High-power free-running single-longitudinal-mode diamond Raman laser enabled by suppressing parasitic stimulated Brillouin scattering
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-01-01 |
| Journal | High Power Laser Science and Engineering |
| Authors | Yuxuan Liu, Chengjie Zhu, Yuxiang Sun, Richard P. Mildren, Zhenxu Bai |
| Institutions | University of Chinese Academy of Sciences, Shanghai Institute of Optics and Fine Mechanics |
| Citations | 13 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Power Single-Longitudinal-Mode Diamond Raman Laser
Section titled âTechnical Documentation & Analysis: High-Power Single-Longitudinal-Mode Diamond Raman LaserâThis document analyzes the research paper âHigh-power free-running single-longitudinal-mode diamond Raman laser enabled by suppressing parasitic stimulated Brillouin scatteringâ and outlines how 6CCVDâs advanced MPCVD diamond materials and processing capabilities can support and extend this high-coherence laser technology.
Executive Summary
Section titled âExecutive SummaryâThis research successfully demonstrates a robust, high-power, single-longitudinal-mode (SLM) diamond Raman laser (DRL), confirming the critical role of high-purity CVD diamond in advanced photonics.
- High Power SLM Output: Achieved 20.6 W of continuous-wave (CW) SLM Stokes output at 1240 nm from a free-running DRL.
- High Efficiency: Demonstrated 30% optical-to-optical conversion efficiency (1064 nm pump to 1240 nm Stokes) with a slope efficiency of 51.3%.
- Ultra-Narrow Linewidth: Resolved the spectral linewidth of the CW SLM DRL for the first time using the DSHI technique, measuring 105 kHz at 20 W output.
- Material Requirement: Utilized a high-quality CVD single-crystal diamond (SCD, Type IIa, 7 x 2 x 2 mm3) as the gain medium.
- Stability Mechanism: Stable SLM operation was maintained by suppressing parasitic Stimulated Brillouin Scattering (SBS) through precise cavity length tuning and spatial mode selection (using the diamond edge as an aperture).
- Application Confirmation: The results strongly confirm the inherent SLM advantages of DRLs, positioning diamond as the premier material for compact, high-power, high-coherence laser systems required in quantum technology and coherent detection.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the experimental results, demonstrating the performance achieved using the CVD single-crystal diamond medium.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Stokes Output Power | 20.6 | W | Continuous Wave (CW) at 1240 nm |
| Pump Wavelength | 1064 | nm | SLM Yb fiber amplifier source |
| Stokes Wavelength | 1240 | nm | Raman shift |
| Optical-to-Optical Efficiency | 30 | % | Conversion from 1064 nm to 1240 nm |
| Slope Efficiency | 51.3 | % | Measured above the 31.5 W threshold |
| Stokes Spectral Linewidth | 105 | kHz | Measured at 20 W output using DSHI |
| Pump Spectral Linewidth | 60 | kHz | Measured at 69 W input using DSHI |
| Stokes Power Stability (RMS) | 1.8 | % | Over 1 hour (Average 19.03 W) |
| Diamond Material Type | Type IIa SCD | N/A | CVD-grown single crystal |
| Diamond Dimensions | 7 x 2 x 2 | mm | Used as the Raman gain medium |
| Pump Beam Waist Radius | 15 | ”m | Focused within the diamond crystal |
| Stokes Beam Waist Radius | 31 | ”m | Focused within the diamond crystal |
| Cavity Free Spectral Range (FSR) | 531.6 | MHz | Total optical length 564.33 mm |
Key Methodologies
Section titled âKey MethodologiesâThe successful demonstration relied on precise material selection and cavity engineering to manage high power and suppress parasitic nonlinear effects.
- Gain Medium Selection: A high-purity, CVD-grown single-crystal diamond (SCD, Type IIa) was used, cut for propagation along the <110> direction to maximize Raman gain.
- Resonator Design: A V-shaped standing-wave cavity was employed. This design minimizes intracavity pump resonance and reduces sensitivity to misalignment, crucial for high-power operation.
- Mode Matching: A telescope system and focus lens (f = 75 mm) were used to optimize the overlap between the pump (15 ”m waist) and Stokes (31 ”m waist) beams within the diamond.
