Laser Bleaching could be used to mark LGD's

[Garry H (Cut Nut)]

This rather scientific paper describes some new technology.
Not sure if either link will open the paper - if not just search the title.
Below is the conclusion.
file:///C:/Users/hollo/OneDrive/Documents/Book/Synthetic%20diamonds/Permanent%20optical%20bleaching%20in%20HPHT-diamond%20via%20aggregation%20of%20C-%20and%20NV-centers%20excited%20by%20visible-range%20femtosecond%20laser%20pulses%20-%20ScienceDirect.pdf

https://www.researchgate.net/publication/363636403_Permanent_optical_bleaching_in_HPHT-diamond_via_aggregation_of_C-_and_NV-centers_excited_by_visible-range_femtosecond_laser_pulses

5. Conclusions In conclusion, multiple exposure of a HPHT diamond irradiated by 3-MeV e-beam and lowpressure annealed at 1200 °C till its red color, by 515-nm 0.3-ps laser pulses strongly focused in its bulk, in a number of patterns as a function of pulse energy and exposure time resulted in an array of bleached buried micro-regions. In striking contrast with the all previous observations for natural and synthetic diamonds, in this work FT-IR and UV-near-IR transmission microscopy indicated the reduction of C, A, NV , and NV centers in the bleached micro-regions. Roomtemperature 3D-scanning confocal PL micro-spectroscopy indicates the presence of NV , NV , H3 or H4 centers, with the reduced and increased depth-dependent PL intensity of the low- and high-aggregated centers, respectively, in the bleached regions regarding the unexposed material. Such photo-stimulated aggregation process was revealed to be two-photon one, apparently, occurring via direct or indirect UV-range photoexcitation of the low-aggregated centers. These experimental findings, demonstrating the new mechanism of direct laser writing of structurallyand color-modified micro-regions inside the diamond, open a way for laser technologies in expanding performance and tracing of synthetic diamonds.

 

[Karl_K]

Interesting, thanks for posting.
crossed laser is already being used to mark inside diamonds and works with all types.

 

[Karl_K]

Here is a better link to get the entire thing with no registration:

Permanent optical bleaching in HPHT-diamond via aggregation of C- and NV-centers excited by visible-range femtosecond laser pulses

Red-colored high-pressure, high-temperature synthesized (HPHT) diamond was exposed in its bulk in a number of patterns to millions of 0.3-ps, 515-nm l…

www.sciencedirect.com

 

[holeydonut]

Are people buying lab diamonds and then somehow removing the "LG" or "Laboratory Grown" etching on the girdle? Is this tech meant to prevent a proliferation of improper diamonds into the all-natural marketplace?

 

[Garry H (Cut Nut)]

Are people buying lab diamonds and then somehow removing the "LG" or "Laboratory Grown" etching on the girdle? Is this tech meant to prevent a proliferation of improper diamonds into the all-natural marketplace?

that sort of cheating is why there is a science of gem ID called Gemmology.
It has two mm's for a rare and unusual reason. The US tendency to adjust english actually made a mistake in this case

 

[Karl_K]

Are people buying lab diamonds and then somehow removing the "LG" or "Laboratory Grown" etching on the girdle? Is this tech meant to prevent a proliferation of improper diamonds into the all-natural marketplace?

There is a worry of it happening in particular on the second hand market.
De Beers uses crossed lasers* to mark their lab diamonds in a none removable way, but it makes them all si2 clarity.

* 2 laser beams are used and by themselves are not powerful enough to melt diamond but where the 2 beams come together it is powerful enough.