Optical physicists at NASA’s Goddard Space Flight Center are developing a new ultrafast laser that is capable of firing pulses of light just 100 millionths of a nanosecond in duration. The laser could potentially revolutionize the way NASA technicians manufacture and ultimately assemble instrument components made of dissimilar materials. The femtosecond laser has already shown that it can effectively weld glass to copper, glass to glass, and drill hair-sized pinholes in different materials.
Now the group, led by optical physicist Robert Lafon, is expanding its research into more exotic glass, such as sapphire and Zerodur, and metals, such as titanium, Invar, Kovar, and aluminum — materials often used in spaceflight instruments. The goal is to weld larger pieces of these materials and show that the laser technology is effective at adhering windows onto laser housings and optics to metal mounts, among other applications.
With support from the Space Technology Mission Directorate’s Center Innovation Fund program, the group is also exploring the technology’s use in fabricating and packaging photonic integrated circuits, an emerging technology that could benefit everything from communications and data centers to optical sensors. Though they are similar to electronic integrated circuits, photonic integrated circuits are fabricated on a mixture of materials, including silica and silicon, and use visible or infrared light, instead of electrons, to transfer information.
Central to advancing applications is the laser itself. By virtue of its short pulses — measured at one quadrillionth of a second — an ultrafast laser interacts with materials in a unique way. The laser energy doesn’t melt the targeted material. It vaporizes it without heating the surrounding matter. As a result, technicians can precisely target the laser and bond dissimilar materials that otherwise couldn’t be attached without epoxies.
According to Lafon, it’s not possible to bond glass to metal directly. It needs the use of epoxy, which outgases and deposits contaminants on mirrors and other sensitive instrument components. This could be a serious application. The team wanted to get rid of epoxies. They have already begun reaching out to other groups and missions to see how these new capabilities might benefit their projects. Another important application is in the area of micromachining. The ability to remove small volumes of material without damaging the surrounding matter allows to machine microscopic features.
Microscopic features include everything from drilled, hair-sized pinholes in metals — an application the team already demonstrated — to etching microscopic channels or waveguides through which light could travel in photonic integrated circuits and laser transmitters. The same waveguides could allow liquids to flow through microfluidic devices and chips needed for chemical analyses and instrument cooling.
The team — between working on several of NASA’s high-profile laser communications projects, including the Laser Communications Relay Demonstration — plans to compile a library of micromachining and welding capabilities. Once they are able to demonstrate this capability reliably, they will attempt to apply it to existing challenges at Goddard. Initial research shows that this technology could be applied to a large number of projects across NASA.