Fringe-shifting interferometric laser lithography with optical nonlinearity for micro- and nanofabrications

The authors demonstrate an interferometric laser lithography process armed with a fringe-shifting technique, which utilizes nonlinear light-matter interaction. With this method, multiphoton-sensitive materials are ablated using ultrashort pulse interference fringes, enabling the ablated regions to be spaced by a fraction of the fringe pitch. For concept-proving experiments, confocal optics equipped with a diffractive beam splitter and a phase shifter are built to perform a fringe shift. This creates a phase difference between split beams that interfere with each other, producing high-contrast fringes. Precise control of beam intensity and beam phase is essential.