Tailored light emission from color centers in nanodiamond using self-assembled photonic crystals

At a Glance

Metadata	Details
Publication Date	2022-10-06
Journal	Frontiers in Nanotechnology
Authors	Sachin Sharma, ASHISH ASHISH, Rajesh V. Nair
Institutions	Indian Institute of Technology Ropar
Citations	2
Analysis	Full AI Review Included

Executive Summary

This research demonstrates deterministic control over the spontaneous emission characteristics of Nitrogen-Vacancy (NV) centers embedded in nanodiamonds (NDs) using self-assembled Photonic Crystals (PCs).

Core Achievement: Successfully engineered the Local Density of Optical States (LDOS) at room temperature to tailor NV center emission intensity and lifetime.
Intensity Control: Achieved 63% suppression and 17% enhancement of NV center emission intensity at the photonic stopgap wavelength (667 nm).
Methodology: Utilized self-assembled colloidal PCs (polystyrene spheres) and two complementary measurement geometries (rear-side and front-side) to switch between suppression and enhancement.
Lifetime Modification: Measured changes in the NV center lifetime (T₂) were observed across a broad spectral range, confirming LDOS modification beyond the immediate stopgap.
Theoretical Consistency: The spectral redistribution of emission lifetime adheres to the fundamental Barnett-Loudon sum rule.
Engineering Significance: Provides a simple, scalable, and effective platform for manipulating the emission dynamics of solid-state quantum emitters without complex nanofabrication.

Technical Specifications

Parameter	Value	Unit	Context
Emitter Material	Nanodiamonds (NDs) with NV centers	N/A	Solid-state quantum emitter
ND Average Size	70	nm	Used for drop-casting onto PCs
NV Center Density	>300	centers	Per nanodiamond
PC Material	Polystyrene microspheres	N/A	Refractive Index (RI) 1.59
PC Lattice Constant (Sample A)	277	nm	Reference sample (off-resonant)
PC Lattice Constant (Sample B)	406	nm	Experimental sample (resonant)
Measured Stopgap Wavelength (Sample B)	667	nm	Coincident with NV Phonon Sideband (PSB)
Excitation Wavelength	532	nm	Frequency doubled Nd-YAG laser
Excitation Pulse Width	52	ps	Used for time-resolved measurements
Emission Intensity Suppression	63	%	Sample B, measured in rear-side geometry
Emission Intensity Enhancement	17	%	Sample B, measured in front-side geometry
Reference Lifetime (T₂)	22.4 ± 0.2	ns	Rear-side geometry, 660 nm
Suppressed Lifetime (T₂)	23.2 ± 0.4	ns	Sample B, rear-side geometry, 660 nm
Enhanced Lifetime (T₂)	20.3 ± 0.3	ns	Sample B, front-side geometry, 660 nm
Collection Numerical Aperture (NA)	0.10	N/A	Low NA used to minimize K-vector averaging

Key Methodologies

The spontaneous emission control was achieved through the integration of NV-containing nanodiamonds with self-assembled Photonic Crystals (PCs) and characterized using complementary optical setups.

Photonic Crystal Fabrication:
- PCs were fabricated using the colloidal self-assembly method.
- Monodisperse polystyrene microspheres (RI 1.59) were allowed to evaporate in a temperature-controlled environment.
- This process resulted in self-assembled structures exhibiting face-centered cubic (FCC) packing with lattice constants of 277 nm (Sample A) and 406 nm (Sample B).
Sample Preparation:
- Nanodiamonds (70 nm average size, containing >300 NV centers) were drop-casted onto the surface of the fabricated PCs.
- Sample A (445 nm stopgap) served as the off-resonant reference. Sample B (667 nm stopgap) was the resonant sample.
Reflectivity and Simulation:
- Reflectivity spectra were measured using a spectrophotometer and simulated using the Finite Difference Time Domain (FDTD) method (Lumerical).
- Simulations confirmed the stopgap positions (453 nm and 664 nm) were in good agreement with measured values (445 nm and 667 nm).
Emission Measurement Geometries:
- A home-built confocal emission setup was used, excited by a 532 nm laser.
- Rear-side Geometry (Suppression): Excitation beam passes through the substrate and PC before reaching the NDs. Emission is collected through the same path.
- Front-side Geometry (Enhancement): Excitation beam directly excites the NDs decorated on the PC surface. Emission is collected from the top surface.
Time-Resolved Emission (Lifetime) Measurement:
- A 532 nm pulsed laser (52 ps, 10 MHz) was used for excitation.
- Emission was collected via a low NA (0.10) objective to minimize angular averaging effects.
- Decay curves were fitted using a biexponential function, yielding T₁ (attributed to graphitic impurities) and T₂ (actual NV center lifetime).

