Diamond Raman laser - a promising high-beam-quality and low-thermal-effect laser
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-01-01 |
| Journal | High Power Laser Science and Engineering |
| Authors | Yulan Li, Jie Ding, Zhenxu Bai, Xuezong Yang, Yuqi Li |
| Institutions | Hebei University of Technology, Macquarie University |
| Citations | 31 |
| Analysis | Full AI Review Included |
Diamond Raman Laser Material Analysis: Leveraging 6CCVD MPCVD Diamond for High-Brightness, Kilowatt-Class Systems
Section titled âDiamond Raman Laser Material Analysis: Leveraging 6CCVD MPCVD Diamond for High-Brightness, Kilowatt-Class SystemsâExecutive Summary
Section titled âExecutive SummaryâThis review confirms that Chemical Vapor Deposition (CVD) diamond is the superior solid-state material for high-power, high-beam-quality Stimulated Raman Scattering (SRS) lasers, directly aligning with 6CCVDâs core expertise in MPCVD diamond growth.
- Thermal Superiority: Diamond exhibits thermal conductivity (up to 2200 W·mâ»Âč·Kâ»Âč) two to three orders of magnitude higher than other common Raman crystals (e.g., Ba(NOâ)â, YVOâ), minimizing thermal lensing and stress fracture under high pump power.
- Performance Benchmarks: Diamond Raman Lasers (DRLs) have achieved kilowatt-level output (up to 1.2 kW in quasi-CW operation) and demonstrated near-diffraction-limited beam quality (MÂČ as low as < 1.1) by utilizing the Raman cleanup effect.
- Wavelength Versatility: Diamondâs large Raman shift (1332.3 cmâ»Âč) and wide transparency range (> 0.23 ”m) enable efficient wavelength conversion from the deep ultraviolet (UV) to the mid-infrared (Mid-IR) via cascaded Stokes shifts.
- Material Requirement: High-purity, low-loss CVD diamond (specifically Type IIa) is essential for maximizing Raman gain (10-12 cm/GW) and conversion efficiency (up to 84% slope efficiency observed).
- Future Development: Continued research focuses on optimizing thermal management models and controlling heat distribution within the diamond crystal to push DRLs toward higher average power and brightness, potentially surpassing Raman fiber lasers.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes key material properties and performance metrics extracted from the research, highlighting the advantages of CVD diamond for high-power laser applications.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Thermal Conductivity (Diamond) | 2200 | W·mâ»Âč·Kâ»Âč | At room temperature; critical for thermal management |
| Raman Gain Coefficient | 10-12 | cm/GW | Measured @ 1064 nm |
| Raman Shift | 1332.3 | cmâ»Âč | Large shift enables wide spectral conversion |
| Transmission Range | > 0.23 | ”m | Wide range from deep UV to Mid-IR |
| Thermal Expansion Coefficient | 1.1 | Ă10â»â¶ Kâ»Âč | Extremely low, minimizing thermal stress |
| Maximum Output Power (Quasi-CW) | 1.2 | kW | Achieved in 2019 DRL experiment (1.24 ”m) |
| Minimum Beam Quality Factor | < 1.1 | MÂČ | Near-diffraction-limited output (TEM00 mode) |
| Maximum Slope Efficiency | 84 | % | Observed in pulsed external cavity DRL |
| Thermal Diffusion Length (D) | â 12 | cm2·s-1 | High diffusivity value |
Key Methodologies
Section titled âKey MethodologiesâThe successful development of high-power Diamond Raman Lasers relies on precise material engineering and advanced cavity configurations:
- Material Sourcing: Utilizing high-quality, low-birefringence CVD diamond (Type IIa) grown via MPCVD to meet the stringent requirements for Raman gain media.
- External Cavity Design: Employing external-cavity pumped structures to separate the Raman gain medium (diamond) from the pump laser crystal, effectively eliminating negative thermal effects originating from the pump source.
- Raman Cleanup Effect: Pumping the DRL with medium-beam-quality light (MÂČ typically 3-7) to leverage the automatic phase-matching property of SRS, resulting in a high-quality output Stokes beam (MÂČ < 1.1).
