Hierarchical Fourier Surfaces via Broadband Laser Vectorial Interferometry

The ever-growingdemandfor submicrometer-structuredsurfaceswith hierarchicalfeaturesis guidedby efficientapplicationsin augmented/virtualreality, display technologies,and Fourieroptics, as well as for the developmentof multifunctionalplatformsfor biomedicine,sensors,and security.Amongall, Fouriersurfacesstill representa challenge.Indeed,the currenttechnologiesare mainlybased on multistepprocesseswhich involvelithographicmethodsand/orthermal/chemical/electricaltreatmentand often suffer in terms of losses due to their intrinsicbinary design. Herein,a broadbandlaser composedof close andhighly correlatedlines allows for the simultaneousphotoinscriptionof extremelyprecise hierarchicalFouriersurfacesviavectorialinterference.By simply setting the numberof lines, their amplitude,and polarization,the polychromaticlight enablesa high-fidelityencodingof multiplesinusoidalprofileswith nanometricspatial resolution.Beat phenomenathat arise in the bulk of the recordingmediumresult in the never-observedhierarchicalstructuringof the topography.Such an approach,unconventionalfor holographictechniqueswhere monochromaticityof light is a key element,providespromisingperspectivesfor thein situdesign of hierarchicalFouriersurfacesand the scale-upof customizedstructuredplatforms,besidesthe obviousadvantagesof the methodin terms ofscalability,reconfigurability,and tunability.