Someone has come up with a method of engraving riblets on the surface of aircraft using laser interference patterns.

Riblets are (very) tiny grooves carved in the surface of an aircraft to reduce skin drag:

A process to automatically laser drag-reducing riblets onto the painted surfaces of aircraft has been developed by two German companies, laser surface treatment specialist 4JET and aircraft paint supplier Mankiewicz.

The Laser Enhanced Air Flow (LEAF) technology uses laser interference patterning to rapidly create fine streamwise grooves in the paint topcoat. These microscopic grooves, or riblets, have long been known to reduce viscous drag from turbulent flow over aircraft surfaces.

Riblets have been proven to reduce drag by up to 10%, for fuel savings on long-haul airliners of more than 1%, the companies say. Ways of exploiting this benefit have been previously developed, from covering the airframe with grooved plastic film to embossing riblets into the topcoat during painting. But issues from accessibility to durability have so far prevented adoption.

Removing paint using lasers is a well-known technology, but is too slow to create the high density of riblets required to achieve drag reductions, the companies say. Instead of creating the grooves line-by-line using a single laser spot, 4JET says it has developed a way to speed up the process by a factor of 500 using laser interference patterning.

The laser beam is split into two and recombined on the surface so that the light waves overlap in a controlled way. This superposition creates a pattern with dozens of equidistant lines with alternating high and low intensity within a single laser spot. This allows about 1 m³ (35 ft.³) of riblet area to be created in less than 1 min., the companies say.

Way to think outside of the box.