Superconducting single-photon detectors integrated with diamond nanophotonic circuits
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-10-09 |
| Journal | Light Science & Applications |
| Authors | Patrik Rath, Oliver Kahl, Simone Ferrari, Fabian Sproll, Georgia LewesâMalandrakis |
| Institutions | Karlsruhe Institute of Technology, Fraunhofer Institute for Applied Solid State Physics |
| Citations | 74 |
| Analysis | Full AI Review Included |
6CCVD Technical Documentation: Integrated Superconducting Single-Photon Detectors on Diamond Nanophotonics
Section titled â6CCVD Technical Documentation: Integrated Superconducting Single-Photon Detectors on Diamond NanophotonicsâThis technical documentation analyzes the integration of high-performance Superconducting Nanowire Single-Photon Detectors (SNSPDs) with diamond nanophotonic circuits, emphasizing the capabilities of 6CCVD in supplying the foundational diamond materials necessary to replicate and advance this quantum technology.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates the monolithic integration of highly efficient SNSPDs directly onto polycrystalline diamond (PCD) waveguides, establishing diamond as a robust and scalable platform for quantum integrated circuits.
- Monolithic Integration: Achieved functional SNSPDs (using NbN) integrated onto high-quality PCD thin film nanophotonic circuits.
- High Efficiency: Demonstrated exceptional On-Chip Detection Efficiency (OCDE) up to 66% at the telecom wavelength of 1550 nm.
- Ultra-Low Noise: Confirmed ultra-low noise performance with a minimum Noise Equivalent Power (NEP) of 7.9 x 10-19 W Hz-1/2.
- Fast Timing: Achieved a competitive timing jitter (FWHM) of 186 ps and a fast detector decay time of 5.1 ns, enabling maximum count rates up to 200 MHz.
- Scalable Architecture: Utilization of a traveling wave geometry overcomes traditional SNSPD absorption limitations by arbitrarily increasing the nanowire length, making the design scalable.
- Material Foundation: Success relies critically on high-quality, ultra-smooth Diamond-on-Insulator (DOI) templates fabricated via MPCVD and Chemo-Mechanical Polishing (CMP).
- Quantum Potential: This work paves the way for fully integrated diamond quantum photonics, combining detectors, waveguides, and color-center single-photon sources (e.g., NV or SiV centers) on a single chip.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Wavelength of Operation | 1550 | nm | Telecom C-band |
| On-Chip Detection Efficiency (OCDE) | 66 | % | Max measured, 65 ”m double meander |
| Minimum Noise Equivalent Power (NEPoc) | 7.9 x 10-19 | W Hz-1/2 | Measured at optimized bias (81% Icritical) |
| Dark Count Rate (DCR) | < 3 | Hz | Measured at 81% Icritical |
| Timing Jitter (FWHM) | 186 | ps | Instrument-limited resolution |
| Detector Decay Time | 5.1 | ns | Corresponds to 200 MHz max count rate |
| Operating Temperature | 1.8 | K | Liquid Helium cryostat base temperature |
| NbN Critical Temperature (Tc) | 6.5 | K | Superconducting film temperature |
| Diamond Film Thickness | 600 | nm | Post-CMP thickness on DOI template |
| Diamond Surface Roughness (Ra) | < 3 | nm | Achieved via Chemo-Mechanical Polishing |
| Waveguide Width | 1 | ”m | Half-etched rib waveguide |
| NbN Nanowire Thickness | 4.6 | nm | Sputtered superconducting layer |
Key Methodologies
Section titled âKey MethodologiesâThe core methodology involves the precise fabrication of high-quality diamond thin films and subsequent integration of superconducting materials using high-resolution lithography and etching processes.
- Diamond Template Synthesis:
- 1 ”m thick Polycrystalline Diamond (PCD) thin film deposited via Plasma-Enhanced Chemical Vapor Deposition (PECVD) onto an oxidized silicon wafer (2 ”m SiO2) to create a Diamond-on-Insulator (DOI) template.
- Surface Engineering:
- Chemo-Mechanical Polishing (CMP) reduces the diamond thickness to 600 nm and achieves an ultra-low Root Mean Square (RMS) surface roughness of Ra < 3 nm.
- Superconductor Deposition:
- 4.6 nm thick Niobium Nitride (NbN) thin film sputter-deposited onto the polished diamond surface using DC reactive magnetron sputtering (Argon/Nitrogen mixture).
- Metal Contact Fabrication:
- First Electron Beam Lithography (EBL) step defines metal contact pads (Cr/Au/Cr stack: 5 nm / 150 nm / 10 nm) using PVD and lift-off.
