Hybrid cavity-antenna systems for quantum optics outside the cryostat?

Abstract

Hybrid cavity-antenna systems have been proposed to combine the sub-wavelength light confinement of plasmonic antennas with microcavity quality factors Q. Here, we examine what confinement and Q can be reached in these hybrid systems, and we address their merits for various applications in classical and quantum optics. Specifically, we investigate their applicability for quantum-optical applications at noncryogenic temperatures. To this end we first derive design rules for hybrid resonances from a simple analytical model. These rules are benchmarked against full-wave simulations of hybrids composed of state-of-the-art nanobeam cavities and plasmonic-dimer gap antennas. We find that hybrids can outperform the plasmonic and cavity constituents in terms of Purcell factor, and additionally offer freedom to reach any Q at a similar Purcell factor. We discuss how these metrics are highly advantageous for a high Purcell factor, yet weak-coupling applications, such as bright sources of indistinguishable single photons. The challenges for room-temperature strong coupling, however, are far more daunting: the extremely high dephasing of emitters implies that little benefit can be achieved from trading confinement against a higher Q, as done in hybrids. An attractive alternative could be strong coupling at liquid nitrogen temperature, where emitter dephasing is lower and this trade-off can alleviate the stringent fabrication demands required for antenna strong coupling. For few-emitter strong-coupling, high-speed and low-power coherent or incoherent light sources, particle sensing and vibrational spectroscopy, hybrids provide the unique benefit of very high local optical density of states, tight plasmonic confinement, yet microcavity Q.

Strong Light–Matter Interactions Enabled by Polaritons in Atomically Thin Materials

“…In the former regime, the rate of energy exchange between the emitter and the cavity is slower than any losses pertaining to the system's constituents, and thus the light and matter states essentially remain as separate entities (albeit with modified dynamics). In the weak coupling regime, the enhancement of the electromagnetic local density of states (LDOS) and of the field enhancement provided by the optical cavity can be used to increase the emission rate of an emitter: this behavior is known as the Purcell effect . On the opposite end, that is, in the strong‐coupling regime—where the rate of energy exchange between the emitter and the cavity is faster than any losses—the light and matter states hybridize to form new eigenstates simultaneously endowed with both light‐like and matter‐like character .…”

“…In the weak coupling regime, the enhancement of the electromagnetic local density of states (LDOS) and of the field enhancement provided by the optical cavity can be used to increase the emission rate of an emitter: this behavior is known as the Purcell effect. [178][179][180][181] On the opposite end, that is, in the strong-coupling regime-where the rate of energy exchange between the emitter and the cavity is faster than any losses-the light and matter states hybridize to form new eigenstates simultaneously endowed with both light-like and matter-like character. [182] The hybrid nature of polaritons emerging in the strong-coupling regime offers many exciting opportunities not only for fundamental research [183] but also for quantum technologies such as photon blockades, [184] coherent quantum bit manipulation, [185] or new quantum light generation and thresholdless polaritonic lasers.…”

Quantized quasinormal-mode description of nonlinear cavity-QED effects from coupled resonators with a Fano-like resonance

“…II to a two-QNM multiphoton system, using first-principle calculations for a specific open-cavity structure. A typical system to study in terms of two dominant but different QNMs are metal-dielectric hybrid structures, where one mode is photon dominated and one is plasmon dominated [22,48,71], but with a sufficiently different quality factor.…”

“…For using such cavity modes to study strong coupling effects, it is clearly not appropriate to just use some quality factor and mode volume from an effective single mode JC model for the high-Q resonance, as the assumed coupling g would be overestimated by around a factor of 6. Although the effective Q is also overestimated, the absolute value of g is essential to know for including additional decay processes, such as pure dephasing, which increases as a function of temperature [71].…”

Chip‐Compatible Quantum Plasmonic Launcher

“…[5,11] Leveraging on these ultrafast emission rates, plasmonic nanostructures could enable the on-demand production of indistinguishable photons, [12] possibly even at noncryogenic temperatures. [13][14][15] In this approach, one limitation is that plasmonic materials typically exhibit relatively high ohmic losses. However, using appropriately designed cavity-antenna systems, the quenching rates due to such losses can be kept below the plasmon emission rates.…”