Interferometric femtosecond laser processing for nanostructuring inside thin film

Femtosecond laser interactions inside transparent dielectric films of refractive index, n(film), with tight focusing presents strong nonlinear interactions that can be preferentially confined at the fringe maxima as formed by Fabry-Perot interference, to generate thin nanoscale plasma disks separated on half-wavelength,lambda/2n(film). The nano-thin disk explosions can be controlled inside the film to cleave open subwavelength internal cavities at single or multiple periodic depths at low laser exposure, while higher exposure will eject a quantised number of film segments with segment thickness defined by the laser wavelength. This new method enables high-resolution film patterning for ejecting nanodisks at quantised film depth for colouring and three-dimensional (3D) surface structuring, as well as for fabrication of free-standing nanofilms.