Microcavity platform for widely tunable optical double resonance
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2022-08-29 |
| Journal | Optica |
| Authors | Sigurd FlƄgan, Patrick Maletinsky, Richard J. Warburton, Daniel Riedel |
| Institutions | University of Basel, University of Calgary |
| Citations | 18 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Doubly-Resonant Diamond Raman Scattering
Section titled āTechnical Documentation & Analysis: Doubly-Resonant Diamond Raman Scatteringā6CCVD Reference: SCD-Raman-Microcavity-2021
Executive Summary
Section titled āExecutive SummaryāThis research demonstrates a highly effective platform for widely-tunable, cavity-enhanced Raman scattering using high-quality single-crystal diamond (SCD) membranes integrated into an open Fabry-Perot microcavity.
- Core Achievement: Demonstrated doubly-resonant enhancement of Raman scattering in SCD, achieving high quality factors ($Q_p \approx 300,000$) in the visible wavelength regime ($\sim 630$ nm).
- Material Innovation: Utilized SCD micromembranes (thickness $t_d \approx 756$ nm) exhibiting a slight, controlled thickness gradient ($0.17$ nm/Āµm) to enable in-situ tuning of the double-resonance condition.
- Tuning Capability: Achieved continuous tuning of the double-resonance condition over $0.85$ THz experimentally, with theoretical predictions suggesting mode-hop-free tuning over $72.2$ THz across the mirror stopband.
- Performance Metrics: Extracted a low Raman gain linewidth ($\delta \nu_R \approx 48.3$ GHz), indicating low strain in the SCD material, crucial for high-performance photonics.
- Future Potential: The platform predicts low lasing thresholds ($P_{th} \approx 188$ mW in the current setup, sub-mW with optimization), paving the way for universal, low-power, frequency-tunable diamond Raman lasers and frequency conversion tools.
- 6CCVD Value Proposition: 6CCVD specializes in the high-purity SCD material required for this research, offering custom thickness control, ultra-low surface roughness (Ra < 1 nm), and precise dimensional fabrication necessary for replicating and advancing these microcavity devices.
Technical Specifications
Section titled āTechnical Specificationsā| Parameter | Value | Unit | Context |
|---|---|---|---|
| Material Type | Single Crystal Diamond (SCD) | N/A | High-purity, (100)-cut micromembrane |
| Diamond Thickness ($t_d$) | $756$ | nm | Used for double-resonance condition |
| **Thickness Gradient ($ | \Delta t_d / \Delta x | $)** | $0.17 \pm 0.2$ |
| Pump Wavelength ($\lambda_{pump}$) | $630$ to $640$ | nm | CW narrowband tunable red diode laser |
| Raman Shift ($\Delta \nu_R$) | $39.914$ ($1331.4$ cm-1) | THz | Fixed optical phonon frequency in diamond |
| Pump Q-Factor ($Q_p$) | $297,000 \pm 500$ | N/A | Measured quality factor of the pump mode |
| Stokes Q-Factor ($Q_s$) | $6,650 \pm 50$ | N/A | Measured quality factor of the Stokes mode |
| Raman Mode Volume ($V_R$) | $109.85$ | ĀµmĀ³ | Calculated effective Raman mode volume |
| Predicted Lasing Threshold ($P_{th}$) | $187.5$ | mW | Calculated for current experimental parameters |
| Optimized $P_{th}$ (Loss-less) | $0.78$ | mW | Predicted with optimized geometry ($t_d = 3361$ nm) |
| Experimental Tuning Range | $0.85$ | THz | Continuous tuning demonstrated via lateral displacement |
| Predicted Tuning Range (Mode-Hop-Free) | $72.2$ | THz | Calculated maximum tuning range across stopband |
| Raman Gain Linewidth ($\delta \nu_R$) | $48.3 \pm 1.6$ | GHz | Indicates low strain in the SCD membrane |
Key Methodologies
Section titled āKey MethodologiesāThe experiment relies on precise material engineering and advanced cavity control to achieve the doubly-resonant condition.
- Substrate Fabrication: Fused silica substrates were prepared with Distributed Bragg Reflectors (DBR) coatings. Spherical micro-indentations (radius of curvature $\approx 10$ Āµm) were fabricated via CO2 laser ablation on one substrate to define the Gaussian resonator mode.
- SCD Membrane Preparation: High-purity, (100)-cut Single Crystal Diamond (SCD) was thinned via Inductively-Coupled Reactive-Ion Etching (RIE) and Electron-Beam Lithography (EBL) to create micromembranes ($\approx 756$ nm thick).
- Thickness Gradient Introduction: A slight thickness gradient was intentionally introduced during the thinning process to enable spectral tuning via lateral movement.
- Cavity Integration: The SCD membrane ($\approx 20 \times 20$ Āµm) was transferred and integrated into the Fabry-Perot microcavity using a micromanipulator.
- In-Situ Tuning: Piezoelectric nanopositioners (attocube ANPx51, ANPz51) were used to control both the mirror separation ($t_a$) and the lateral position of the cavity mode relative to the SCD membrane.
- Double Resonance Establishment: The mirror separation and lateral position were tuned simultaneously to ensure that both the pump wavelength ($\lambda_{pump}$) and the red-shifted Stokes wavelength ($\lambda_R$) were resonant with distinct cavity modes ($q_{eff}=17$ and $q_{eff}=19$, respectively).
