Pulsed Laser Diamond Machining for Graphite-Free Transparent Cuts
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Solution Overview
Problem
Current laser machining techniques for diamonds fail to produce surfaces that are both smooth and graphite-free to the extent of being transparent without additional post-treatment, especially at significant depths, due to the generation of a graphitized layer and poor surface smoothness.
Innovation Solution
A method involving the use of a pulsed laser with ultra-short pulses and a surfactant-containing liquid, where the repetition frequency of the laser pulses is adjusted to be less than 5 kHz, and the diamond is machined in a liquid with a level above the surface to be machined, ensuring circular polarization and controlled scanning to achieve a smooth, graphite-free surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser ablation is used to machine diamond, then cutting speed and shape freedom are improved, but surface smoothness and transparency deteriorate due to graphite formation
Solution Approach 1:
The patent applies parameter changes by using ultra-short laser pulses (femtosecond to picosecond duration) instead of conventional longer pulses, and by operating at specific wavelengths (e.g., 515 nm green laser) to modify the interaction between laser and diamond material. This enables ablation with minimal heat diffusion, preventing graphite formation while maintaining high cutting speed and achieving transparent surfaces without post-treatment
Solution Approach 2:
The patent exploits phase transitions by controlling the laser-induced ablation process to directly vaporize diamond material without passing through a molten or graphitized state. The ultra-short pulse duration ensures that material is removed via direct sublimation or plasma formation, bypassing the graphitization phase that normally occurs with conventional laser processing, thus achieving clean, transparent surfaces
2Adaptability or versatility
If conventional laser machining is used, then cutting freedom is improved, but surface quality deteriorates requiring post-treatment
Solution Approach 1:
By changing the laser pulse duration to ultra-short scales (femtosecond/picosecond) and selecting specific wavelengths, the patent achieves a regime where material removal occurs without significant heat diffusion to surrounding areas. This prevents the formation of recast layers and graphite, producing surfaces that are immediately transparent and require no mechanical polishing or chemical etching post-treatment, thereby maintaining cutting shape freedom while eliminating additional manufacturing steps
3Productivity
If laser pulses with high repetition frequency are used, then machining speed is improved, but graphite deposition increases reducing surface transparency
Solution Approach 1:
The patent employs periodic ultra-short laser pulses with carefully controlled repetition frequencies. The key insight is that the pulse duration (femtosecond to picosecond) is so short that even at high repetition rates, the cumulative heat input between pulses remains below the threshold for graphite formation. The periodic action removes material cleanly through cumulative ablation while allowing heat dissipation between pulses, maintaining surface transparency at high machining speeds
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables direct deep cutting of diamonds with transparent surfaces without post-treatment, maintaining smoothness and preventing graphite deposition, allowing for transparent and smooth machined surfaces at depths greater than 1 micron.
Implementation Method 1
activating a laser source so as to apply to a surface of the diamond which is to be machined a laser beam having pulses of duration at most equal to one microsecond
Implementation Method 2
The liquid used in the receptacle contains a surfactant additive
Data Source
AI summary
A method of machining a diamond includes using a pulsed laser. The diamond is placed in a container containing a transparent liquid. The liquid level is at least 100 microns above a surface of the diamond to be machined, and the transparent liquid can further contain a surfactant additive in an amount of at least 2% and 10% by mass. Next, a laser source is activated such that a laser beam with pulse durations of no longer than one microsecond at a repetition frequency of no more than 5 kHz is applied to the surface to be machined, and relative scanning is performed between the diamond and the laser source, cross-wise to the laser beam and axially in depth, with an amplitude and orientations that are determined by the shape to be machined in the diamond.