Volume 7, Issue 5 - Optical Materials Part 2 / Guest Editors: Younès Messaddeq, Tigran Galstian and Réal Vallée

We present a review of polymer-liquid crystal-based devices for optical applications. Starting from a particular fabrication technique, which enables to obtain the POLICRYPS (POlymer LIquid CRYstal Polymer Slices) structure, we illustrate different realizations, along with their working principle and main features and performances. The name POLICRYPS indicates a structure made of parallel slices of pure polymeric material alternated to films of well-aligned nematic liquid crystal (NLC), with a spatial periodicity that can be settled in the range 0.2÷15 μm. Suitably designed samples can be utilized as optical devices with a high efficiency, which can be switched on and off both by applying an electric field of a few V/μm or by irradiating samples with a suitable light beam. In different geometries, POLICRYPS can be specialized to operate as switchable diffraction grating, switchable optical phase modulator, switchable beam splitter, or tunable Bragg filter. The POLICRYPS framework can be also used as a soft matter template for aligning different types of LCs or to create an array of tunable microlasers. Finally, we present a POLICRYPS structure with a polar symmetry of the director alignment, which enables local shaping of light polarization, allowing to convert circularly polarized beams into cylindrical vector beams.

Laser-induced glass processing has led to huge progress and applications over the last two decades. Here, we review recent advances in femtosecond laser-induced photochemistry in isotropic transparent oxide glasses specifically tailored with silver photoactive agents. The understanding of the influence of the considered glass matrix on the nature and properties of the created silver species is of prime importance. After presenting the key material properties, the formation mechanisms of laser-induced silver-based species are discussed, and potential technological applications are highlighted. Laser-induced processing of silver-containing oxide glasses paved the way for the fabrication of complex integrated waveguides and optical circuits with innovative fluorescent, nonlinear optical, and plasmonic properties. The universality of the method is expected to extend in any glass material that shows a similar laser-induced behavior in terms of silver cluster production.

This paper reports the formation of laser-induced periodic surface structures (LIPSS) observed on the ablated surface of bulk As 2 S 3 chalcogenide glasses produced after irradiation by a focused beam of femtosecond Ti:sapphire (fs)-laser (1 kHz, 100 fs, 800 nm). By controlling the irradiation condition of fs-laser, high spatial frequency LIPSS (HSFL) ripples parallel to polarisation of the incident light are formed. Nanovoids with an average diameter of ~300 nm and depth of 200 nm also appear between the ripples. Furthermore, we show a transition from the HSFL features toward the formation of low-spatial-frequency LIPSS (LSFL) with an intermediated complex structure of ripples, which are oriented simultaneously parallel and perpendicular to the polarisation of the incident light that we call cross-superposed LIPSSs.

Highly nonlinear gain media that are optically pumped by rare-earth doped sources have become a promising approach for the fabrication of all-fiber mid-infrared laser sources. This article focuses on the recent progresses of highly nonlinear chalcogenide microwires as practical gain media for far-detuned wavelength conversion towards the mid-infrared.

The combination of cellulosic materials and clays, such as Laponite, can provide composites with superior optical and mechanical properties compared to pristine cellulose. Synthetic clays can also be used as a host matrix for the immobilization of luminescent complexes, as the incorporated complexes may present enhanced emission quantum efficiency, photo and thermostability compared to the non-immobilized ones. In this way, we, herein, report the preparation of luminescent composites through the incorporation of a Eu(III) complex [Eu 3+ (tta) n ] containing Laponite (Lap) into cellulose nanofibers (CNF). The thermogravimetry results show that the obtained CNF/Lap@[Eu 3+ (tta) n ] films present higher thermal resistance than the CNF film. The Eu 3+ (tta) n species were found in the composite structure with preserved luminescence characteristics, and no leaching or degradation of the organic ligand was observed with the preparation of the composites.

Much experience in practical optical systems design (over 40 years for each author) gives us the perspective to discuss recent trends in advanced optical technologies. We give an ontology of its development and try to make a forecast for the near future, which will be useful for beginners as well as professionals in this complex field.