Quantum particle interacting with a metallic particle: Spectra from quantum Langevin theory

Abstract

The effect of a nearby metallic particle on the quantum optical properties of a quantum particle in the four-level double Raman configuration is studied using the quantum Langevin approach. We obtain analytical expressions for the correlated quantum fields of Stokes and anti-Stokes photons emitted from the system and perform analysis on how the interparticle distance, the direction of observation or detection, the strengths of controllable laser fields, the presence of surface plasmon resonance, and the number density of the quantum particle affect the quantum spectra of the Stokes and anti-Stokes fields. We explore the physics behind the quantum-particle-metallic-nanoparticle interaction within the dipole approximation, that is, when the interparticle distance is much larger than the sizes of the particles. Our results show the dependence of the spectra on the interparticle distance in the form of oscillatory behavior with damping as the interparticle distance increases. At weaker laser fields the enhancement of quantum fields which manifests itself in the form of a Fano dip in the central peak of the spectra becomes significant. Also, the quantum-particle-metallic-nanoparticle coupling, which is affected by the size of the metallic nanoparticle and the number density of the quantum particle, changes the angular dependence of the spectra by breaking the angular rotational symmetry. In the presence of surface plasmon resonance the oscillatory dependence of the spectra on the interparticle distance and angles of observation becomes even stronger due to the plasmonic enhancement effect.

Quantum plasmonics of finite-size particles with coherent anti-Stokes Raman scattering

“…The dipole transition matrix elements (aligned along x) are ℘ dc,x = ℘ db,x = ℘ ac,x = ℘ ab,x = 1.6 × 10 −29 C m. Also, we have used ε ∞ = 3.7, = 2.73 × 10 13 s −1 , and ω p = ω p0 for the plasmonic resonant case and ω p = 0.9ω p0 for the nonresonant case, with ω p0 given by Eq. (15).…”

“…Besides spherical metallic nanoparticles, systems that involve coupling between a quantum dot and multiple metallic nanoparticles [8,11], metallic nanowires [12], and metallicdielectric nanoshells [13] have also been studied. Recent studies in quantum nonlinear plasmonics include nonlinear plasmonic effects of metallic nanoparticles on a three-level quantum system (QS) with electromagnetically induced transparency [14], and quantum properties of light in a fourlevel double Raman configuration in a quantum plasmonic system [15].…”