Nanocomposite hybrid photonic media for remote point sensors

Holographic sol-gel monoliths: optical properties and application for humidity sensing

Sol-gel monoliths based on SiO2, TiO2 and ZrO2 with holographic colourful diffraction on their surfaces were obtained via a sol-gel synthesis and soft lithography combined method. The production was carried out without any additional equipment at near room temperature and atmospheric pressure. The accurately replicated wavy structure with nanoscale size of material particles yields holographic effect and its visibility strongly depends on refractive index (RI) of materials. Addition of multi-walled carbon nanotubes (MWCNTs) in systems increases their RI and lends absorbing properties due to extremely high light absorption constant. Further prospective and intriguing applications based on the most successful samples, MWCNTs-doped titania, were investigated as reversible optical humidity sensor. Owing to such property as reversible resuspension of TiO2 nanoparticles while interacting with water, it was proved that holographic xerogels can repeatedly act as humidity sensors. Materials which can be applied as humidity sensors in dependence on holographic response were discovered for the first time.

Multilayer metal/metal-oxide diffractive structure for photonic temperature sensing

We designed and fabricated multilayer metal/metal-oxide surface relief diffractive grating structures by growing alternating Pt and SnO(x) layers. Optical interrogation at 633 nm reveals the temperature dependence of their reflection and transmission diffractive effects. This function is explored here in the context of a remote, spatially localized, photonic temperature sensing operation, achieving sensitivity of 10% per °C for the zeroth-order in the transmission mode. The experimental demonstration is found to be in good agreement with the results of rigorous coupled wave analysis of the composite metal/metal-oxide element.

Diffractive optic sensor for remote-point detection of ammonia

Remote-point photonic sensors are fabricated and evaluated. They are based on nanocomposite thin films comprising NiCl(2) nanocrystals embedded in sol-gel silica matrix and are patterned using direct UV laser microetching techniques to form surface relief structures, which exhibit environment sensitive optical diffraction effects. A strong response to ammonia is detected via the alteration of diffraction efficiency of its orders upon exposure to the analyte. Detection of ammonia in the 2 ppm level with a typical response time of about 30 s in the ambient, 50% RH 20 degrees C, room environment is demonstrated.