- Characterization: Cavity transmission, reflection, and emission spectra were measured using a narrowband diode laser and a single photon counting module to verify the double resonance and extract Q-factors.
6CCVD Solutions & Capabilities
Section titled ā6CCVD Solutions & Capabilitiesā6CCVD is uniquely positioned to supply the critical diamond materials and precision fabrication services required to replicate and advance this cutting-edge research in quantum and nonlinear optics.
Applicable Materials
Section titled āApplicable MaterialsāTo replicate the high Q-factors and low strain required for doubly-resonant Raman scattering, researchers need the highest quality diamond.
- Optical Grade Single Crystal Diamond (SCD): This is the explicit material used in the paper. 6CCVD provides high-purity, low-strain SCD substrates and membranes, essential for minimizing Raman gain linewidth ($\delta \nu_R$) and maximizing Q-factors.
- Custom SCD Thicknesses: The paper utilized membranes around $756$ nm. 6CCVD offers precise thickness control for SCD wafers and membranes from $0.1$ Āµm up to $500$ Āµm, allowing researchers to explore optimized geometries (e.g., the predicted optimal $t_d = 3361$ nm for sub-mW thresholds).
Customization Potential
Section titled āCustomization PotentialāThe success of this platform hinges on precise dimensional control and surface quality, areas where 6CCVD excels.
| Requirement from Paper | 6CCVD Capability | Technical Advantage |
|---|---|---|
| Membrane Dimensions ($20 \times 20$ Āµm) | Custom laser cutting and dicing services. | We provide plates/wafers up to $125$ mm (PCD) and custom-cut SCD membranes to exact specifications. |
| Thickness Control ($t_d \approx 756$ nm) | SCD thickness control from $0.1$ Āµm to $500$ Āµm. | Enables exploration of optimized geometries (e.g., $t_d = 3361$ nm) for lower lasing thresholds. |
| Surface Quality ($\sigma_q \approx 0.3$ nm simulated) | Ultra-Polishing Services. | Guaranteed surface roughness of Ra < 1 nm for SCD, significantly reducing surface scattering losses and improving Q-factors. |
| Future Device Integration | Custom Metalization. | 6CCVD offers in-house deposition of Au, Pt, Pd, Ti, W, and Cu, enabling direct integration of electrical contacts or reflective layers onto the diamond surface for advanced device architectures. |
| Thickness Gradient | Controlled Material Uniformity. | While the paper exploited a gradient, 6CCVD can provide either ultra-uniform SCD (for external tuning) or discuss controlled, intentional thickness variation for specific in-situ tuning applications. |
Engineering Support
Section titled āEngineering SupportāThe complexity of achieving the double-resonance condition and optimizing the Raman mode volume ($V_R$) requires deep material expertise.
- 6CCVDās in-house PhD team can assist with material selection and specification for similar Cavity Quantum Electrodynamics (CQED) and Nonlinear Optics projects.
- We provide consultation on how material properties (e.g., strain, surface roughness, crystallographic orientation) impact critical performance metrics like Q-factor and predicted lasing threshold ($P_{th}$).
- Our global shipping network (DDU default, DDP available) ensures rapid and reliable delivery of custom diamond materials worldwide, accelerating your research timeline.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Tunable open-access Fabry-Perot microcavities are versatile and widely applied in different areas of photonics research. The open geometry of such cavities enables the flexible integration of thin dielectric membranes. Efficient coupling of solid-state emitters in various material systems has been demonstrated based on the combination of high quality factors and small mode volumes with a large-range in situ tunability of the optical resonance frequency. Here, we demonstrate that by incorporating a diamond micromembrane with a small thickness gradient, both the absolute frequency and the frequency difference between two resonator modes can be controlled precisely. Our platform allows both the mirror separation and, by lateral displacement, the diamond thickness to be tuned. These two independent tuning parameters enable the double-resonance enhancement of nonlinear optical processes with the capability of tuning the pump laser over a wide frequency range. As a proof of concept, we demonstrate a <mml:math xmlns:mml=āhttp://www.w3.org/1998/Math/MathMLā display=āinlineā> <mml:mrow class=āMJX-TeXAtom-ORDā> <mml:mo>></mml:mo> </mml:mrow> <mml:mrow class=āMJX-TeXAtom-ORDā> <mml:mi mathvariant=ānormalā>T</mml:mi> <mml:mi mathvariant=ānormalā>H</mml:mi> <mml:mi mathvariant=ānormalā>z</mml:mi> </mml:mrow> </mml:math> continuous tuning range of doubly resonant Raman scattering in diamond, a range limited only by the reflective stopband of the mirrors. Based on the experimentally determined quality factors exceeding 300,000, our theoretical analysis suggests that, with realistic improvements, a <mml:math xmlns:mml=āhttp://www.w3.org/1998/Math/MathMLā display=āinlineā> <mml:mrow class=āMJX-TeXAtom-ORDā> <mml:mo>ā¼</mml:mo> </mml:mrow> <mml:mrow class=āMJX-TeXAtom-ORDā> <mml:mi mathvariant=ānormalā>m</mml:mi> <mml:mi mathvariant=ānormalā>W</mml:mi> </mml:mrow> </mml:math> threshold for establishing Raman lasing is within reach. Our findings pave the way to the creation of a universal, low-power frequency shifter. The concept can be applied to enhance other nonlinear processes such as second harmonic generation or optical parametric oscillation across different material platforms.