Micro-Machining of Diamond, Sapphire and Fused Silica Glass Using a Pulsed Nano-Second Nd -YVO4 Laser

At a Glance

Metadata	Details
Publication Date	2021-08-23
Journal	Optics
Authors	David Waugh, C. Dale Walton
Institutions	Coventry University, University of Hull
Citations	5
Analysis	Full AI Review Included

Technical Documentation & Analysis: MPCVD Diamond Micromachining

This document analyzes the research paper “Micro-Machining of Diamond, Sapphire and Fused Silica Glass Using a Pulsed Nano-Second Nd:YVO$_{4}$ Laser” to provide technical specifications and align 6CCVD’s advanced MPCVD diamond solutions with the requirements of high-precision laser surface engineering.

Executive Summary

This study successfully demonstrates the use of a cost-effective, frequency-tripled 355 nm nanosecond (ns) Nd:YVO$_{4}$ laser for high-quality micromachining of diamond, positioning ns-lasers as a viable alternative to expensive femtosecond systems for specific applications.

Superior Diamond Quality: Single Crystal Diamond (SCD) yielded the best results, producing extremely well-defined micrometre features with minimal debris, significantly outperforming sapphire and fused silica glass.
Cost-Effective Processing: The relatively inexpensive Nd:YVO$_{4}$ laser achieved processing quality competitive with femtosecond lasers for micrometre-scale diamond modification.
Threshold Fluence Determination: Threshold fluence ($F_{th}$) for diamond was accurately determined, ranging from 10 Jcm^-2 to 35 Jcm^-2, demonstrating a strong dependence on the cumulative effects of incident pulses.
Graphitization Mechanism: Laser-induced graphitization was identified as a key mechanism in diamond, enhancing UV absorption and optimizing the ablation process, leading to cleaner material removal.
Accumulative Modification: Surface modification was driven by accumulative effects, requiring high pulse counts (up to 50,000 pulses) to achieve stable, constant-area features.
Application Relevance: The findings support the implementation of high-quality MPCVD diamond in industrial applications requiring precise, cost-optimized micrometre-scale surface modification, such as microfluidics and grating fabrication.

Technical Specifications

The following hard data points were extracted from the experimental methodology and results concerning the laser processing of diamond material.

Parameter	Value	Unit	Context
Laser Type	DPSS Nd:YVO$_{4}$	N/A	Frequency tripled, nanosecond pulsed system
Laser Wavelength ($\lambda$)	355	nm	UV regime
Pulse Duration ($\tau$)	1.3	ns	Nanosecond pulse length
Pulse Repetition Frequency (PRF)	5	kHz	Standard processing rate
Incident Fluence Range ($F_{o}$)	11 to 74	Jcm^-2	Range used for surface modification arrays
Irradiance Range	24 to 106	GWcm^-2	Calculated peak irradiance
Focused Beam Spot Diameter ($\omega$)	~1	µm	Achieved using 15.29 mm focal length lens
Threshold Fluence ($F_{th}$) Range (Diamond)	10 to 35	Jcm^-2	Dependent on cumulative pulse number (1 to 50,000)
Diamond Sample Dimensions	45 x 25 x 0.54	mm	Material tested
Largest Modified Site (Diamond)	6.7 x 14.1	µm	Achieved at 50,000 pulses, 72 Jcm^-2

Key Methodologies

The experiment focused on direct-write laser surface modification using controlled parameters to induce accumulative material removal and determine threshold fluences.

Laser Setup: A frequency tripled 355 nm DPSS Nd:YVO$_{4}$ laser was used, operating at a fixed Pulse Repetition Frequency (PRF) of 5 kHz and a pulse duration of 1.3 ns.
Focusing: A Geltech Molded Glass Aspheric Lens (f = 15.29 mm, NA 0.16) was employed to achieve a tight beam spot diameter of approximately 1 µm on the material surface.
Fluence Variation: Incident fluence ($F_{o}$) was varied between 11 Jcm^-2 and 74 Jcm^-2 by adjusting the pumping diode current (3A-4A).
Sample Modification: Arrays of laser-modified sites were produced on diamond and sapphire by systematically varying the incident fluence (columns) and the number of incident pulses (rows, up to 50,000 pulses).
Line Processing: A single process line was irradiated over a 3 cm distance using a fluence of 50 Jcm^-2, 5 kHz PRF, and a traverse speed of 100 mms^-1 for qualitative assessment.
Threshold Calculation: The modified area diameter ($D$) was measured, and the threshold fluence ($F_{th}$) was derived using the Gaussian beam spot size equation: $D^{2} = 2\omega^{2} \ln(F_{o}/F_{th})$.
Characterization: Optical microscopy and Scanning Electron Microscopy (SEM) were used to analyze feature quality, debris formation, and evidence of material phase change (e.g., graphitization in diamond).

