Tungsten trioxide (WO₃) is well-known as one of the most promising chromogenic compounds. It has a drastic change of coloration induced from different external stimuli and so its applications are developed as gas sensors, electrochromic panels or photochromic sensors. This paper focuses on the photochromic properties of nanoWO₃, with tunable composition (with tunable oxygen sub-stoichiometry). Three reference samples with yellow, blue and black colors were prepared from polyol synthesis followed by post annealing under air, none post-annealing treatment, or a post-annealing under argon atmosphere. These three samples differ in terms of crystallographic structure (cubic system versus monoclinic system), oxygen vacancy concentration, electronic band diagram with occurrence of free or trapped electrons and their photochromic behavior. Constituting one main finding, it is shown that the photochromic behavior is highly dependent on the compound’s composition/color. Rapid and important change of coloration under UV (ultraviolet) irradiation was evidenced especially on the blue compound, i.e., the photochromic coloring efficiency of this compound in terms of contrast between bleached and colored phase, as the kinetic aspect is high. The photochromism is reversible in a few hours. This hence opens a new window for the use of tungsten oxide as smart photochromic compounds.

This review focuses on the radiation-induced changes in germanate and tellurite glasses. These glasses have been of great interest due to their remarkable potential for photonics, in terms of extended transmission window in the mid-infrared, ability of rare-earth loading suitable with a laser, and amplification in the near- and mid-infrared or high nonlinear optical properties. Here, we summarize information about possible radiation-induced defects, mechanisms of their formation, and the influence of the glass composition on this process. Special attention is paid to laser-induced structural modification of these glasses, including possible mechanisms of the laser-glass interaction, laser-induced crystallization, and waveguide writing. It is shown that these methods can be used for photostructuring of the glass and have great potential for practical applications.

The ability to produce robust fiber-based integrated optical systems operating over a wide spectral domain (UV to mid-infrared), is one of today’s key challenges in photonics. This work reports on the production of crystal-free, light guiding fibers from rich Ga₂O₃ oxide-based glass compositions. These materials show optical transmission extending from ultraviolet wavelengths (∼0.280 µm) up to 6 µm in the IR for millimeter length scale while exhibiting relatively high vitreous transition temperatures (∼735 °C), nonlinear optical properties and improved surface micro-hardness. This combination of superior thermal, mechanical and optical properties represents a promising alternative for the development of robust fibers operating in the visible up to the 3–5 µm window.

Structure, linear and nonlinear optical properties of glasses in the ternary system (90-x)GeO2-10Na2O-xTa2O5 have been investigated. These glasses exhibit a wide transparency window from 350nm to 5500nm and refractive index ranging from 1.78 to 1.93. Upon a thermal poling treatment under nitrogen atmosphere using increasing poling voltages, SHG quantitative measurements were performed and have confirmed the electro-optical origin of the second order optical responses, (2) values ranging from 0.06pm/V to 0.3pm/V were obtained depending on the poling conditions and glass composition. SHG/Raman correlated microscopy measurements allowed to identify the structural changes within the poled layer and pointed out that sodium depletion lead to a more connected glass network through cross-linking bonds such as Ge-O-Ge and Ta-O-Ta bonds. A deviation from a pure electro-optical second order response is observed for the highest poling voltage. In this particular case, a linear optical birefringence and a structural (2) might have to be taken in account to describe accurately the polarized layer optical properties.