Interactions of Atomistic Nitrogen Optical Centers during Bulk Femtosecond Laser Micromarking of Natural Diamond

At a Glance

Metadata	Details
Publication Date	2023-01-29
Journal	Photonics
Authors	Elena Rimskaya, G. Yu. Kriulina, Evgeny V. Kuzmin, S. I. Kudryashov, П. А. Данилов
Institutions	P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Lomonosov Moscow State University
Citations	4
Analysis	Full AI Review Included

Technical Documentation & Analysis: Bulk Femtosecond Laser Micromarking in Diamond

Executive Summary

This research demonstrates a highly controlled method for creating three-dimensional (3D) photoluminescent micromarks within the bulk of diamond using femtosecond (fs) laser inscription. This technology is critical for next-generation quantum and micro-electrooptical devices.

Core Achievement: Successful 3D structural patterning in bulk diamond (125 µm depth) using 515 nm, 0.3 ps fs laser pulses.
Mechanism: Laser irradiation drives the transformation of highly aggregated nitrogen centers (A, B1, B2) into low-aggregated optical centers (NV⁰, NV^-, H3, H4, N3a, N3b) via vacancy-mediated dissociation and aggregation.
Control Parameters: Micromark length and brightness are precisely controlled by varying incident pulse energy (0.1-1.6 µJ) and exposure time (10-240 s).
Predictable Yield: NV center formation exhibits saturation at pulse energies exceeding 1.0 µJ, enabling predictable color center density for device fabrication.
Material Requirement: The process relies heavily on the initial distribution and concentration of nitrogen impurities, highlighting the need for high-quality, nitrogen-controlled SCD material for industrial replication.
Application: Opens new technological opportunities for direct laser writing of 3D micro-electrooptical and photonic devices, including integrated quantum circuits and track-and-trace systems.

Technical Specifications

The following hard data points were extracted from the experimental methodology and results:

Parameter	Value	Unit	Context
Laser Wavelength	515	nm	Femtosecond pulse source (Visible range)
Pulse Duration	0.3	ps	Sub-picosecond regime
Pulse Energy Range	0.1 - 1.6	µJ	Micromark writing regime
Repetition Rate	100	kHz	Laser exposure frequency
Focusing Objective	0.25	NA	Micro-objective used for focusing
Inscription Depth (z)	~125	µm	Bulk inscription focal plane
Exposure Time Range	10 - 240	s	Variable exposure time (up to 24M pulses)
NV Formation Saturation	> 1.0	µJ	Pulse energy threshold for constant brightness
Characterization Excitation 1	405	nm	PL microspectroscopy (Blue excitation)
Characterization Excitation 2	532	nm	PL microspectroscopy (Green excitation)
Initial [A(2N)] Concentration	~175	ppm	Average nitrogen impurity concentration in natural IaAB sample
Micromark Depth Range	30 - 177	µm	Observed range of NV^- micromark formation (at 1.6 µJ)

Key Methodologies

The experiment utilized a combination of ultrashort pulse laser inscription and advanced 3D confocal spectroscopy to analyze the resulting structural modifications.

Material Characterization: Initial natural IaAB-type diamond was characterized using FT-IR, optical transmission spectroscopy, and 3D confocal Raman/PL microspectroscopy to determine the high concentration and aggregation state of nitrogen centers (A, B1, B2).
Femtosecond Laser Inscription: A Satsuma laser workstation delivered 515 nm, 0.3 ps pulses at 100 kHz. The beam was focused into the bulk of the diamond (z ~ 125 µm) using a 0.25 NA objective.
Parameter Matrix: Micromarks were created across a matrix of variable pulse energies (0.1 µJ to 1.6 µJ) and exposure times (10 s to 240 s).
3D Confocal PL Analysis: Micromarks were analyzed at room temperature (25 °C) using 3D confocal PL microspectroscopy with two distinct excitation wavelengths (405 nm and 532 nm) to differentiate between various nitrogen-vacancy related centers (NV⁰, NV^-, H3, H4, N3a, N3b).
Internal Standard Correction: PL spectra intensity was corrected for depth-dependent confocal effects by normalizing the entire spectrum to the intensity of the diamond Raman line, ensuring accurate comparison across the bulk.
Center Transformation Analysis: Detailed spectral analysis confirmed complex transformations, including low-energy aggregation (e.g., A(N-N) + V → H3) and high-energy dissociation/vacancy-driven detachment (e.g., H4 → N3 + NV).

