213.4 W Continuous-Wave Diamond Raman Laser at 1240 nm with Polarization-Combined Pumping

At a Glance

Metadata	Details
Publication Date	2025-10-24
Journal	High Power Laser Science and Engineering
Authors	Muye Li, Yuxiang Sun, Huawei Jiang, Xuezong Yang, Yan Feng
Institutions	University of Chinese Academy of Sciences
Analysis	Full AI Review Included

Technical Documentation & Analysis: High-Power Diamond Raman Lasers

Executive Summary

This research demonstrates a significant advancement in high-power laser technology, leveraging the exceptional properties of MPCVD Single Crystal Diamond (SCD) as a gain medium.

Record Output Power: Achieved a record-breaking 213.4 W Continuous-Wave (CW) Stokes output at 1240 nm, surpassing the decade-old 154 W record for fundamental Stokes CW DRLs.
High Efficiency: The system demonstrated a high slope efficiency of 64.1% and 39.2% optical-to-Stokes conversion efficiency at 544 W combined pump power.
Thermal Robustness: Diamond’s superior thermal conductivity (up to 2000 W/(m·K)) and low thermo-optic coefficient enabled sustained operation above 200 W, confirming its potential for kilowatt-class CW applications.
Methodology: Power scaling was achieved using polarization beam combining of dual fiber lasers and a quasi-Z-shaped cavity designed to mitigate back-reflection and reduce intracavity power density.
Critical Challenges: Successful operation required stringent thermal management (TEC stabilization at 30°C) and effective suppression of parasitic Stimulated Brillouin Scattering (SBS) via cavity length tuning and spatial filtering.
Material Requirement: The success hinges on the use of high-purity, low-loss Single Crystal Diamond (SCD) with high-damage-threshold Anti-Reflective (AR) coatings, a core offering of 6CCVD.

Technical Specifications

The following hard data points were extracted from the experimental results, highlighting the performance metrics achieved using the diamond gain medium.

Parameter	Value	Unit	Context
Maximum Stokes Output Power	213.4	W	Record CW performance
Stokes Wavelength	1240	nm	Output wavelength
Maximum Combined Pump Power	544	W	Used for peak output
Slope Efficiency	64.1	%	Under combined pumping regime
Optical-to-Stokes Conversion	39.2	%	Maximum conversion efficiency
Stokes Threshold	211	W	Pump power required for oscillation
Diamond Dimensions	2 x 2 x 7	mm³	Single-crystal gain medium (Type IIa)
Diamond Operating Temperature	30	°C	Maintained by Thermoelectric Cooler (TEC)
Diamond Thermal Conductivity	2000	W/(m·K)	Key material property
Raman Frequency Shift	1332.3	cm⁻¹	Characteristic shift
Stokes Beam Waist Radius	50	µm	Calculated radius inside the diamond
Pump Beam Waist Radius	26	µm	Calculated radius inside the diamond
Output Coupler Transmissivity (T)	3.2	%	T @ 1240 nm (M4)
SBS Suppression Threshold	75	W	Stokes power level before significant SBS emergence

Key Methodologies

The successful power scaling was dependent on precise engineering and control over the diamond material and cavity dynamics:

Pump Source Combination: Polarization beam combining was used to merge two fiber lasers (Primary: up to 350 W, Secondary: up to 200 W) with orthogonal polarization, achieving high total pump power (544 W) while maintaining polarization-independent gain enhancement.
Cavity Architecture: A single-pass quasi-Z-shaped resonator was implemented to optimize intracavity power density, suppress back-reflection (via tilted optics), and enhance output efficiency.
Gain Medium Selection: A 2x2x7 mm³ Type IIa Single Crystal Diamond (SCD) was used, cut for propagation along the [110] direction, and coated with Anti-Reflective (AR) layers at 1064 nm (pump) and 1240 nm (Stokes).
Thermal Stabilization: Active thermal management was critical, utilizing water-cooled mirror mounts and a Thermoelectric Cooler (TEC) module to maintain the diamond temperature precisely at 30°C, mitigating thermal lens effects.
Parasitic Suppression: Stimulated Brillouin Scattering (SBS), a dominant loss mechanism, was suppressed by tuning the cavity length to excite high-order transverse modes in the SBS field, coupled with an intracavity aperture for spatial filtering.
Mode Control: A plano-convex lens (200 mm focal length) was used for mode-matching, ensuring the Stokes beam consistently exhibited a fundamental TEM₀₀ mode profile.

6CCVD Solutions & Capabilities

The achievement of a 213.4 W CW DRL underscores the necessity of ultra-high-quality, custom-engineered diamond materials. 6CCVD is uniquely positioned to supply the materials and customization required to replicate, scale, and advance this high-power Raman laser technology.

Applicable Materials

To replicate or extend this high-power DRL research, the highest purity diamond is required to minimize absorption and maximize thermal performance.

Optical Grade Single Crystal Diamond (SCD): We provide high-purity, low-birefringence SCD plates (analogous to Type IIa) essential for high-power Raman gain media. Our SCD material ensures the exceptional thermal conductivity (2000 W/(m·K)) and low thermo-optic coefficient necessary for stable CW operation above 200 W.
Custom Thickness and Substrates: While the paper used a 7 mm length, 6CCVD offers SCD thicknesses from 0.1 µm up to 500 µm, and custom substrates up to 10 mm thick, allowing for optimization of gain length and thermal sinking capacity.

Customization Potential

The success of the DRL depends heavily on the precise geometry and coating performance of the diamond crystal.

Requirement from Paper	6CCVD Customization Capability	Value Proposition
Custom Dimensions (2x2x7 mm³)	We offer custom laser cutting and shaping for plates/wafers up to 125 mm in size, ensuring precise replication of the required 2x2x7 mm³ geometry or scaling to larger volumes.	Enables rapid prototyping and scaling of DRL cavity designs.
Anti-Reflective (AR) Coatings	6CCVD provides custom, high-damage-threshold dielectric coatings. We can tailor AR coatings specifically for the 1064 nm pump and 1240 nm Stokes wavelengths.	Minimizes residual reflectivity (< 0.5%) and prevents the coating detachment failure observed in the experiment.
Surface Finish	Our SCD polishing achieves an ultra-low surface roughness (Ra < 1 nm).	Reduces scattering losses and significantly increases the optical damage threshold required for kilowatt-level intracavity power densities.
Metalization (Future Scaling)	Internal capability for metalization (Au, Pt, Ti, W, Cu).	Useful for integrating diamond into advanced thermal management systems or for creating micro-structured components.

Engineering Support

The challenges faced in this research—specifically managing polarization-dependent gain and suppressing SBS—are complex material science problems.

Raman Application Expertise: 6CCVD’s in-house PhD engineering team specializes in optimizing diamond material properties (crystallographic orientation, purity, and surface finish) for high-power Raman applications.
Thermal and Optical Modeling: We provide consultation on material selection and geometry optimization to manage thermal effects and mitigate birefringence, which caused the 4° polarization deviation observed in the experiment.
Global Supply Chain: We offer reliable global shipping (DDU default, DDP available) to ensure researchers worldwide receive their custom diamond components quickly and securely.

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

Tech Support

Original Source

DOI: https://doi.org/10.1017/hpl.2025.10077