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Physica status solidi. C, Conferences and critical reviews/Physica status solidi. C, Current topics in solid state physics

Cover Picture: Phys. Status Solidi C 2–3/2016

Published Mar 1, 2016• 0 citations
Publisher

Abstract

Coherent light sources pumped by external fields require multi-level systems to achieve a population inversion and they always convert an input frequency into lower one. In their paper on pp. 105–108, Hata and coworkers, however, theoretically proposed a frequency up-conversion luminescence from a two-level system with inverted population. The two-level system interacts with a metallic nano-antenna sustaining a localized surface plasmon-polariton. The obtained result shows that a strong and off-resonant Gaussian pulse laser with optimum peak intensity realizes the population inversion of the two-level system, which generates the up-converted luminescence. This demonstration indicates the potential applications of the present system in novel coherent light sources.

DOI
10.1002/pssc.201670114

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Coherent light sources pumped by external fields require multi-level systems to achieve a population inversion and they always convert an input frequency into lower one. In their paper on pp. 105–108, Hata and coworkers, however, theoretically proposed a frequency up-conversion luminescence from a two-level system with inverted population. The two-level system interacts with a metallic nano-antenna sustaining a localized surface plasmon-polariton. The obtained result shows that a strong and off-resonant Gaussian pulse laser with optimum peak intensity realizes the population inversion of the two-level system, which generates the up-converted luminescence. This demonstration indicates the potential applications of the present system in novel coherent light sources.
Abstract A novel technique for up‐converted luminescence generation from a two‐level molecule via population inversion is studied using the quantum toy model; this model is used to represent a coupled‐molecule and metallic nano‐antenna system sustaining a localized surface plasmon polariton (LSPP). The metallic nano‐antenna is assumed to have anharmonicity, reflecting experimentally observed results. The system is driven by a strong, offresonant, and Gaussian pulse laser so that the LSPP exhibits a Mollow triplet spectrum. When the two‐level molecular resonance is tuned to the upper Mollow triplet sideband, the molecular‐level population is inverted. We discuss the population dynamics, the Purcell effect, and the up‐converted luminescence activity of the two‐level molecule. These results indicate the potential applications of the present system in novel coherent light sources. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
We theoretically study a novel up-converted luminescence from a two-level molecule coupled with an auxiliary system such as an anharmonic LC resonator and a metallic nano-antenna. The auxiliary system is assumed to be strongly driven by a continuous wave laser so that a Mollow triplet appears in the luminescent spectrum. When the peak energy of the upper Mollow triplet sideband is tuned to the molecular excited level, the intensity of the up-converted luminescence is considerably enhanced. At the same time, the population of the two-level molecule is inverted. We also discuss the conditions for high photoemission efficiency in the up-converted luminescence under a highly inverted population. This result indicates the potential applications in future single-molecule lasers.
We theoretically propose a new method for generating up-converted coherent light from two-level systems (TLSs) coupled with a plasmonic nanocavity. The emission spectrum of a TLS excited by a strong laser exhibits a triplet structure called the Mollow triplet. If the lower Mollow sideband is tuned to the cavity mode energy, population inversion of a TLS occurs. When the driving laser is abruptly truncated under this condition, an up-converted photon is emitted from the TLSs. We also predict the up-converted superfluorescence from an ensemble of TLSs as a correlation effect among the excited states of the TLSs.
Abstract On the basis of our theoretical model of the population transfer between two levels interacting suddenly with an intense laser pulse (Zhang et al 2017 J. Phys. B: At. Mol. Opt. Phys. 50 185603), we investigate the mechanism of the population inversion between the electronically excited B 2 Σ u + state and the electronic ground X 2 Σ g + state of N 2 + achieved by the irradiation of a near-IR (800 nm) intense laser pulse, leading to the generation of the coherent emission at 391 nm. We show that one of the Floquet states generated at the moment when N 2 + starts interacting with an intense laser pulse is adiabatically connected to the ground vibrational state of the electronic B 2 Σ u + state and keeps a constant population throughout the period of the interaction with the light field, indicating that the efficient off-resonance B 2 Σ u + – X 2 Σ g + transition proceeds.
Abstract Quantum coherence and interference offer novel pathways to control light–matter interaction at the atomic scale, with enticing prospects in both fundamental and applied science. Here, we demonstrate coherent control over transient excitation of localized surface plasmon modes of a silver nanosphere adjacent to a quantum coherence medium composed of three-level quantum emitters, using a theoretical approach. We show that quantum interference enables more than two orders of magnitude enhancement in the surface plasmon field generated when the quantum emitters are driven coherently, in comparison to incoherent pumping. Furthermore, under optimal conditions, intense surface plasmon lasing can be induced without population inversion on the spasing transition. Our results open up the possibility of overcoming dissipative losses in plasmonic modes in the transient regime when steady-state population inversion is difficult to achieve due to fast relaxation rates and impractical pumping requirements.
Theoretically predicted ''dipole lasing'', i.e., spontaneous excitation of coherent metal nano-particle dipole oscillations through interaction with a quantum-dot two-level system subject to population inversion is demonstrated. Equations for dipole lasing are the same as equations for ordinary laser, where the dipole momentum of nano-particle stands for the electromagnetic field cavity mode. Dipole lasing frequency corresponds to the localized plasmon resonance of the nano-particle. Dipole momentum of nano-particle leads to coherent dipole radiation. Optical cavity is not necessary, the size of the dipole laser can be smaller than the optical wavelength, i.e. it is dipole nano-laser. Threshold conditions and optical bistability in dipole nano-lasers are considered.