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Register a new userTunable narrow band source via the strong coupling between optical emitter and nanowire surface plasmons
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The spectrum width can be narrowed to a certain degree by decreasing the coupling strength for the two-level emitter coupled to the propagating surface plasmon. But the width can not be narrowed any further because of the loss of the photon out of system by spontaneous emission from the emitter. Here we propose a new scheme to construct a narrow-band source via a one-dimensional waveguide coupling with a three-level emitter. It is shown that the reflective spectrum width can be narrowed avoiding the impact of the loss. This approach opens up the possibility of plasmonic ultranarrow single-photon source.
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In plasmonic chirality, the phenomenon of circular dichroism for achiral nanoparitcles caused by Coulomb interaction between metal nanoparticles (NPs) and chiral molecules have been studied. At the same time, under the resonance condition, the dye molecules and metal NPs will produce huge Rabi splitting due to strong coupling. If the chiral molecules are at the resonance of the plasmon, what will happen for the strong interaction between the plasmon and molecules with chirality introduced? In this paper, we investigate a spherical core-shell model and analyze its spectral phenomena under the excitation of circularly polarized light (CPL). Based on Coulomb interaction between NPs and chiral molecules, we will show how the various factors affect the strong coupling. We have obtained three mechanisms for the interaction between plasmons and chiral molecules: strong coupling (Rabi splitting up to 243mev), enhanced absorption and induced transparency. The interaction between CPL and chiral molecules with the opposite chirality to CPL is stronger than that of the same chirality, and the line width of the two peaks is closer than that of the same chirality, which shows that for the Rabi splitting with chirality, there are deeper mechanisms for the interaction. This result will be helpful for further research on the interaction between plasmon and molecules with chirality.
We present an efficient and robust source of photons at the $^{87}$Rb D1-line (795 nm) with a narrow bandwidth of $delta=226(1)$ MHz. The source is based on non-degenerate, cavity-enhanced spontaneous parametric down-conversion in a monolithic optical parametric oscillator far below threshold. The setup allows for efficient coupling to single mode fibers. A heralding efficiency of $eta_{mathrm{heralded}}=45(5)$ % is achieved, and the uncorrected number of detected photon pairs is $3.8 times 10^{3}/(textrm{s mW})$. For pair generation rates up to $5times 10^{5}/$s, the source emits heralded single photons with a normalized, heralded, second-order correlation function $g^{(2)}_{c}<0.01$. The source is intrinsically stable due to the monolithic configuration. Frequency drifts are on the order of $delta/20$ per hour without active feedback on the emission frequency. We achieved fine-tuning of the source frequency within a range of $ > 2$ GHz by applying mechanical strain.
The radiative decay of quantum dot (QD) excitons into surface plasmons in a cylindrical nanowire is investigated theoretically. Maxwells equations with appropriate boundary conditions are solved numerically to obtain the dispersion relations of surface plasmons. The radiative decay rate of QD excitons is found to be greatly enhanced at certain values of the exciton bandgap. Analogous to the decay of a two-level atom in the photonic crystal, we first point out that such an enhanced phenomenon allows one to examine the non-Markovian dynamics of the QD exciton. Besides, due to the one dimensional propagating feature of nanowire surface plasmons, remote entangled states can be generated via super-radiance and may be useful in future quantum information processing.
In this letter, we demonstrate that in both classical and quantum open systems, the Hamiltonian interaction between subsystems, along with relaxations caused by the interaction with reservoirs, results in the appearance of effective non-Hermitian coupling. It is determined by a gradient of density of states of reservoirs. We show that for a power-law frequency dependence of the density of states, the non-Hermitian coupling is proportional to a product of the Hermitian coupling strength and the relaxation rates. As a result, this non-Hermitian coupling begins to play a crucial role with increasing Hermitian coupling strength between the subsystems and leads to a qualitative change in the behavior of non-Hermitian systems. Namely, when the Hermitian coupling strength exceeds a critical value, the non-Hermitian coupling becomes so large that it guarantees that the system is in the strong coupling regime at any relaxation rate. This critical coupling can be associated with the transition point to the ultra-strong coupling regime, which, until now, has not been defined exactly.
In this Letter we show that the strong coupling between a disordered set of molecular emitters and surface plasmons leads to the formation of spatially coherent hybrid states extended on acroscopic distances. Young type interferometric experiments performed on a system of J-aggregated dyes spread on a silver layer evidence the coherent emission from different molecular emitters separated by several microns. The coherence is absent in systems in the weak coupling regime demonstrating the key role of the hybridization of the molecules with the plasmon.
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