Highly efficient heat extraction by double diamond heat-spreaders applied to a vertical external cavity surface-emitting laser
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2017-08-08 |
| Journal | Optical and Quantum Electronics |
| Authors | Artur Broda, Aleksandr KuĆșmicz, G Rychlik, Krzysztof Chmielewski, Anna WĂłjcik-JedliĆska |
| Institutions | Institute of Electron Technology, Warsaw University of Technology |
| Citations | 20 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Efficiency Diamond Heat Spreaders for VECSELs
Section titled âTechnical Documentation & Analysis: High-Efficiency Diamond Heat Spreaders for VECSELsâExecutive Summary
Section titled âExecutive SummaryâThis research demonstrates a breakthrough in thermal management for Vertical External Cavity Surface-Emitting Lasers (VECSELs) by utilizing a DBR-free structure enclosed by two transparent diamond heat-spreaders. 6CCVDâs high-purity Single Crystal Diamond (SCD) is the ideal material solution for replicating and advancing this technology.
- Thermal Performance: Achieved an estimated thermal resistance (Rth) of below 0.2 K/W in the double-diamond, DBR-free VECSEL structure.
- Efficiency Gain: This Rth value represents a 15-fold decrease in thermal resistance compared to standard DBR structures, overcoming the thermal limits imposed by high-resistivity DBRs.
- Power Stability: The double-diamond configuration successfully eliminated thermal rollover of the power conversion characteristic up to the maximum available pump power (22 W).
- Spectral Stability: Spectral drift of stimulated emission was strongly reduced, confirming superior heat dissipation from both sides of the active region.
- Material Requirement: The experiment relied on high-quality CVD diamond plates (3 x 3 mmÂČ, 300 ”m thick) with ultra-low surface roughness (RMS < 0.54 nm) and high thermal conductivity (2000 W/mK).
- Application: This methodology enables the realization of high-power semiconductor lasers operating at wavelengths previously limited by surface-emitting device thermal constraints.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the research, highlighting the critical performance metrics achieved using diamond heat spreaders.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Thermal Resistance (Rth) | < 0.2 | K/W | DBR-free, Double Diamond Configuration |
| Thermal Resistance (Rth) | 2.9 | K/W | Standard VECSEL, Single Diamond Configuration |
| Thermal Conductivity (Diamond) | 2000 | W/mK | Required material property for heat spreader |
| Diamond Heat Spreader Dimensions | 3 x 3 | mmÂČ | Area used in the experiment |
| Diamond Heat Spreader Thickness | 300 | ”m | Thickness used in the experiment |
| Diamond Surface Roughness (RMS) | 0.54 | nm | Required optical quality for bonding interface |
| Active Region Emission Wavelength | 971 | nm | Measured photoluminescence (PL) |
| Maximum Output Power Achieved | 3.5 | W | DBR-free, limited by pump power |
| Spectral Drift Coefficient (Bandgap) | 0.33 | nm/K | Characteristic of QW bandgap change |
| Spectral Drift Coefficient (Refractive Index) | 0.11 | nm/K | Characteristic of standard VECSEL drift |
| Pump Wavelength | 808 | nm | High power semiconductor laser bar |
Key Methodologies
Section titled âKey MethodologiesâThe successful implementation of the double-diamond VECSEL relied on precise material preparation, bonding, and substrate removal techniques.
- Heterostructure Growth: InGaAs/GaAs DBR-free and standard VECSEL heterostructures were grown on GaAs substrates using Molecular Beam Epitaxy (MBE).
- Active Region Design: The active region consisted of eight 8 nm thick InGaAs/GaAs Quantum Wells (QWs) separated by GaAs barriers, designed for resonant periodic gain (RPG) at 970 nm.
- Diamond Preparation: CVD-grown diamond plates (3 x 3 mmÂČ, 300 ”m thick) were selected based on high thermal conductivity and excellent surface morphology (RMS 0.54 nm).
- Initial Bonding: 2 x 2 mmÂČ semiconductor samples were joined to the first diamond plate using capillary bonding (Liau 2000) at room temperature under tension.