6CCVD Solutions & Capabilities

The successful replication and scaling of this 3D bulk micromarking technology—essential for integrated quantum and photonic devices—requires diamond material with superior purity, homogeneity, and precise nitrogen control, capabilities inherent to 6CCVD’s MPCVD growth process.

Applicable Materials for Replication and Scaling

The natural IaAB diamond used in this study suffers from inherent variability and high concentrations of uncontrolled nitrogen aggregates. To achieve predictable, high-yield NV center formation, researchers require nitrogen-controlled Single Crystal Diamond (SCD).

6CCVD Material Recommendation	Rationale for Application
Optical Grade SCD (Nitrogen-Controlled)	Provides superior crystalline purity and homogeneity compared to natural diamond, minimizing background defects and ensuring uniform laser interaction. We offer precise control over initial nitrogen incorporation (e.g., [N] < 1 ppm up to 100s ppm) to optimize the starting material for subsequent NV center creation.
High-Purity SCD	Ideal for applications requiring minimal background luminescence, allowing for sharper contrast between the laser-written micromarks and the surrounding bulk material.
Polycrystalline Diamond (PCD)	For large-area, non-quantum applications requiring robust bulk marking, 6CCVD offers PCD plates up to 125 mm in diameter, allowing for industrial scale-up of 3D marking processes.

Customization Potential for Advanced Photonics

6CCVD’s advanced manufacturing capabilities directly address the engineering challenges of scaling 3D diamond photonics:

Custom Dimensions and Thickness: The paper demonstrates marking at 125 µm depth. 6CCVD provides SCD plates with precise thickness control from 0.1 µm up to 500 µm, and substrates up to 10 mm thick, enabling optimization for specific focal depths and device geometries.
Large-Area Processing: We offer large-format PCD wafers up to 125 mm in diameter, facilitating the transition of bulk micromarking from laboratory samples (2.3 mm radius) to commercial-scale integrated circuits.
Surface Quality: For high-NA focusing and minimal scattering, surface quality is paramount. 6CCVD guarantees ultra-low roughness polishing: Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD.
Integrated Metalization: If the resulting micro-electrooptical devices require electrical contacts or waveguides, 6CCVD offers in-house metalization services, including Au, Pt, Pd, Ti, W, and Cu deposition, directly integrating the material preparation and device fabrication steps.

Engineering Support

The complex chemical transformations (low-energy aggregation, high-energy dissociation, and vacancy-driven detachment) detailed in the paper require expert material selection.

6CCVD’s in-house PhD team specializes in CVD diamond growth kinetics and defect engineering. We can assist researchers and engineers in selecting the optimal starting material (e.g., specific nitrogen concentration and aggregation state) to maximize the yield and spectral purity of desired color centers (NV, H3, H4) for similar Femtosecond Laser Micromarking projects.

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

View Original Abstract

Micromarks were formed in bulk natural IaAB-type diamond laser-inscribed by 515 nm 0.3 ps femtosecond laser pulses focused by a 0.25 NA micro-objective at variable pulse energies in sub-picosecond visible-range laser regimes. These micromarks were characterized at room temperature (25 °C) by stationary 3D confocal photoluminescence (PL) microspectroscopy at 405 nm and 532 nm excitation wavelengths. The acquired PL spectra exhibit the increasing pulse-energy-dependent yield in the range of 550-750 nm (NV0, NV− centers) at the expense of the simultaneous reciprocal reduction in the blue-green (490-570 nm, H-band centers) PL yield. The detailed analysis indicates low-energy intensity rise for H-band centers as an intermediate product of vacancy-mediated dissociation of B1 and B2 centers, with H4 centers converting to H3 and NV centers at higher pulse energies, while the laser exposure effect demonstrates the same trend. These results will help solve the problem of direct laser writing technology, which is associated with the writing of micromarks in bulk natural diamond, and promising three-dimensional micro-electrooptical and photonic devices in physics and electronics.

Tech Support

Original Source

DOI: https://doi.org/10.3390/photonics10020135

References

2017 - Laser writing of coherent colour centres in diamond [Crossref]
2019 - Femtosecond laser written photonic and microfluidic circuits in diamond [Crossref]
2016 - Diamond photonics platform enabled by femtosecond laser writing [Crossref]
2019 - Laser writing of individual nitrogen-vacancy defects in diamond with near-unity yield [Crossref]
2021 - Broadband and fine-structured luminescence in diamond facilitated by femtosecond laser driven electron impact and injection of “vacancy-interstitial” pairs [Crossref]