Enhanced emission from ultra-thin long wavelength infrared superlattices on epitaxial plasmonic materials

Abstract

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 ...

All-Epitaxial Integration of Long-Wavelength Infrared Plasmonic Materials and Detectors for Enhanced Responsivity

“…These “designer metals”, when epitaxially grown, offer control over the spectral range of plasmonic behavior, − as well as control over the dimensions and doping profile of the plasmonic layers with the atomic precision of MBE. Perhaps most importantly these heavily doped semiconductors offer the potential for monolithic integration of plasmonic materials with not only mid-IR quantum engineered emitters, but as we show here, optoelectronic device architectures . We numerically simulate and experimentally demonstrate significant absorption enhancement in thin LWIR detectors, resulting in detector efficiencies commensurate with those of much thicker detectors found in the literature.…”

Subdiffraction Limited Photonic Funneling of Light

“…Experimentally, such a system could be realized by either placing the funnel tip in the near‐field proximity of a mid‐IR source, or alternatively, by integrating such a source directly into the semiconductor material during epitaxial growth. [ 34 ] Once again, we compare the performance of the hyperbolic funnels with cross sections realized in our experiments to the performance of funnels with identical cross sections but with lossless InP cores. The enhancement of light extraction by the funnels with the HMM cores, as well as the typical Purcell enhancement associated with these structures, is summarized in Figure .…”

Enhanced Room Temperature Infrared LEDs using Monolithically Integrated Plasmonic Materials

“…To elucidate this effect, we modeled our system using a Dyadic Green's function formalism, incorporated into a transfer matrix method solver [25][26][27], positioning our emitter at the five QD layer positions. These calculations provide us with the position-and wavelength-dependent Purcell enhancement (P(λ)), as well as the Purcell-corrected Poynting flux representing the total energy emitted by the point dipole to the far field (S z (λ)), shown in Fig.…”