Structured polymer waveguides on distributed Bragg reflector coupling to solid state emitter
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-05-04 |
| Journal | Journal of Optics |
| Authors | Sebastian Knauer, MartĂn LĂłpezâGarcĂa, John Rarity |
| Institutions | University of Bristol |
| Citations | 7 |
| Analysis | Full AI Review Included |
Technical Documentation and Analysis: Structured Waveguides for Quantum Emitters
Section titled âTechnical Documentation and Analysis: Structured Waveguides for Quantum EmittersâAnalyzed Research Paper: Structured polymer waveguides on distributed Bragg reflector coupling to solid state emitter (Knauer et al., 2017)
Executive Summary
Section titled âExecutive SummaryâThis paper investigates the simulated optimization of light coupling from solid-state quantum emitters (Nitrogen-Vacancy (NV) centers in nanodiamonds) into structured polymer waveguides supported by a Distributed Bragg Reflector (DBR). The results demonstrate a pathway toward deterministic photon routing for quantum information systems.
- Core Achievement: Numerical simulation achieving near-deterministic light coupling from an NV dipole emitter into a structured polymer waveguide.
- Performance Metric: Peak spontaneous emission enhancement (Purcell Factor, FP) reached 6.2 for the quasi-TE waveguide mode (Mode 02) optimized at the NV Zero-Phonon Line (ZPL) wavelength of 637 nm.
- Component Design: The platform utilizes a low-index polymer waveguide structured with circular reflector holes, situated on a high-reflectivity DBR (9 pairs of SiO2/Ta2O5).
- Scalability: The design is highly scalable and applicable to other emitters and spectral ranges (e.g., NV phonon sidebands) by scaling the physical dimensions.
- 6CCVD Advantage: While the paper relies on fragile polymer systems and non-deterministic emitter placement, 6CCVD provides highly stable, low-loss, Single Crystal Diamond (SCD) substrates that serve as the intrinsic host lattice for robust, high-coherence NV centers, ensuring superior platform stability and thermal management compared to polymer-based approaches.
Technical Specifications
Section titled âTechnical SpecificationsâHard data extracted from the simulation and design parameters:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Wavelength ($\lambda$) | 637 | nm | NV Center Zero-Phonon Line (ZPL) |
| Peak Purcell Factor (FP) | 6.2 | N/A | Optimized quasi-TE dipole coupling (Mode 02) |
| Cavity Quality Factor (Q) | 220 | N/A | Calculated for optimized tapered cavity (Mode 02) |
| Mode Volume (V) | 0.195 | ”m3 | Calculated for optimized tapered cavity (Mode 02) |
| Waveguide Width (w) | 0.56 | ”m | Optimized structure dimension |
| Waveguide Height (h) | 1 | ”m | Optimized structure dimension |
| DBR Layer Pairs | 9 | N/A | SiO2 / Ta2O5 stack on silica substrate |
| DBR Reflectivity (R) | > 99.9 | % | Achieved across 660 nm to 750 nm |
| DBR Layer Refractive Indices | 1.454 / 2.03 | N/A | SiO2 / Ta2O5 (Quarter-wave stack) |
| Optimal Reflector Hole Radius | 75 | nm | Optimized untapered reflector design |
| Minimum Loss (Mode 02) | 366 | dB cm-1 | Unbounded silica substrate simulation |
Key Methodologies
Section titled âKey MethodologiesâThe core of the research relies on finite-difference time-domain (FDTD) simulations combined with eigenmode solvers to model the behavior of the nanophotonic structure.
- Material and Substrate Definition: Definition of the system: A polymer waveguide ($n=1.55$) supported on a 9-pair Distributed Bragg Reflector (DBR) stack composed of alternating quarter-wave layers of Silicon Dioxide (SiO2, $n \approx 1.454$) and Tantalum Pentoxide (Ta2O5, $n \approx 2.03$) on a silica substrate.
- Waveguide Geometry Optimization: Waveguide width ($w = 0.56$ ”m) and height ($h = 1$ ”m) were optimized to match the target wavelength of 637 nm.
- Dispersion and Loss Analysis: Simulation of quasi-TM (Mode 01) and quasi-TE (Mode 02) modes, observing the latter (Mode 02) suffers from higher substrate losses (366 dB cm-1) but offers stronger confinement.
