Post-melting encapsulation of glass microwires for multipath light waveguiding within phosphate glasses

Glass waveguides remain the fundamental component of advanced photonic circuits and with a significant role in other applications such as quantum information processing, light generation, imaging, data storage, and sensing platforms. Up to date, the fabrication of glass waveguides relies mainly on demanding chemical processes or on the employment of expensive ultrafast laser equipment. In this work, we demonstrate the feasibility of a simple, low-temperature, post-melting encapsulation procedure for the development of advanced glass waveguides. Namely, silver iodide phosphate glass microwires (MWs) are drawn from typical splat-quenched samples. Following this, the MWs are incorporated in a controlled manner within previously prepared transparent silver phosphate glass rectangular prisms. The composition of the employed glasses is chosen so that the host phosphate glass has a lower refractive index than the embedded MWs. In such case, the waveguide mechanism relies on the propagation of light inside the encapsulated higher refractive index MWs. Moreover, the presence of silver nanoparticles within the MWs enhances the light transmission due to scattering effects. Waveguide devices with either one or two incorporated MWs were fabricated. Remarkably, in the latter case, the transmission of light of different colors and in multipath direction is possible, rendering the developed waveguides outstanding candidates for various photonic circuits, optoelectronic, and smart sign glass applications

Space weathering simulations through controlled growth of iron nanoparticles on olivine

Airless planetary bodies are directly exposed to space weathering. The main spectral effects of space weathering are darkening, reduction in intensity of silicate mineral absorption bands, and an increase in the spectral slope towards longer wavelengths (reddening). Production of nanophase metallic iron (npFe0) during space weathering plays major role in these spectral changes. A laboratory procedure for the controlled production of npFe0 in silicate mineral powders has been developed. The method is based on a two-step thermal treatment of low-iron olivine, first in ambient air and then in hydrogen atmosphere. Through this process, a series of olivine powder samples was prepared with varying amounts of npFe0 in the 7-20 nm size range. A logarithmic trend is observed between amount of npFe0 and darkening, reduction of 1 µm olivine absorption band, reddening, and 1 µm band width. Olivine with a population of physically larger npFe0 particles follows spectral trends similar to other samples, except for the reddening trend. This is interpreted as the larger, ~40-50 nm sized, npFe0 particles do not contribute to the spectral slope change as efficiently as the smaller npFe0 fraction. A linear trend is observed between the amount of npFe0 and 1 µm band center position, most likely caused by Fe2+ disassociation from olivine structure into npFe0 particles.Peer reviewe