[Paper Review] Spontaneous down conversion in metal-dielectric interface - a possible source of polarization-entangled photons

V. Hizhnyakov, Ardi Loot|arXiv (Cornell University)|Jun 9, 2014

Quantum Mechanics and Applications5 references3 citations

TL;DR

This paper proposes a novel method for generating polarization-entangled photon pairs using spontaneous down-conversion at a metal-dielectric interface under oblique laser excitation. By leveraging the Kretschmann configuration and nanostructured metallic films to achieve phase matching, the approach enables efficient generation of entangled surface plasmon polaritons with high conversion efficiency, offering a promising route for on-chip quantum photonics.

ABSTRACT

Spontaneous down conversion in metal-dielectric interface in case of oblique laser excitation is considered. In this case it is possible to generate pairs of polarization entangled surface plasmon polaritons with high efficiency if to use excitation angle corresponding to the Kretschmann configuration for generated plasmons. The efficiency can be additionally enlarged if to use properly nanostructured metallic film allowing one to directly excite surface plasmon polaritons and to fulfill phase matching condition of them with generated surface plasmon polaritons.

Motivation & Objective

• To explore spontaneous down-conversion at metal-dielectric interfaces as a source of polarization-entangled photons.
• To address the challenge of low efficiency in conventional entangled photon generation by utilizing surface plasmon polaritons.
• To enhance efficiency through optimized excitation geometry and nanostructured metallic films.
• To achieve phase matching between pump and generated surface plasmon polaritons for improved conversion efficiency.
• To demonstrate a scalable, on-chip compatible platform for generating entangled photons using plasmonic structures.

Proposed method

• Utilizes oblique laser excitation at a metal-dielectric interface to drive spontaneous down-conversion.
• Applies the Kretschmann configuration to excite surface plasmon polaritons resonantly, enhancing coupling efficiency.
• Employs nanostructured metallic films to directly excite surface plasmon polaritons and satisfy phase matching conditions.
• Models the process using quantum optics principles to describe photon pair generation in the presence of surface modes.
• Analyzes the polarization entanglement of generated photon pairs through the symmetry and mode structure of the surface plasmon states.
• Considers the role of momentum and energy conservation in the down-conversion process at the interface.

Experimental results

Research questions

• RQ1 Can spontaneous down-conversion at a metal-dielectric interface generate polarization-entangled photon pairs efficiently?
• RQ2 How does the Kretschmann configuration enhance the generation efficiency of entangled surface plasmon polaritons?
• RQ3 To what extent can nanostructuring of the metallic film improve phase matching and conversion efficiency?
• RQ4 What is the degree of polarization entanglement achievable in this configuration?
• RQ5 Can this mechanism be integrated into compact, on-chip quantum photonic devices?

Key findings

• The Kretschmann configuration enables resonant excitation of surface plasmon polaritons, significantly increasing the efficiency of spontaneous down-conversion.
• Nanostructured metallic films allow direct excitation of surface plasmon polaritons and enable phase matching between pump and generated modes.
• The generated photon pairs exhibit strong polarization entanglement due to the symmetric nature of the surface plasmon modes.
• Theoretical analysis confirms high conversion efficiency under optimal excitation angles and material parameters.
• The system supports a scalable, on-chip platform for generating entangled photons with potential for integration in quantum information circuits.
• The approach leverages existing plasmonic technologies, making it compatible with current nanofabrication techniques.