Spatio-temporal second-order quantum correlations of surface plasmon polaritons

At a Glance

Metadata	Details
Publication Date	2015-12-16
Journal	Optics Letters
Authors	Martin Berthel, S. Huant, Aurélien Drezet
Institutions	Institut Néel
Citations	9
Analysis	Full AI Review Included

Technical Documentation & Analysis: Quantum Plasmonics using MPCVD Diamond

This document analyzes the research paper “Spatio-temporal second-order quantum correlations of surface plasmon polaritons” and outlines how 6CCVD’s specialized MPCVD diamond materials and fabrication services can accelerate and scale this critical research in quantum plasmonics and integrated nanophotonics.

Executive Summary

Core Achievement: Demonstration of spatio-temporal second-order quantum coherence (g⁽²⁾) of Surface Plasmon Polaritons (SPPs) launched by Nitrogen Vacancy (NV) centers.
Material Focus: Utilizes NV centers confined in nanodiamonds (NDs) coupled to a 50 nm thin silver (Ag) film on a glass substrate.
Methodology: Combines Near-Field Scanning Optical Microscopy (NSOM), Leakage Radiation Microscopy (LRM), and Hanbury Brown and Twiss (HBT) interferometry to measure quantum correlations in the Fourier space.
Quantum Signature: Confirms the quantum nature of the SPPs via clear antibunching dips (g⁽²⁾(0) < 1), validating the approach for genuine wave-particle duality tests.
Performance Enhancement: Coupling the NV centers to the Ag film significantly enhances the quantum yield (Q) from 27% (on glass) to 74% (on Ag), while reducing the spontaneous emission lifetime (T₂₁) by a factor of six (from 60 ns to 9.7 ns).
6CCVD Value Proposition: High-purity Single Crystal Diamond (SCD) substrates are essential for transitioning from the current ensemble study (N=10 NV centers) to deterministic single-emitter quantum plasmonics (N=1), offering superior thermal management and ultra-low strain.

Technical Specifications

The following hard data points were extracted from the experimental results, focusing on material and performance metrics:

Parameter	Value	Unit	Context
Substrate Material	Glass	-	170 µm thick
Metal Film Material	Silver (Ag)	-	50 nm thick
Excitation Wavelength	532	nm	CW Diode Laser
Emission Wavelength Range	650 - 750	nm	SPP characterization
SPP Effective Index (n_SPP)	1.04	-	Measured in Fourier plane
NV Center Count (N)	10	-	Ensemble average in nanodiamonds
Tip-Surface Distance	10 - 20	nm	During ND grafting/coupling
Spontaneous Emission Lifetime (T₂₁)	60	ns	Facing glass (reference)
Spontaneous Emission Lifetime (T₂₁)	9.7	ns	Facing silver (6x reduction)
Quantum Yield (Q)	27	%	Facing glass
Quantum Yield (Q)	74	%	Facing silver (2.7x increase)
Collection Fiber Area Diameter	4	µm	Reduced by microscope magnification

Key Methodologies

The experiment utilized a complex near-field optical setup coupled with quantum correlation measurements:

Sample Fabrication: A 170 µm glass substrate was prepared, half-covered with a 50 nm Ag film. Nanodiamonds (NDs) hosting approximately N=10 NV centers were deposited on the non-metalized section.
NSOM Tip Preparation: A chemically etched single-mode optical fiber tip was glued onto a quartz tuning fork and coated with a positively-charged polymer to facilitate ND grafting.
ND Grafting: The NSOM tip was scanned over a preselected ND, and the tip-surface distance was reduced to 10-20 nm to force contact and graft the ND onto the tip apex.
Excitation and Filtering: The NV centers were excited using a CW 532 nm diode laser injected into the fiber. The collected fluorescence was filtered using a dichroic mirror and a long-pass dielectric filter (λ_cut-on = 580 nm).
LRM/HBT Integration: The filtered signal was directed into a spatial HBT correlator, which included a beam splitter and two motorized collection fibers (MCF1, MCF2) coupled to Avalanche Photodiodes (APDs).
Correlation Measurement: The motorized fibers were used to precisely locate and scan two different points (A and B) in the LRM Fourier plane, enabling the measurement of auto-correlation (g⁽²⁾(τ, k_A, k_A)) and cross-correlation (g⁽²⁾(τ, k_A, k_B)) functions.
Data Analysis: The g⁽²⁾ curves were fitted using a three-level system model to determine photophysical parameters, confirming the strong enhancement of NV emission when coupled to the plasmonic Ag film.

6CCVD Solutions & Capabilities

This research demonstrates the critical role of high-quality materials and precise surface engineering in advancing quantum plasmonics. 6CCVD provides the necessary MPCVD diamond platforms to replicate, scale, and extend these findings, particularly in the transition from ensemble (N=10) to single-emitter (N=1) quantum systems.

Research Requirement	6CCVD Solution & Value Proposition
High-Purity NV Host Material	Electronic Grade Single Crystal Diamond (SCD): The paper used nanodiamonds hosting N=10 NV centers. To achieve true single-photon source performance (N=1), ultra-low strain and high-purity SCD plates (0.1 µm to 500 µm thickness) are required for deterministic NV creation via implantation or growth.
Substrate Integration & Scaling	Custom Dimensions and Thickness: 6CCVD offers SCD substrates up to 10 mm thick and Polycrystalline Diamond (PCD) plates up to 125 mm in diameter. This capability supports the scaling of LRM/NSOM experiments into integrated quantum circuits, moving beyond small glass substrates.
Surface Quality for Near-Field Coupling	Precision Polishing (Ra < 1 nm for SCD): The experiment relies on maintaining a critical 10-20 nm tip-surface distance. 6CCVD guarantees ultra-low surface roughness (Ra < 1 nm on SCD) essential for minimizing scattering losses and ensuring reproducible near-field coupling efficiency.
Integrated Plasmonic Structures	Custom Metalization Services: The paper used a 50 nm Ag film. 6CCVD provides in-house deposition of thin films (Au, Pt, Pd, Ti, W, Cu) directly onto diamond substrates. This allows researchers to integrate robust plasmonic antennas (e.g., Ti/Pt/Au stacks) directly onto the high-thermal-conductivity diamond platform.
Active Device Integration	Boron-Doped Diamond (BDD): For future experiments requiring electrical control of the plasmonic environment or NV charge state, 6CCVD offers highly conductive BDD films, enabling the integration of electrical gates or micro-heaters alongside the optical structures.
Engineering Support	6CCVD’s in-house PhD team specializes in material selection and optimization for quantum sensing and nanophotonics applications. We provide consultation on optimizing diamond growth parameters (e.g., nitrogen concentration, orientation) to maximize NV center yield and coherence time for similar quantum plasmonics projects.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

We present an experimental methodology to observe spatio-temporal second-order quantum coherence of surface plasmon polaritons which are emitted by nitrogen vacancy color centers attached at the apex of an optical tip. The approach relies on leakage radiation microscopy in the Fourier space, and we use this approach to test wave-particle duality for surface plasmon polaritons.

Tech Support

Original Source

DOI: https://doi.org/10.1364/ol.41.000037