Laser inscription, a relatively new technology refers to a very small graphic or text being inscribed on the girdle of a diamond. The inscription is commonly a brand name, certificate number with laboratory name and/or a romantic message. The inscription is only visible with a jeweller's loupe, and even then can be difficult to read.
Prior to laser inscription, sealing diamonds in plastic packets was a popular way to prove that the diamond matched the certificate. Nowadays, a grading laboratory can laser inscribe the certificate number on the diamond's girdle, providing even more security over the sealing method.
However, it should be noted that laser inscription is not entirely fool proof. As Fred Cuellar explains:
Equipment used to laser inscribe diamonds can cost up to US$300,000. This is reflected in the extra cost charged by grading laboratories to do laser inscriptions. Manufacturers of laser inscription equipment include TeoSys and PhotoScribe.
Hot vs Cold Lasers
There are two types of laser inscription, commonly termed "hot" and "cold". Cold lasers operate with a lower wavelength (eg 193 nanometers) and hot lasers operate with a higher wavelength.
"Hot" lasers make it a lot easier to damage a diamond, as this article explains:
However, as the manufacturer of "cold" laser inscription equipment admits, "cold" laser inscription equipment can still damage a diamond if the laser is focused on one spot for a long enough time.
Real Life Examples
Below are some examples of laser inscription:
As you can see, "cold" laser inscriptions can be difficult to see, especially under frosted girdles.
Where To Get Your Diamond Laser Inscribed
Most international labs such as the GIA, EGL and HRD have laser inscription services. In Australia, the DCLA offers "cold" laser inscription services.