Laser "Engraving" PDC Diamonds: Conquering the Hardest Material with Light

Diamond is the hardest substance in nature, but it is not just a jewel. This material has thermal conductivity that is 5 times faster than copper, can withstand extreme high temperatures and radiation, can transmit light, insulate, and even be transformed into a semiconductor. However, it is these "superpowers" that make PDC diamonds the "most difficult to process" material—traditional tools either can't cut it or leave cracks. It wasn't until the emergence of laser technology that humans finally found the key to conquering this "king of materials".

Why Can Lasers "Cut" PDC Diamonds?

Imagine using a magnifying glass to focus sunlight to ignite paper; the principle of laser processing PDC diamonds are similar, but more precise. When a high-energy laser beam irradiates PDC diamonds, a microcosmic "carbon atom metamorphosis" occurs:

PDC diamonds transform into graphite

The laser energy transforms the surface structure of PDC diamonds (sp³) into the softer graphite (sp²), like a diamond instantly "devolving" into pencil lead.

Graphite is "evaporated"

The graphite layer sublimates at high temperature or is etched by oxygen, eventually leaving precise processing marks.

Key breakthrough: defects

Theoretically, perfect diamond can only be processed by ultraviolet laser (wavelength <229 nm), but in reality, artificial PDC diamond always has tiny defects (such as impurities, grain boundaries). These defects act like "loopholes", allowing ordinary green light (532 nm) or infrared laser (1064 nm) to be absorbed. Scientists can even manipulate the distribution of defects to "command" the laser to engrave specific patterns on PDC diamonds.

Laser Types: Evolution from "Furnace" To "Ice Blade"

Laser processing, combined with computer numerical control systems, advanced optical systems, and high-precision and automated workpiece positioning, can form research and production processing centers. Applied to PDC diamonds processing, it can achieve efficient, high-precision processing. Different types of laser beams acting on the surface of PDC diamonds result in significantly different processing effects. Lasers used in PDC diamonds processing are divided into "thermal processing" and "cold processing" based on the relationship between laser pulse length and atomic lattice collisions, with the most representative being nanosecond lasers and femtosecond lasers.

Microsecond laser processing

Microsecond laser pulses have a wider pulse width and are usually suitable for rough processing. Before the advent of mode-locking technology, most laser pulses were in the microsecond and nanosecond range. Currently, there are few reports on direct microsecond laser processing of PDC diamonds, and most of them focus on back-end processing applications.

Nanosecond laser processing

Nanosecond lasers currently occupy a large market share, with advantages such as good stability, low cost, and short processing time, and are widely used in enterprise production. However, the nanosecond laser ablation process causes thermal damage to the sample, manifesting as a large heat-affected zone during processing.

Picosecond laser processing

Picosecond laser processing lies between nanosecond laser thermal equilibrium ablation and femtosecond laser cold processing. The significantly reduced pulse duration greatly reduces the damage caused by the heat-affected zone.

Femtosecond laser processing

Ultrafast laser technology brings opportunities for fine processing of PDC diamonds, but the high cost and maintenance of femtosecond lasers limit the promotion of processing methods, and most related research currently remains at the laboratory stage. In femtosecond laser processing, the laser energy acts on the irradiated area through the photo-induced optical breakdown effect, where a large number of electrons are ionized, leading to changes in structure and phase composition. For PDC diamonds, this involves the transition from sp³ phase to sp² phase, followed by material ablation in the irradiated area.

From "unable to cut" to "engraving at will", laser technology has made PDC diamonds no longer a "vase" confined in the laboratory. With technological iterations, in the future we may see diamond chips dissipating heat in mobile phones, PDC diamonds storing information in quantum computers, and even PDC diamonds biosensor implanted in the human body... This dance between light and diamond is changing our lives.