dispersion curves determined based on the polarized reflection spectra measured at multiple incidence angles. The most intriguing finding of this Letter was a resonance, which was coupled with TE-polarized light and determined the characteristic double-crescent patterns in the TE-polarized spontaneous emission. This observation, as well as nearly similar resonance observed in TM polarization, was tentatively explained in terms of leaky waveguide modes supported by a film of dye-doped polymer.
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