Periodic and aperiodic liquid crystal-polymer composite structures realized via spatial light modulator direct holography

In this work we present the first realization and characterization of two-dimensional periodic and aperiodic POLICRYPS (Polymer Liquid Crystal Polymer Slices) structures, obtained by means of a single-beam holographic technique exploiting a high resolution spatial light modulator (SLM). A first investigation shows that the gratings, operating in the Raman Nath regime, exhibit a morphology and a electro-optical behavior that are typical of the POLICRYPS gratings realized by two-beam interference holography

Thermoplasmonics with Gold Nanoparticles: A New Weapon in Modern Optics and Biomedicine

Thermoplasmonics deals with the generation and manipulation of nanoscale heating associated with noble metallic nanoparticles. To this end, gold nanoparticles (AuNPs) are unique nanomaterials with the intrinsic capability to generate a nanoscale confined light‐triggered thermal effect. This phenomenon is produced under the excitation of a suitable light of a wavelength that matches the localized surface plasmonic resonance frequency of AuNPs. Liquid crystals (LCs) and hydrogels are temperature‐sensitive materials that can detect the host AuNPs and their photo‐induced temperature variations. In this perspective, new insight into thermoplasmonics, by describing a series of methodologies for monitoring, detecting, and exploiting the photothermal properties of AuNPs, is offered. From conventional infrared thermography to highly sophisticated temperature‐sensitive materials such as LCs and hydrogels, a new scenario in thermoplasmonic‐based, next generation, photonic components is presented and discussed. Moreover, a new road in thermoplasmonic‐driven biomedical applications, by describing compelling and innovative health technologies such as on‐demand drug‐release and smart face masks with smart nano‐assisted destruction of pathogens, is proposed. The latter represents a new weapon in the fight against COVID‐19

Thermoplasmonics with Gold Nanoparticles: A New Weapon in Modern Optics and Biomedicine

Thermoplasmonics deals with the generation and manipulation of nanoscale heating associated with noble metallic nanoparticles. To this end, gold nanoparticles (AuNPs) are unique nanomaterials with the intrinsic capability to generate a nanoscale confined light‐triggered thermal effect. This phenomenon is produced under the excitation of a suitable light of a wavelength that matches the localized surface plasmonic resonance frequency of AuNPs. Liquid crystals (LCs) and hydrogels are temperature‐sensitive materials that can detect the host AuNPs and their photo‐induced temperature variations. In this perspective, new insight into thermoplasmonics, by describing a series of methodologies for monitoring, detecting, and exploiting the photothermal properties of AuNPs, is offered. From conventional infrared thermography to highly sophisticated temperature‐sensitive materials such as LCs and hydrogels, a new scenario in thermoplasmonic‐based, next generation, photonic components is presented and discussed. Moreover, a new road in thermoplasmonic‐driven biomedical applications, by describing compelling and innovative health technologies such as on‐demand drug‐release and smart face masks with smart nano‐assisted destruction of pathogens, is proposed. The latter represents a new weapon in the fight against COVID‐19

Dual-mode control of light by two-dimensional periodic structures realized in liquid-crystalline composite materials

We report on the realization of a 2D refractive structure consisting of a polymer-liquid-crystal polymer slice grid. Nematic liquid crystal microdomains are confined inside well-sculptured elliptical cavities; experimental investigation shows that the liquid crystal director lies in the plane of the structure and its orientation follows a preferred direction. The sample exhibits both an electro-optical and an all-optical response owing to a small percentage of photosensitive azo dye included in the structure. A double external control of the two-dimensional grating efficiency can indeed be operated either by an optical pump beam or by the standard technique of applying a suitable external voltage to the sample. © 2010 Optical Society of America

Thermodiffusive photorefractivity in liquid crystals

A breakthrough in the search for photorefractive materials occurred with the prediction and discovery of photorefractive liquid crystals (LC). Photorefractive LC solves two key problems: first, the voltage necessary to apply to the photorefractive material for realization of wave mixing is reduced from kilovolts to volts; and second, the modulation of the refractive index of the material can be as large as 0.2. The difference between the diffusion constants D+ and D- of photogenerated positive and negative ions is the reason for charge separation and space charge formation in the photoconductive LC

Surface-activated photorefractivity and electro-optic phenomena in liquid crystals

Surface-localized electromagnetic fields can induce strong reorientation of liquid crystals (LC\u27s), thus making it possible to observe a whole new class of opto-electronic phenomena. We show the feasibility of reorientation of a LC by a spatially inhomogeneous electric field localized on a photorefractive substrate. The modulation of the space-charge density in the plane of the photorefractive substrate generates a component of the electric field, which is normal to the LC layer. The drift of ions enforced by that field can result in a surface-charge modulation pattern that can become permanent owing to adsorption of ions at the boundaries of the LC cell. The obtained results present large fundamental and practical interest for the visualization of surface-localized electric fields and the development of new principles of optical information processing and storage. © 1998 Optical Society of America

Realization of particular liquid crystal cells for propagation and characterization of optical spatial soliton

We report on the design, fabrication process and characterization of liquid crystal cells for investigation of optical spatial solitons. Controlling of the director orientation at the input interface, as well as in the bulk, allows to obtain configurations that can produce distinct optical phenomena in a light beam propagating in the cell. For a particular director configuration, it is possible to produce two waves inside the nematic liquid crystal cell: the extraordinary and the ordinary one. With a different director configuration, the extraordinary wave only is obtained, which propagates inside the cell at an angle of more than 7 degrees with respect to the impinging wave vector direction. Under this peculiar configuration and by applying an external voltage, it is possible to have a good control of the propagation direction of the optical spatial soliton. (c) 2006 Optical Society of America

Orientational phenomena in liquid crystals on photorefractive substrates

The use of photorefractive liquid crystals (LC) and LC on photorefractive substrates for optical information processing applications is examined. The experiment used a homogeneously orientated nematic LC (NLC) sandwiched in a cell with hard anchoring of the director at the boundary layers. It was shown that the threshold value of the surface-localized electric field increases moderately, even if the field decreases inside the NLC exponentially. This makes the electrooptical phenomena in NLC possible under surface-localized influences