- Reflector Integration: Circular holes were introduced into the waveguide to create a Photonic Crystal (PhC) resonator cavity. The hole radius and axial spacing ($a_{x}$) were optimized based on filling fraction ($f$) to achieve high transmission suppression (<0.1%).
- Tapering Optimization: A quadratic hole taper (decreasing hole size toward the dipole/cavity center) was introduced to improve the Q-factor by minimizing scattering losses, increasing FP from 6.1 to 6.2.
- Purcell Factor Calculation: The Purcell factor (FP) was calculated by normalizing the total emitted power of the dipole within the structure against the power emitted in a homogenous polymer environment.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research validates the strong potential of nanophotonic structures to enhance solid-state emitter performance. 6CCVD specializes in providing robust, high-purity crystalline materials that directly address the inherent limitations (fragility, non-deterministic placement, thermal instability) of the polymer/silica platform used in the study.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate and significantly extend the performance of this quantum integration platform, 6CCVD recommends transitioning from nanodiamonds embedded in polymer on a silica DBR to an integrated Single Crystal Diamond (SCD) platform.
| 6CCVD Material Recommendation | Specification | Rationale for Application |
|---|---|---|
| Optical Grade Single Crystal Diamond (SCD) | Thickness: 10 ”m to 500 ”m. Surface Finish: Ra < 1 nm (Polished). | Acts as the robust, low-loss host lattice for integrated NV centers, replacing the fragile polymer. SCD offers superior thermal and mechanical stability essential for cryogenic or high-power applications. |
| Monocrystalline Diamond on DBR (Custom) | SCD film deposited on a customer-supplied substrate (e.g., high-index material for custom DBR integration). | Provides a high-quality SCD waveguiding layer suitable for direct lithographic patterning, eliminating non-deterministic nanodiamond placement. |
| Boron-Doped Diamond (BDD) | Thickness: 0.1 ”m - 10 mm. Boron Density: Custom (P-type semiconductor). | While not directly required for NV emission, BDD films are ideal for integrated electrical contacts or thermal management layers in complex quantum devices. |
Customization Potential
Section titled âCustomization Potentialâ6CCVDâs in-house capabilities allow researchers to execute the highly precise fabrication steps required to transition this simulated design into a robust, manufactured device:
- Substrate Engineering: We provide MPCVD diamond substrates up to 125 mm (PCD) or customized SCD wafers, precisely tuned for lattice matching or specific thermal profiles.
- Precision Polishing: Achieving high Q-factors (Q=220 demonstrated here) is highly dependent on low-loss material surfaces. 6CCVD guarantees Ra < 1 nm polishing for SCD surfaces, crucial for minimizing scattering losses in structured waveguides like those modeled with 75 nm hole radii.
- Custom Microstructuring (Replication): 6CCVD offers precision laser cutting and patterning services to define the exact footprint and high-aspect ratio features necessary for replicating the optimized waveguide and reflector geometries (0.56 ”m width, 1 ”m height).
- Metalization Services: Although not the focus of this photonic study, quantum devices often require electrical contacts. We offer in-house deposition of standard quantum contact metals, including Ti/Pt/Au, Pd, and W, onto polished diamond surfaces for seamless device integration.
Engineering Support
Section titled âEngineering SupportâThe coupling of single solid-state emitters, such as NV centers, into high-Q photonic cavities requires intimate knowledge of both crystal physics and nanophotonic design. 6CCVDâs in-house PhD team has extensive experience in diamond growth, defect engineering, and material integration for quantum applications. We can assist researchers in:
- Selecting the optimal diamond grade and orientation for creating specific defect centers (e.g., shallow NV implantation for strong waveguide coupling).
- Calculating the refractive index and material stack requirements for diamond-based DBRs or high-contrast metasurfaces to surpass the performance limits of low-index polymer systems.
- Designing and supplying custom-thickness SCD films specifically for integration onto existing cleanroom processing platforms (e.g., SOI or SiC).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We simulate the coupling of light emitted by a solid state emitter into a structured polymer waveguide. The polymer waveguide is supported on a dielectric mirror making an easy to fabricate platform. This waveguide could be fabricated around a pre-selected and characterized atom like emitter such as a nitrogen vacancy center. We see near deterministic coupling of dipole emitted light into the waveguide and spontaneous emission enhancements up to a factor of 6.2 for TE dipoles coupled to cavity structures.