- Nanowire Patterning:
- Second EBL step uses 120 nm thick Hydrogen Silsesquioxane (HSQ) resist to define the NbN nanowires (< 100 nm width) in meander/double meander geometries.
- The NbN layer is subsequently etched using Argon plasma and CF4 chemistry.
- Waveguide Definition:
- Third EBL step defines the nanophotonic circuits (waveguides, couplers, splitters).
- Pattern transfer into the diamond is performed via Reactive Ion Etching (RIE) using Argon and Oxygen plasma, resulting in 1 ”m wide half-etched rib waveguides (300 nm etch depth).
- Cryogenic Testing:
- Devices are cooled to a base temperature of 1.8 K and tested using pulsed 1550 nm fiber laser sources to characterize OCDE, DCR, and timing jitter.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is an expert material science and engineering partner uniquely positioned to supply the high-purity, ultra-smooth diamond templates required to replicate and extend this foundational quantum research. The successful fabrication of these high-performance SNSPDs is fundamentally dependent on the quality and preparation of the initial MPCVD diamond film.
Custom Diamond Templates for Quantum Integration
Section titled âCustom Diamond Templates for Quantum Integrationâ| Paper Requirement/Goal | 6CCVD Solution & Capability | Engineering Impact & Value Proposition |
|---|---|---|
| Material Quality: Polycrystalline/Single Crystal Diamond Template | Optical Grade PCD & SCD. We supply MPCVD diamond films, including wafer-scale PCD up to 125 mm, and high-purity Single Crystal Diamond (SCD) for critical applications. | Provides the foundational, broadband transparent material necessary for tight light confinement and integration with next-generation single-photon color centers (NV/SiV). |
| Thickness & Confinement: 600 nm film thickness for waveguide modes | Custom Thickness Milling. We guarantee precise SCD and PCD thin film thickness control, ranging from 0.1 ”m up to 500 ”m, allowing researchers to perfectly match the required effective refractive index profiles. | Enables fine-tuning of photonic modes (TE/TM) and critical coupling parameters vital for high-efficiency traveling wave detector geometries. |
| Low Loss Waveguides: Ra < 3 nm surface smoothness | State-of-the-Art Polishing. Our standard polishing processes achieve Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD), exceeding the quality requirements cited in this paper. | Minimizes waveguide propagation loss, directly increasing the absorption length and maximizing the OCDE of the integrated SNSPD devices. |
| Electrical Integration: Cr/Au/Cr metal contact structures | In-House Custom Metalization. We offer deposition services for standard and custom stacks, including Au, Pt, Pd, Ti, W, and Cu. | Facilitates seamless integration of superconducting films (like NbN) and robust, high-frequency electrical contacts required for cryogenic readout and fast timing analysis. |
| Scalability: Wafer-scale (15 mm x 15 mm die, up to 192 detectors) | Large Area Supply & Custom Dimensions. We supply wafers up to 125 mm (PCD) with precision laser micromachining capabilities. Global Shipping (DDU/DDP) ensured. | Supports the scalable manufacturing approach demonstrated here, enabling the production of hundreds of quantum devices per run. |
Engineering Support
Section titled âEngineering SupportâThe realization of high-efficiency traveling wave detectors on diamond requires meticulous coordination between material science (polishing, deposition) and nanophotonic engineering (waveguide design). 6CCVDâs in-house PhD engineering team specializes in guiding researchers through material selection and customization for complex integrated quantum photonics applications, including optimization for 1550 nm telecom wavelengths or shorter visible wavelengths (where the paper predicts even higher efficiency).
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Photonic quantum technologies hold promise to repeat the success of integrated nanophotonic circuits in non-classical applications. Using linear optical elements, quantum optical computations can be performed with integrated optical circuits and can therefore overcome the existing limitations in terms of scalability. In addition to passive optical devices for realizing photonic quantum gates, active elements, such as single-photon sources and single-photon detectors, are essential ingredients for future optical quantum circuits. Material systems that allow for the monolithic integration of all components are particularly attractive, including III-V semiconductors, silicon and diamond. Here, we demonstrate nanophotonic integrated circuits made from high-quality polycrystalline diamond thin films in combination with on-chip single-photon detectors. By using superconducting nanowires that are coupled evanescently to traveling waves, we achieve high detection efficiencies of up to 66% as well as low dark count rates and a timing resolution of 190 ps. Our devices are fully scalable and hold promise for functional diamond photonic quantum devices.