Femtosecond Laser Structuration for Functionalization of Optical Windows – LAST_FLOW

We propose to investigate the possibilities of femtosecond (fs) laser ablation to design a new architecture of multifunctional optical surface. This technique is extremely promising since it has the advantage of being a one-step technology able to directly structure planar and non-planar surfaces of any kind of materials, with varying feature parameters.
Fs-laser machining has been used to create matrices of hole-like surface microstructures, in single or multiple hard surface layers, leading to the possibility to realize meta-surfaces allowing to build flat components having complex optical effects. Such architecture could provide antireflective and superhydrophobic properties.
The main objective is to develop a technological process based on fs-laser ablation to design sub-wavelength structures on optical substrates such as silicon and germanium, for MWIR and LWIR applications respectively. Other materials, like sapphire and diamond, will also be addressed. Furthermore, a Laser Induced Periodic Surface Structures process, allowing to attain nano-structures far below the size of the laser focus, will be envisaged to target the critical dimensions for applications in the visible range on glass material.
The challenge lies in the conception and validation of a laser surface patterning platform for the realization of a dense array of high aspect-ratio ~1µm-scale holes, in single or multiple-layered surface. Once the feasibility demonstrated, the aim is to upscale the capacity of the structuration process and to move towards an ultrafast laser patterning platform of curved surfaces.
In a first step, it is planned to address the structuration of 2” optical windows, as typically implemented in binoculars developed by Thales for Vis or IR bands. This achievement will then consist in the realization of a first demonstrator. As a final challenge, larger sizes (4’’) and non-planar windows shapes will be targeted, allowing applications on a larger scope of Thales systems.