Commercial Applications

The ability to precisely control the spontaneous emission rate and intensity of NV centers is critical for advancing quantum technologies and biophotonics.

Quantum Information Processing:
- High-Efficiency Single Photon Sources (SPS): Tailoring the LDOS to enhance the Zero Phonon Line (ZPL) emission rate and suppress the Phonon Sideband (PSB) is essential for creating indistinguishable photons, a requirement for linear optical quantum computing.
- Spin Readout Optimization: Faster spontaneous emission rates (reduced T₂) enable faster optical initialization and readout of the NV spin state, improving overall quantum gate speed.
Quantum Sensing and Metrology:
- Enhanced Signal-to-Noise Ratio (SNR): Controlling the emission intensity (enhancement) allows for improved detection sensitivity in NV-based magnetic and electric field sensors.
- Biomedical Imaging: NV centers are used as robust, non-photobleaching fluorescent markers. Enhancing the PSB emission (which coincides with the biologically transparent window, 650-850 nm) improves deep-tissue imaging contrast and signal strength.
Integrated Nanophotonics:
- On-Chip Quantum Devices: The use of self-assembled PCs provides a scalable, low-cost method for integrating quantum emitters into photonic circuits and waveguides, crucial for quantum network development.
- Charge State Dynamics Control: The demonstrated LDOS modification can be used to engineer the charge state dynamics (NV⁰ vs. NV^-) of the NV center, optimizing the emitter for specific applications (e.g., spin coherence vs. bright fluorescence).

View Original Abstract

The defect centers in solid-state materials especially the nitrogen-vacancy (NV) centers in diamond have shown a tremendous potential for their utilization in quantum technology applications. However, they exhibit certain drawbacks such as the feeble zero phonon line with huge phonon contribution and the higher lifetime values. Here, we present a novel approach to control the spontaneous emission from NV centers in nanodiamond using engineered self-assembled photonic crystals. Using two complimentary emission measuring geometries at room temperature, we show a 63% suppression and 17% enhancement of NV center emission intensity using photonic stopgap, supported with simulations. The emission rates are modified in a broad spectral range of NV center emission and are consistent with the Barnett-Loudon sum rule. The results are crucial for emerging quantum technologies using NV centers in diamond.

Tech Support

Original Source

DOI: https://doi.org/10.3389/fnano.2022.951988

References

2016 - Solid-state single-photon emitters [Crossref]
2018 - Material platforms for spin-based photonic quantum technologies [Crossref]
2018 - Quantum technologies with optically interfaced solid-state spins [Crossref]
2011 - Hybrid nanocavity resonant enhancement of color center emission in diamond [Crossref]
1996 - Sum rule for modified spontaneous emission rates [Crossref]
2019 - The fine structure of the neutral nitrogen-vacancy center in diamond [Crossref]
2005 - Spectral and angular redistribution of photoluminescence near a photonic stop band [Crossref]
2012 - Engineered quantum dot single-photon sources [Crossref]
2021 - The diversity of three-dimensional photonic crystals [Crossref]
2013 - The nitrogen-vacancy colour centre in diamond [Crossref]