Although metals are reflective to the fiber laser, it takes much less power (watts) for the one-micron wavelength laser to break through the reflectivity factor. Fiber lasers can create carbon migration marks with as little as 10 watts of power. Fiber lasers also have the ability to engrave or remove the metal from the surface. Some metals with little or no carbon can be darkened by melting/charring the metal with the fiber laser. It is also possible to get white marks on some metals with fiber lasers.
MOPA-style fiber lasers can produce some shades of color on a few types of metals. The color effect is cause by very specific control of how the metal is heated during marking. Color results are restricted to very small areas before the part starts to heat too much, causing the color to change. Color results can also vary considerably from one item to another. CerMark laser bonding coatings also work with fiber lasers as long as the laser system can be set to 200 kHz. or higher frequency.
-Mike Stover, Advanced Identification Inc.