Nanoparticles in Aquaous Suspension for TunAble and Reconfigurable Optical Devices – NASTAROD

This project focuses on the study and development of Aqueous Colloidal Suspensions of anisotropic Nanoparticles (ACSN). These materials have unique electro-optical properties that have some similarities with those of liquid crystals (LC). For example in isotropic phase, the application of an external (electric or magnetic) field induces a strong optical anisotropy.
But looking closer, ACSN also have extremely interesting advantages compared to other LC technologies: low operating electric fields, significant induced birefringence and low scattering losses, rather insensitive to temperature, and no need for any alignment film. On the other hand, the LC technology remains totally compatible with the use of ACSN. The general aim of this project is to synthesize and formulate different ACSN with optimized physical and optical properties and to demonstrate that their use can produce technological breakthroughs in different optical applicative fields (optical communication networks, optical sensors, LASER, optical instrumentation, etc.) through exploiting their outstanding optical and physical properties and their low-cost technology. Basically, in these domains, many optical functions do not require high speed response times, for instance reconfiguration and restoration capabilities in optical communication networks usually operate at 50 ms, wavelength sweeping sources for Fiber Bragg Grating sensor have typical frequencies as low as few kHz, etc.
The first step consists in the synthesis and optimization of various kinds of anisotropic nanoparticles that will be of mineral (synthetic goethite or natural clays) or of polymeric nature. In a second step, aqueous colloidal suspensions of these nanoparticles will be formulated and their phase diagrams will be determined. Then, a detailed study of the electro-optic properties of the colloidal suspensions will be pursued. The relevant parameters as the field-induced birefringence, dichroism, optical losses, and response times will be measured as function of the suspensions physical properties. To understand the underlying mechanism responsible for the measured giant susceptibility to the electric field, we will take advantage of the synthesis of tailored micron size ellipsoids. Such sizes are particularly suitable for tracking the particle orientation in the applied electric field. This study will be performed by using electro-optical and tracking techniques successfully employed to examine liquid crystals and colloids. The colloidal suspensions that have the most interesting properties will then be selected and studied in order to evaluate their use for different possible applications. Several types of technologies underlying different applications will be considered: The first one is a spatial phase shifter for free space applications such as interferometer (Mach-Zehnder, Fabry-Perot) and optical delay lines. The performance of the ACSN will be analyzed with respect to the wavelength range, wavefront distortion, operating temperature range, phase shift stability, etc. The second kind of devices uses a higher level of technological integration. They are fibred devices, microstructured fibers to realize optical functions as tunable filter or tunable LASER, and also fibred polarization controllers. This final stage is crucial to establish and validate the different optical technologies fully compatible with ACSN.