Plasmonic Nanoantennas for Broad-Band Enhancement of Two-Photon Emission from Semiconductors

Abstract

We demonstrate experimentally and theoretically a broad-band enhancement of the spontaneous two-photon emission from AlGaAs at room temperature by plasmonic nanoantenna arrays fabricated on the semiconductor surface. Plasmonic structures with inherently low quality factors but very small effective volumes are shown to be optimal. A 20-fold enhancement was achieved for the entire antenna array, corresponding to an enhancement of nearly 3 orders of magnitude for charge carriers emitting at the near field of a plasmonic antenna.KEYWORDS Semiconductors, two-photon emission, nanoparticles, plasmonic enhancement O ver the past decade, a growing interest has been focused on exploiting the tight confinement of the electromagnetic field achievable in the vicinity of a metal-dielectric boundary, commonly referred to as surface plasmon polariton (SPP), for enhancing the efficiency of spontaneous emission in semiconductors, 1-3 and it has been shown that such enhancement is highly significant for very inefficient emitters. 4 These endeavors follow the success of using SPPs for the enhancement of nonlinear phenomena, including the surface enhancement of Raman scattering by many orders of magnitude, 5 surface-enhanced second-harmonic generation, 6 and the recent demonstration of high-harmonic generation by coupling to bow-tie nanoantennas. 7 It was also shown that SPPs preserve many key quantum properties of the photons used to excite them, including entanglement, 8,9 and the quantization theory of surface plasmon fields was developed 10 and experimentally demonstrated, 11 allowing an array of new applications in quantum information processing. Two-photon emission (TPE) is a nonlinear process with unique quantum properties, important in different realms of science. TPE from a semiconductor results from electronhole recombination with the simultaneous emission of two photons. Semiconductor TPE was recently observed 12 and theoretically analyzed, 13 and current-induced two-photon transparency was demonstrated, 14 paving the way for the realization of room-temperature miniature devices, including semiconductor two-photon lasers 15 and photon pair sources. 16 However, TPE is an inherently weak second-order process, and therefore enhancing mechanisms could significantly widen the range of its applications. Since the emission spectrum of spontaneous TPE is very wide band due to the large energy uncertainty of the virtual state, regular dielectric optical cavities with a very high qualityfactor, Q, and thus very narrow bandwidth 17 may enhance emission at specific wavelengths; 18 however, they are unable to enhance the broad spectrum of TPE. Plasmonic cavities, on the other hand, enhancing the field by significantly reducing the mode volume at low Q, 19 are optimal.Here we report the first experimental observation of plasmon-enhanced spontaneous TPE from semiconductors, by coupling the emission to bow-tie nanoantenna arrays, having efficient radiative coupling of plasmons to far-field light. 20 The broad band TPE from AlGaA...

High Order Gap Modes of Film-Coupled Nanospheres

“…[3][4] The enhanced field resulting from surface plasmon resonance has been utilized for surface enhancing spectroscopy such as surface-enhanced Raman scattering (SERS), [5][6][7] refractive index monitoring, [8][9][10] and manipulation of light-matter interaction. [11][12][13][14][15][16][17][18][19][20] In addition to intrinsic properties of constituent metals, the optical features of plasmonic structures usually depend on their morphology. Therefore, considerable efforts have been devoted to developing fabrication/synthesis methods [21][22][23][24][25][26][27] to obtain new single structures with the desired optical properties.…”

Applications of quantum photonics for communications and metrology

“…Spontaneous and singly-stimulated two-photon emission in bulk GaAs and in electrically-driven quantum wells were observed at room temperature ( Fig. 1) 25,26 and enhanced two-photon emission was achieved by nano-plasmonic structures 27 . We proposed the phenomenon of semiconductor two-photon emission as an electrically-driven room-temperature source of energy-entangled photons, much more efficient than down-conversion schemes, and without the need for phasematching 28 .…”

Plasmonic spiderweb nanoantenna surface for broadband hotspot generation

“…However, in many emerging practical applications, such as thin-film solar cells [3,4], single molecule spectroscopy [5,6], single molecule detection [5], nonlinear optics [7,8], near-field imaging [9], pulse shaping [10], optical information processing [11], and light bending [12], broadband plasmonic structures are essential. There have been many attempts to fill this gap, and some broadband plasmonic structures have been demonstrated in the form of single antenna [8,13], plasmonic surfaces [14,15], multilayer structures [4], metamaterials [16][17][18], metallodielectric composites [17], and particle suspensions [19].…”

“…In many applications such as high harmonic generation [8] surface-enhanced spectroscopy techniques [24], and spontaneous two photon emission [7], a broadband hotspot is crucial. There are some structures able to produce broadband hotspots [8,[13][14][15]21], however, these structures do not produce a polarization-independent broadband hotspot in a close-packed geometric form.…”