Commercial femtosecond lasers are manufactured by placing the optics and their mounts on a substrate, which requires tight alignment of the optics. So is it possible to make femtosecond lasers entirely out of glass? Scientists at the Swiss Federal Institute of Technology in Lausanne have managed to do so with a laser no larger than the size of a credit card and easier to align, according to the latest issue of the journal Optics.
Image Scientists have fabricated a gigafemtosecond laser on a glass substrate.
Because glass is a stable material due to its lower thermal expansion than conventional substrates, the researchers said they chose glass as the substrate and used a commercial femtosecond laser to etch special grooves into the glass for precise placement of the laser's basic components. Even in micron-scale precision manufacturing, the grooves and the components themselves are not precise enough to achieve laser-quality alignment. In other words, the mirrors were not yet fully aligned, so at this stage, their glass device could not be used as a laser.
So, the researchers further designed the etching so that a mirror sits in a groove with a micromechanical bend that locally twists the mirror when the femtosecond laser is illuminated. After aligning the mirror in this way, they eventually created a stable, small-scale femtosecond laser.
Despite its small size, the laser has a peak power of about 1 kilowatt and emits pulses for less than 200 femtoseconds, a time so short that light cannot pass through human hair.
This method of permanently aligning free-space optics through laser-matter interaction is scalable to a wide variety of optical circuits with extreme alignment resolution down to the sub-nanometer scale.