- Substrate Removal: The GaAs substrate was removed by lapping, followed by selective wet etching using NH3OH:H2O2:H2O solution, stopping on an AlAs etch-stop layer.
- Final Structure: The AlAs layer was removed (HF:H2O solution), resulting in a symmetric active region enclosed by identical window layers and 10 nm thin GaAs cap layers.
- Double Diamond Assembly: The resulting heterostructure was inserted into a copper mount, and the second diamond heat-spreader was attached by firmly pressing it against the surface, allowing heat extraction from both sides.
- Optical Pumping: The mounted laser was optically pumped using an 808 nm laser bar, with the mount temperature precisely controlled by a highly efficient thermoelectric cooler and water flow.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD specializes in providing the high-quality MPCVD diamond materials necessary to replicate and scale this high-power VECSEL thermal management solution. Our capabilities directly address the stringent requirements for thermal conductivity, optical quality, and precise dimensions demanded by this research.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the estimated thermal resistance of < 0.2 K/W and maintain low absorption/birefringence, the highest quality diamond is essential.
| 6CCVD Material Solution | Specification | Relevance to Research |
|---|---|---|
| Optical Grade SCD | Thermal Conductivity: > 2000 W/mK. Low Nitrogen content (< 1 ppb). | Matches the high thermal conductivity cited (2000 W/mK) and ensures minimal optical absorption and birefringence required for intracavity use. |
| High-Purity PCD | Plates up to 125 mm diameter. Thickness up to 500 ”m. | For applications requiring larger area heat spreaders or substrates where single-crystal material is cost-prohibitive. |
| Polishing Service | SCD: Ra < 1 nm. PCD: Ra < 5 nm (Inch-size). | Critical for successful capillary bonding and minimizing scattering losses at the semiconductor/diamond interface (RMS 0.54 nm requirement). |
Customization Potential
Section titled âCustomization PotentialâThe research utilized specific 3 x 3 mmÂČ x 300 ”m plates. 6CCVD offers full customization to meet exact experimental or production needs.
- Custom Dimensions and Thickness: 6CCVD can supply SCD or PCD plates in the exact 3 x 3 mmÂČ format used, or scale up to larger dimensions (PCD up to 125 mm diameter) and thicknesses (SCD/PCD from 0.1 ”m to 500 ”m) for high-power industrial systems.
- Precision Laser Cutting: We provide precise laser cutting services to achieve the required 2 x 2 mmÂČ semiconductor sample size and the irregular shapes mentioned in the paper, which suppress lateral lasing.
- Metalization and AR Coatings: Although the paper noted that the diamonds were not covered by antireflection (AR) layers, future optimization requires them. 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) and can assist in designing custom AR coatings to minimize Fabry-Perot modes and maximize out-coupling efficiency.
Engineering Support
Section titled âEngineering SupportâThe successful implementation of DBR-free VECSELs requires deep expertise in thermal modeling and material interface science.
- Thermal Management Consultation: 6CCVDâs in-house PhD team specializes in thermal modeling and material selection for high-power laser applications, including VECSELs and SDLs. We can assist researchers in optimizing diamond thickness and bonding techniques to achieve Rth values below 0.2 K/W for similar high-power semiconductor laser projects.
- Global Logistics: We ensure reliable global shipping (DDU default, DDP available) of sensitive, high-purity diamond materials directly to your lab or fabrication facility.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
We compare the heat extraction efficiency for a standard Vertical External Cavity Surface-Emitting Laser and the distributed Bragg reflector (DBR)-free structure employing a single and double diamond heat-spreaders, respectively. Both heterostructures grown by Molecular Beam Epitaxy employ two identical active regions designed for emission at 980 nm. We show that the thermal resistance has been decreased 15 times when there is no DBR and heat is extracted from both side of active region. For DBR-free laser no thermal rollover of power conversion characteristic was observed in the range of considered input powers.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
Section titled âReferencesâ- 2010 - Semiconductor Disk Lasers. Physics and Technology [Crossref]
- 2010 - Semiconductor Disk Lasers. Physics and Technology