- Cascaded Conversion: Implementing cascaded DRLs to achieve multiple Stokes shifts, enabling wavelength conversion to eye-safe (1.5 ”m band) or Mid-IR wavelengths (up to 6 ”m proposed).
- Thermal Modeling: Analyzing thermal distribution and thermal lens effects in the diamond crystal using finite-element analysis (e.g., QuickField) and ABCD matrix methods to predict cavity stability and optimize operational parameters under high-power CW and quasi-CW modes.
- Custom Crystal Fabrication: Using specific geometries, such as Brewster-cut diamond crystals, to minimize reflection losses and optimize cavity alignment.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & Capabilitiesâ6CCVD is uniquely positioned to supply the high-specification MPCVD diamond materials and custom fabrication services required to replicate and advance the research outlined in this paper. Our capabilities directly address the need for high-purity, low-loss, thermally stable Raman gain media.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the high Raman gain and superior thermal management demonstrated in DRLs, researchers require the highest quality CVD diamond.
| Research Requirement | 6CCVD Solution | Technical Justification |
|---|---|---|
| Raman Gain Medium | Optical Grade Single Crystal Diamond (SCD) | High-purity Type IIa material ensures minimal absorption loss and maximum Raman gain coefficient (10-12 cm/GW). |
| High Power Substrates | Thick SCD or High-Purity PCD Substrates | SCD available up to 500 ”m thickness; Substrates up to 10 mm available for robust thermal management in kW-class systems. |
| Boron Doping | Boron-Doped Diamond (BDD) | Available for future research requiring electro-optic modulation or integrated thermal sensing capabilities. |
Customization Potential
Section titled âCustomization PotentialâThe paper highlights the use of specific crystal dimensions (e.g., 7.8 mm Ă 7.8 mm Ă 1.05 mm) and specialized coatings. 6CCVD offers comprehensive customization to meet precise experimental needs:
- Custom Dimensions: We supply plates and wafers up to 125 mm (PCD) and offer custom laser cutting and shaping for SCD crystals, including precise dimensions and Brewster-cut geometries required for external cavities.
- Polishing Excellence: To minimize scattering losses and maintain the high beam quality (MÂČ < 1.1) achieved via the Raman cleanup effect, 6CCVD guarantees ultra-low surface roughness:
- SCD: Ra < 1 nm
- PCD (Inch-size): Ra < 5 nm
- Advanced Metalization: The DRL cavity requires highly reflective (HR) and output coupling (OC) mirrors. 6CCVD provides in-house metalization services, including deposition of Au, Pt, Pd, Ti, W, and Cu, allowing for integrated mirror coatings directly onto the diamond crystal faces.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and laser engineers specializes in the interaction between high-power lasers and diamond. We offer critical support for similar High-Brightness Raman Laser projects:
- Material Selection: Consultation on optimizing crystal orientation, thickness, and purity to maximize conversion efficiency and minimize thermal effects (thermal lensing, birefringence).
- Thermal Analysis Guidance: Assistance in selecting the optimal diamond geometry (e.g., slab or disk configurations) to manage heat deposition and maintain cavity stability under CW and quasi-CW operation, particularly when scaling power beyond the kilowatt level.
- Global Logistics: We ensure reliable global shipping (DDU default, DDP available) for time-sensitive research projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract Stimulated Raman-scattering-based lasers provide an effective way to achieve wavelength conversion. However, thermally induced beam degradation is a notorious obstacle to power scaling and it also limits the applicable range where high output beam quality is needed. Considerable research efforts have been devoted to developing Raman materials, with diamond being a promising candidate to acquire wavelength-versatile, high-power, and high-quality output beam owing to its excellent thermal properties, high Raman gain coefficient, and wide transmission range. The diamond Raman resonator is usually designed as an external-cavity pumped structure, which can easily eliminate the negative thermal effects of intracavity laser crystals. Diamond Raman converters also provide an approach to improve the beam quality owing to the Raman cleanup effect. This review outlines the research status of diamond Raman lasers, including beam quality optimization, Raman conversion, thermal effects, and prospects for future development directions.