Stimulated emission from nitrogen-vacancy centres in diamond

At a Glance

Metadata	Details
Publication Date	2017-01-27
Journal	Nature Communications
Authors	Jan Jeske, Desmond W. M. Lau, Xavier Vidal, Liam P. McGuinness, Philipp Reineck
Institutions	The University of Melbourne, ARC Centre of Excellence for Engineered Quantum Systems
Citations	91
Analysis	Full AI Review Included

Stimulated Emission in NV Centres: Enabling Diamond Lasers and Next-Generation Sensors

Technical Analysis and Solutions Briefing for 6CCVD Engineering

Executive Summary

This paper presents definitive experimental and theoretical evidence for stimulated emission (SE) in nitrogen-vacancy (NV) ensembles in diamond, establishing a key foundation for realizing NV-based diamond lasers and enhanced quantum sensors.

Core Achievement: First definitive observation of stimulated emission from NV^- ensembles using red light in the phonon sideband region (~700 nm).
Operational Window Defined: SE is shown to be the dominant process (over destructive photoionization) when stimulating wavelengths are greater than 650 nm. This directly enables tuneable phonon-sideband lasing.
Methodology: Utilized a dual-excitation setup: a 532 nm Continuous Wave (CW) green pump laser and a high-intensity, tunable 6 ps pulsed red laser, coupled with highly filtered detection.
Performance Metrics: Stimulated emission resulted in a measurable spontaneous emission reduction of 18% to 21% at the NV^- zero-phonon line (ZPL).
Temporal Dynamics: The recovery timescale of the excited state population varied with CW pump power, confirming the presence of stimulated decay rather than slower ionization recovery processes.
Future Applications: The results validate the feasibility of developing highly efficient, tuneable NV diamond lasers and new ultra-precise Laser Threshold Magnetometry sensors.

Technical Specifications

Hard data extracted from the research paper detailing the physical parameters and experimental outcomes.

Parameter	Value	Unit	Context
Material Used	Single Crystal Diamond (Type 1b)	-	High NV density required (via 2 MeV e^- irradiation).
NV^- Zero-Phonon Line (ZPL)	637	nm	Characteristic spontaneous emission peak.
NV⁰ Zero-Phonon Line (ZPL)	575	nm	Characteristic spontaneous emission peak.
Primary Pump Wavelength (CW)	532	nm	Green laser source (for initial excitation to ³E state).
Stimulating Wavelength (Pulsed)	~700	nm	Peak of the NV phonon sideband absorption spectrum.
Stimulation Pulse Duration	6	ps	Provided intense light field (Watts range).
Stimulation Repetition Rate	40	MHz	Corresponds to 25 ns period between pulses.
Ionization Threshold (Observed)	660	nm	Wavelength below which photoionization dominates SE.
Emission Reduction (NV^- ZPL)	18 to 21	%	Reduction in spontaneous emission due to SE at 700 nm.
Spontaneous Decay Rate (L₂₁)	65.3	MHz	Corresponds to 12 ns excited state lifetime.
Required Minimum NV Density	3.6	p.p.m.	Estimated minimum density required for lasing (high Finesse cavity).
Estimated Lasing Pump Power (P_thresh)	240	mW	Estimated for specific cavity (F=10⁵, 1 p.p.m. NV concentration).

Key Methodologies

The experimental approach relied on precise material engineering and sophisticated multi-wavelength optical control systems.

Diamond Preparation:
- Used Type 1b SCD samples (~500 µm and 50 µm thickness).
- Samples were irradiated with 2 MeV electrons (fluence up to 2 x 10¹⁸ e cm^-2) followed by high-temperature vacuum annealing (800 °C to 900 °C) to maximize high-density NV center formation.
Dual Laser Excitation:
- A CW 532 nm green laser (A_green) was used for continuous pumping of the NV ground state (³A₂) to the excited state (³E).
- A pulsed supercontinuum source (Fianium WL SC400-8) with a tunable filter provided the high-intensity red stimulating light (A_red(t)).
Wavelength Filtering and Detection:
- Detection relied on blocking the high-power pump (532 nm notch filter) and stimulating light (650 nm short pass filter) to monitor only the resulting spontaneous emission spectra (NV^- at 637 nm and NV⁰ at 575 nm).
Temporal Dynamics Measurement:
- Avalanche Photodiode (APD) and time-correlated counting (0.1 ns resolution) were used to analyze the sub-nanosecond emission reduction during the 6 ps pulse and the subsequent recovery (25 ns interval).
Direct Stimulated Emission Measurement:
- To isolate the directional stimulated emission signal from spontaneous noise, the green pump laser was modulated (548 Hz).
- The red stimulating light was changed to CW 705 nm.
- A lock-in amplifier was used to filter the detection signal to the modulation frequency, confirming the linear dependence of SE on red laser power.

6CCVD Solutions & Capabilities

This research proves the viability of using high-quality SCD for next-generation quantum technologies, specifically tuneable solid-state lasers and highly sensitive magnetometers. 6CCVD is uniquely positioned to supply the foundational diamond material required to replicate and advance this work.

Applicable Materials

Successful NV-based laser development requires tightly controlled nitrogen concentration, high crystal purity, and precise geometry—all specialized capabilities offered by 6CCVD’s MPCVD process.

Material Requirement in Research	6CCVD Material Solution	Engineering Rationale
High NV Density Precursor	Optical Grade SCD (Controlled N)	We supply high-purity Single Crystal Diamond (SCD) doped with precise Nitrogen concentrations during growth (Type IIa with controlled N doping) to facilitate high-yield post-processing (irradiation/annealing) for NV formation.
Controlled Charge States	Boron-Doped Diamond (BDD)	For fine-tuning Fermi levels and stabilizing NV^- charge states, we offer BDD films and plates, essential for optimized quantum applications.
Lasing Environment (Cavity)	Ultra-Low Roughness SCD Plates	The paper notes that lasing requires specific cavity integration. We provide SCD plates with polishing specified to Ra < 1 nm over large areas, ideal for direct integration with external mirror coatings or etched photonic structures.

Customization Potential

The integration of NV ensembles into complex devices like laser cavities demands custom dimensions, precise thickness control, and sophisticated surface modification.

Precision Diamond Dimensions: The study utilized thinner 50 µm SCD samples for transmission experiments. 6CCVD provides custom SCD thickness from 0.1 µm up to 500 µm, and substrates up to 10 mm thick, ensuring material fits strict resonator requirements.
Custom Geometric Machining: For integration into laser cavities or waveguides required for efficient collection (as discussed in related NV sensor studies), 6CCVD offers high-precision laser cutting and shaping services for custom geometries.
Integrated Metalization Services: Achieving the Finesse values (F = 10⁵) required for lasing involves high-reflectivity mirrors. 6CCVD offers in-house metalization (e.g., Au, Pt, Ti, W, Cu) essential for depositing contact pads, microwave structures, or integrated mirror coatings directly onto the diamond substrate.

Engineering Support

This research paves the way for commercial NV magnetometers based on laser threshold sensing, requiring specialized material knowledge.

Quantum Sensor Development: 6CCVD’s in-house PhD engineering team can assist clients in selecting optimal SCD purity and nitrogen concentration (pp.m. level control) for specific quantum sensing applications, such as ensemble NV magnetometry and laser threshold sensing.
Process Optimization: We consult on post-growth processing parameters, including electron/ion implantation strategies and annealing protocols, necessary to achieve the high, uniform NV center density required for high-contrast stimulated emission experiments.

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

Tech Support

Original Source

DOI: https://doi.org/10.1038/ncomms14000