- Polarization Control: A half-wave plate (HWP) adjusted the pump polarization parallel to the <111> axis of the diamond to access maximum Raman gain.
- Parasitic SBS Suppression: Stable SLM operation was achieved by delicately adjusting the cavity length and positioning the diamond crystal edge to act as an aperture. This spatial filtering suppressed higher-order spatial modes associated with parasitic Stimulated Brillouin Scattering (SBS), which otherwise destabilizes the SLM output at high power.
- Linewidth Characterization: The spectral linewidth was accurately measured using the long-delayed self-heterodyne interferometric (DSHI) technique, providing sub-MHz resolution necessary for high-coherence laser analysis.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe success of this high-power DRL hinges entirely on the quality and precise engineering of the CVD diamond material. 6CCVD is uniquely positioned to supply the necessary components to replicate, scale, and advance this research.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this high-coherence DRL research, 6CCVD recommends the following materials:
| Material Grade | Description | Relevance to DRL Application |
|---|---|---|
| Optical Grade SCD | High-purity, low-birefringence Single Crystal Diamond (SCD) with nitrogen concentration < 1 ppb (Type IIa equivalent). | Essential for minimizing absorption and scattering losses, maximizing the $\chi^{(3)}$ nonlinear gain required for efficient SRS and high-power scaling. |
| SCD Substrates | SCD plates up to 10 mm thick. | Provides the necessary bulk material for high-power applications where long interaction lengths (7 mm used here) are required to achieve high conversion efficiency. |
Customization Potential
Section titled âCustomization PotentialâThe paper highlights the need for extremely precise material dimensions and surface quality to manage beam waists and suppress parasitic effects. 6CCVD offers full customization to meet these stringent requirements:
- Custom Dimensions: 6CCVD provides custom plates and wafers up to 125 mm (PCD) and substrates up to 10 mm thick (SCD). We can supply the required 7 x 2 x 2 mm3 geometry, or larger dimensions for power scaling, using precision laser cutting.
- Ultra-Low Roughness Polishing: The stability of the SLM output is highly sensitive to intracavity parasitic etalon effects. 6CCVD guarantees an industry-leading surface finish of Ra < 1 nm for SCD, minimizing scattering losses and improving cavity Q-factor.
- Metalization Services: While the paper used AR coatings, future integrated DRL systems may require thermal management or electrical contacts. 6CCVD offers in-house metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu deposition, for advanced device integration.
- Global Logistics: We ensure reliable, global shipping (DDU default, DDP available) of high-value diamond components directly to your research facility.
Engineering Support
Section titled âEngineering SupportâThe suppression of parasitic SBS through precise cavity tuning and spatial mode selection is a complex engineering challenge. 6CCVDâs in-house PhD team specializes in the material science and optical properties of diamond for high-power applications.
We offer expert consultation on:
- Material Selection: Optimizing SCD grade and orientation (<110> vs. <100>) for specific Raman gain requirements.
- Thermal Management: Designing diamond components and mounting solutions to maintain the temperature stability (20°C used in the paper) crucial for minimizing Raman phonon frequency drift and ensuring long-term wavelength stability.
- Surface Preparation: Advising on the optimal polishing and surface treatment necessary to minimize scattering losses in high-finesse standing-wave resonators.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract A continuous-wave (CW) single-longitudinal-mode (SLM) Raman laser at 1240 nm with power of up to 20.6 W was demonstrated in a free-running diamond Raman oscillator without any axial-mode selection elements. The SLM operation was achieved due to the spatial-hole-burning free nature of Raman gain and was maintained at the highest available pump power by suppressing the parasitic stimulated Brillouin scattering (SBS). A folded-cavity design was employed for reducing the perturbing effect of resonances at the pump frequency. At a pump power of 69 W, the maximum Stokes output reached 20.6 W, corresponding to a 30% optical-to-optical conversion efficiency from 1064 to 1240 nm. The result shows that parasitic SBS is the main physical process disturbing the SLM operation of Raman oscillator at higher power. In addition, for the first time, the spectral linewidth of a CW SLM diamond Raman laser was resolved using the long-delayed self-heterodyne interferometric method, which is 105 kHz at 20 W.