Nanocomposite-based Stretchable Optics
The integration of diffractive optical elements on stretchable substrates opens the way to therealization of a completely novel class of stretchable photonics systems, characterized by the ability of changing their optical properties upon modification of their shape due to tensile or compressive strain and to be highly conformable to complex surfaces. The interest in such devices is tremendously increasing driven by the need of bio-mimicking adaptive optical devices. Several attempts have been already made to fabricate stretchable diffracting optical elements by depositing reflective metallic films on gratings embossed on PDMS.
The bad adhesion of the metallic layer degraded the optical quality of the diffraction grating even upon a very small deformation. Here I present an effective approach to the fabrication of diffractive stretchable optical components, based on Supersonic Cluster Beam Implantation (SCBI) . Stretchable diffraction gratings can be obtained by replicating the structured surface of a rigid grating on PDMS . The optically active side is then implanted with silver nanoparticles by means of SCBI, in order to create a nanocomposite reflective layer with a thickness of tenths of nanometers. The superior resilience upon deformation of the silver-PDMS nanocomposite allows to maintain extremely good optical performance upon substantial deformation of the grating and a large number of deformation cycles.
The nanocomposite-based reflective optical devices were characterized both morphologically and optically showing excellent performances and stability compared to similar devices fabricated with standard techniques. The nanocomposite-based devices can be therefore applied to arbitrary curved non-optical grade surfaces in order to achieve optical power and to minimize aberrations like astigmatism. As a proof-of-principle a low-cost scanning spectrometer based on a stretchable diffraction grating is experimentally demonstrated and characterized .
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