6CCVD Solutions & Capabilities

The research confirms that high-quality diamond is the optimal material for precise UV nanosecond laser micromachining. 6CCVD provides the necessary MPCVD diamond materials and customization services required to replicate and advance this research into industrial applications.

Applicable Materials

To achieve the high-quality, debris-minimal micromachining results demonstrated in this paper, researchers require high-purity, low-defect diamond material.

Optical Grade Single Crystal Diamond (SCD): This is the ideal material for replicating the best results. 6CCVD supplies high-purity SCD plates (Type IIa) with thicknesses ranging from 0.1 µm up to 500 µm. High crystalline quality is essential to ensure predictable multi-photon absorption and minimize internal defects that could lead to unpredictable cracking (as seen in fused silica).
Heavy Boron Doped Diamond (BDD): For applications requiring enhanced electrical conductivity alongside optical transparency or specific electrochemical properties, 6CCVD offers BDD films. Laser processing of BDD can be optimized for integrated micro-sensors or electrodes.
Polycrystalline Diamond (PCD) Wafers: For scaling up to larger area processing, 6CCVD offers PCD wafers up to 125 mm in diameter, providing a cost-effective platform for micrometre-scale features where the highest optical transparency is not strictly required.

Customization Potential

6CCVD’s in-house engineering capabilities directly address the needs of advanced laser processing research and industrial integration.

Requirement from Research	6CCVD Customization Capability	Technical Advantage
Custom Dimensions	Plates/wafers up to 125 mm (PCD) and custom SCD sizes. Substrates up to 10 mm thick.	Ensures material availability for large-scale industrial prototypes or specific device integration geometries.
Surface Quality	Ultra-low roughness polishing: Ra < 1 nm (SCD), Ra < 5 nm (Inch-size PCD).	Critical for UV laser processing to minimize scattering, ensure consistent fluence delivery, and maximize feature definition.
Post-Processing Integration	Internal metalization capabilities (Au, Pt, Pd, Ti, W, Cu).	Allows for the integration of laser-machined micro-features (e.g., gratings, microfluidic channels) with electronic contacts or bonding layers for lab-on-a-chip devices.
Thickness Control	SCD and PCD films available from 0.1 µm to 500 µm.	Precise thickness control is vital for optimizing waveguide fabrication and managing thermal effects during high-fluence ns-laser processing.

Engineering Support

The observed phenomenon of laser-induced graphitization in diamond, which enhances UV absorption, is a complex material science challenge. 6CCVD’s expert team is positioned to support engineers and scientists leveraging this effect.

6CCVD’s in-house PhD team can assist with material selection and optimization for similar Micromachining and High-Power UV Laser projects.
We provide consultation on selecting the optimal diamond grade (e.g., specific nitrogen content or crystallographic orientation) to control the graphitization process, ensuring enhanced absorption and efficient ablation rates.
We offer technical guidance on surface preparation and polishing techniques necessary to achieve the ultra-clean, debris-minimal results observed in the diamond samples.
Global shipping (DDU default, DDP available) ensures rapid and reliable delivery of custom diamond materials worldwide, supporting time-sensitive research and development cycles.

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

View Original Abstract

Optically transparent materials are being found in an ever-increasing array of technological applications within industries, such as automotive and communications. These industries are beginning to realize the importance of implementing surface engineering techniques to enhance the surface properties of materials. On account of the importance of surface engineering, this paper details the use of a relatively inexpensive diode-pumped solid state (DPSS) Nd:YVO4 laser to modify the surfaces of fused silica glass, diamond, and sapphire on a micrometre scale. Using threshold fluence analysis, it was identified that, for this particular laser system, the threshold fluence for diamond and sapphire ranged between 10 Jcm−2 and 35 Jcm−2 for a laser wavelength of 355 nm, dependent on the cumulative effects arising from the number of incident pulses. Through optical microscopy and scanning electron microscopy, it was found that the quality of processing resulting from the Nd:YVO4 laser varied with each of the materials. For fused silica glass, considerable cracking and deformation occurred. For sapphire, good quality features were produced, albeit with the formation of debris, indicating the requirement for post-processing to remove the observed debris. The diamond material gave rise to the best quality results, with extremely well defined micrometre features and minimal debris formation, comparative to alternative techniques such as femtosecond laser surface engineering.

Tech Support

Original Source

DOI: https://doi.org/10.3390/opt2030016

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