Deterministic fabrication of dielectric loaded waveguides coupled to single nitrogen vacancy centers in nanodiamonds

At a Glance

Metadata	Details
Publication Date	2017-01-04
Journal	University of Southern Denmark Research Portal (University of Southern Denmark)
Authors	Hamidreza Siampour, Shailesh Kumar, Sergey I. Bozhevolnyi
Analysis	Full AI Review Included

Technical Documentation & Analysis: Deterministic NV Center Coupling in Diamond Waveguides

This document analyzes the research on coupling single Nitrogen Vacancy (NV) centers in nanodiamonds to dielectric loaded plasmonic waveguides, highlighting how 6CCVD’s advanced MPCVD diamond materials and fabrication services can accelerate and scale this quantum technology.

Executive Summary

Core Achievement: Successful deterministic coupling of single Nitrogen Vacancy (NV) centers, acting as quantum emitters, to dielectric loaded plasmonic waveguides.
Quantum Enhancement: The coupling mechanism significantly engineered the quantum emitter environment, resulting in a 47.5% reduction in NV center lifetime (from 14.3 ns to 7.5 ns).
Methodology: Utilized a top-down fabrication approach involving Electron Beam Lithography (EBL) of Hydrogen Silsesquioxane (HSQ) resist on a silver-coated silicon substrate.
Verification: Single-photon emission capability was confirmed through second-order correlation function measurements (antibunching dip).
Application Potential: The demonstrated platform is critical for developing integrated, on-chip components necessary for quantum information processing, such as beam splitters and cavities.
6CCVD Value Proposition: Replication and scaling of this research requires high-purity, low-strain Single Crystal Diamond (SCD) substrates, which 6CCVD provides with industry-leading surface quality (Ra < 1 nm) and custom metalization capabilities.

Technical Specifications

The following hard data points were extracted from the research detailing the performance and fabrication parameters of the coupled NV center system.

Parameter	Value	Unit	Context
Initial NV Center Lifetime (τ₀)	14.3	ns	Before waveguide coupling
Coupled NV Center Lifetime (τ_c)	7.5	ns	After waveguide coupling
Lifetime Reduction	~47.5	%	Indicates enhanced spontaneous emission rate
Emitter Type	Single Nitrogen Vacancy (NV)	N/A	Confirmed by antibunching (g²(0) < 0.5)
Substrate Base	Silicon (Si)	N/A	Used for mechanical support
Plasmonic Layer	Silver (Ag) Film	N/A	Coating applied to the Si substrate
Alignment Markers	Gold (Au)	N/A	Used for deterministic EBL alignment
Waveguide Resist	Hydrogen Silsesquioxane (HSQ)	N/A	Dielectric material patterned by EBL

Key Methodologies

The deterministic coupling relied on a precise sequence of material preparation and high-resolution lithography:

Substrate Preparation: A silicon sample was coated with a silver (Ag) film to serve as the plasmonic layer.
Marker Fabrication: Gold (Au) alignment markers were fabricated onto the silver surface to enable high-precision registration.
Emitter Deposition: Nanodiamonds containing pre-characterized single NV centers were spin-coated onto the prepared substrate.
Pre-Characterization: Confocal microscopy was used to locate and measure the initial lifetime, spectrum, and autocorrelation of the single NV centers.
Waveguide Fabrication: Dielectric loaded waveguides were deterministically written onto the pre-characterized nanodiamonds using Electron Beam Lithography (EBL) with Hydrogen Silsesquioxane (HSQ) resist.
Post-Characterization: Coupling was confirmed by observing emission from gratings at the waveguide ends and measuring the reduced NV center lifetime and maintained single-photon emission characteristics.

6CCVD Solutions & Capabilities

This research demonstrates the critical need for high-quality diamond materials and precise integration capabilities. 6CCVD is uniquely positioned to supply the necessary components for scaling this quantum photonic platform.

Applicable Materials

To transition from nanodiamonds to integrated bulk diamond platforms for scalable quantum circuits, high-purity MPCVD diamond is essential.

Optical Grade Single Crystal Diamond (SCD): Required for applications demanding the highest coherence and lowest strain. Our SCD material features ultra-low background nitrogen, enabling precise, controlled creation of NV centers (e.g., via ion implantation or delta doping) with superior stability compared to nanodiamonds.
Polycrystalline Diamond (PCD) Substrates: Available for large-area applications (up to 125 mm diameter) where the diamond layer acts as a robust, high-thermal-conductivity platform for integrated electronics or passive optical components.

Customization Potential

The fabrication process requires precise material dimensions, surface preparation, and custom metal layers for plasmonic structures and lithography alignment.

Research Requirement	6CCVD Capability	Specification Range
Surface Quality (Critical for EBL)	Ultra-Smooth Polishing	Ra < 1 nm (SCD), Ra < 5 nm (Inch-size PCD)
Custom Dimensions (Scaling)	Large Area Plates/Wafers	Up to 125 mm diameter (PCD)
Thickness Optimization	Precise Thickness Control	SCD (0.1 µm - 500 µm), Substrates (up to 10 mm)
Metalization (Ag/Au in paper)	In-House Custom Metalization	Standard stacks (Ti/Pt/Au) and custom layers (Au, Pt, Pd, Ti, W, Cu) for ohmic contacts, alignment markers, and plasmonic structures.
Patterning Support	Laser Cutting & Shaping	Custom geometries and features can be pre-cut to facilitate subsequent lithography and integration steps.

Engineering Support

6CCVD’s in-house PhD team specializes in the material science of diamond for quantum applications. We offer consultation on:

Material Selection: Choosing the optimal diamond grade (SCD vs. PCD) and doping level for specific quantum emitter applications (e.g., NV centers, SiV centers).
Surface Preparation: Ensuring the diamond surface meets the stringent requirements for high-resolution lithography (EBL) and subsequent etching processes necessary for defining integrated photonic circuits.
Integration Strategy: Assisting with the design and implementation of custom metalization stacks required for electrical contacts, thermal management, or plasmonic coupling in similar Quantum Information Processing projects.

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

Tech Support

Original Source

DOI: None