Pulsed Laser Diamond Machining for Transparent Graphite-Free Surfaces
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Solution Overview
Problem
Current laser machining techniques for diamonds result in surfaces that are not transparent and contain graphite, limiting their smoothness and commercialization potential, especially for engineering applications where transparency and graphite-free surfaces are required.
Innovation Solution
A method involving ultra-short pulsed laser machining in a liquid medium with controlled repetition frequency, circular or elliptical polarization, and the presence of a surfactant, which reduces graphite deposition and enhances surface smoothness and transparency without the need for post-treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser ablation is used to machine diamond, then machining speed and shape freedom are improved, but surface smoothness and transparency deteriorate due to graphite formation
Solution Approach 1:
The patent changes the laser pulse duration parameter to ultra-short pulses (femtosecond to picosecond range) and adjusts the repetition frequency to prevent thermal accumulation. This parameter change transforms the material removal mechanism from thermal ablation with graphite formation to a cleaner ablation process that maintains surface smoothness and transparency.
Solution Approach 2:
The patent employs periodic ultra-short laser pulses with controlled repetition frequency. The periodic action allows sufficient time between pulses for heat dissipation and prevents continuous thermal buildup that would cause graphite formation, while maintaining high machining efficiency through cumulative material removal.
2Length of stationary object
If conventional laser machining is used, then machining depth can be increased, but graphite deposition increases and surface transparency is lost
Solution Approach 1:
The patent uses ultra-short pulse duration (femtosecond to picosecond) combined with optimized repetition frequency to change the interaction mechanism between laser and diamond. This enables deep machining by accumulating material removal over many pulses without transitioning to thermal ablation that produces graphite, thus achieving deep transparent channels.
Solution Approach 2:
The patent replaces conventional thermal laser ablation with a cold ablation mechanism using ultra-short pulses. This substitution eliminates the thermal field that causes graphite formation, allowing deep machining through purely mechanical vaporization of diamond material without harmful byproducts.
3Manufacturing precision
If mechanical polishing is used to achieve transparency, then surface smoothness and transparency are improved, but machining time increases significantly
Solution Approach 1:
The patent replaces mechanical polishing with laser-based ablation using ultra-short pulses. The laser directly removes material at the desired depth and shape with precision, achieving transparent surfaces without the time-consuming mechanical polishing process. The cold ablation mechanism ensures no thermal damage or graphite formation that would require additional finishing.
Solution Approach 2:
The ultra-short pulse laser machining process is self-finishing, as the precise control of pulse energy and duration automatically produces smooth, transparent surfaces without requiring subsequent polishing operations. The process inherently achieves the final surface quality required for optical applications.
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 achieves transparent and smooth diamond surfaces without additional treatment, allowing for deeper machining depths while maintaining transparency and preventing graphite formation, thereby expanding the applications of laser-machined diamonds in physics experiments and other fields.
Implementation Method 1
a laser source is activated so as to apply it to the surface to be machined a laser beam having pulses of duration at most equal to one microsecond
Data Source
Figure 1~3
Figure 4~6
AI summary
To machine a diamond (2) using a pulsed laser, the diamond (2) is placed in a container (20) containing a transparent liquid (3). The liquid level is at least 100 microns above a surface of the diamond (2) to be machined, and said transparent liquid (3) can further contain a surfactant additive in an amount of at least 2% and 10% by mass. Next, a laser source (10) is activated such that a laser beam (1) 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 (2) and the laser source (10), cross-wise to the laser beam (1) and axially in depth, with an amplitude and orientations that are determined by the shape to be machined in the diamond (2).