In honor of the International Year of Glass 2022 (IYoG'22), this article highlights important aspects of glass and light, focusing on more advanced photonic applications that drive a great many current and future commercially and societally beneficial products and services. Topics include a brief history of photonic glasses, an overview of light guiding, the subsequent use in planar waveguide devices, and their ubiquity as carriers of information and sensors in the form of optical fibers. These sections highlight the strong interconnections on the understanding of the glass composition, glass structure and optical properties. For next developments in glass photonics, new opportunities will be offered by machine learning, artificial intelligence, 3D printing and additive manufacturing. Additionally, the future of glass photonics may also depend on our ability to meet current challenges such as climate change, i.e., the development of an environmentally-friendly manufacturing process, considering environmental impact and possible material shortages.

Planar polycrystalline laser waveguides with the structure YAG/Yb:YAG/YAG were produced by ceramic processing. Transparent ceramics represent a valid alternative to single crystals as the flexibility of the ceramic process paves the way to new application opportunities. The implementation of different ceramic shaping techniques allows the production of complex or multicomponent (composite) structures that are generally difficult or about impossible to obtain with single crystals. A practical example are the planar structures presented here, characterized by a strict control of the dopant distribution obtained already during the shaping process, without further machining or bonding. The waveguides are composed of a laser active Yb:YAG layer obtained by tape casting with a thickness between 100 and 250 ?m placed between dopant-free YAG cladding obtained by oxide powder mixing. The refractive index of Yb:YAG is higher than YAG thus realizing a multimode waveguide. Two types of geometries were tested: 1. simple planar waveguide with a sandwich structure (confinement in one direction); 2. waveguide with a rectangular cross section (confinement in two directions). The waveguides were tested for laser emission in a cavity end pumped by a fiber coupled diode laser, under quasi-CW pumping conditions (rectangular pump pulses with 10 ms duration, 10 Hz), delivering up to 60W at 936 nm. The planar waveguide has shown a maximum output power of 14.4 W (slope efficiency 39.1%, optical efficiency 27.4%) whereas the 2D waveguide had a maximum output power of 11.6 W (slope efficiency 38.4%, optical efficiency 22.4%). Lasing wavelength was 1030 nm.

Active and passive optical waveguides are fundamental elements in modern telecommunications systems. A great number of optical crystals and glasses were identified and are used as good optoelectronic materials. However, fabrication of waveguides in some of those materials remains still a challenging task due to their susceptibility to mechanical or chemical damages during processing. Ion beam has been used for such purposes, along with other emerging techniques, like direct pulsed laser writing. Passive and active planar and channel optical waveguides, and optical Bragg gratings were fabricated in various glasses (like Er: TeO2-WO3 glass) and undoped and doped crystals, Bi4Ge3O12, Bi12GeO20) using masked or unmasked macrobeams or microbeams of light and medium-sized ions (C, N, O) in the 1.5 - 11 MeV energy range. Functionality of the optical elements was tested by m-line spectroscopy and end fire coupling technique. Structural changes in the implanted samples were studied by various optical microscopic techniques, spectroscopic ellipsometry, Rutherford backscattering and microscopic Raman spectroscopy. The results show that it is possible to produce integrated optical elements of unique properties using ion beam techniques

Glass-ceramics are a kind of two-phase materials constituted by nanocrystals embedded in a glass matrix and the respective volume fractions of crystalline and amorphous phase determine the properties of the glass-ceramics. Among these properties transparency is crucial in particular when confined structures, such as, dielectric optical waveguides, are considered. Moreover, the segregation of dopant rare-earth ions, like erbium, in low phonon energy crystalline medium makes these structures more promising in the development of waveguide amplifiers. Here we are proposing a new class of low phonon energy tin oxide semiconductor medium doped silicate based planar waveguides. Er3+ doped (100-x) SiO2- xSnO2 (x= 10, 20, 25 and 30mol%), glass-ceramic planar waveguide thin films were fabricated by a simple sol-gel processing and dip coating technique. XRD and HRTEM studies indicates the glass-ceramic phase of the film and the dispersion of ~4nm diameter of tin oxide nanocrystals in the amorphous phase of silica. The spectroscopic assessment indicates the distribution of the dopant erbium ions in the crystalline medium of tin oxide. The observed low losses, 0.5±0.2 dB/cm, at 1.54 ?m communication wavelength makes them a quite promising material for the development of high gain integrated optical amplifiers.

We report on the fabrication and characterization of planar waveguides in an Er-doped tungsten-tellurite glass by implantation of 3.5 MeV N + ions. Implantations were carried out in a wide fluence range of 1 · 10 16 8 · 10 16 ions/cm 2. Waveguides were characterized by m-line spectroscopy and spectroscopic ellipsometry. Irradiation-induced refractive index modulation saturated around a fluence of 8 · 10 16 ions/cm 2. Waveguides operating at 1550 nm were obtained in that material using 3.5 MeV N + ion implantation.

A numerical model for Yb3+ sensitized Er3+-doped silica-titania channel waveguide amplifiers is developed and implemented in a computer code. The possibility of achieving high gain with a reduced length is demonstrated and for a copropagating pump power of 100 mW, a gain G= 6.2 dB is calculated a with a noise figure F=4.22 dB.

A numerical model for Yb3+ sensitized Er3+-doped silica-titania channel waveguide amplifiers is developed and implemented in a computer code. The possibility of achieving high gain with a reduced length is demonstrated and for a copropagating pump power of 100 mW, a gain G= 6.2 dB is calculated a with a noise figure F=4.22 dB.

In this paper, we report the first successful demonstration, to our knowledge, of two-photon fluorescence excitation (TPFE) using planar thin-film waveguide structures of macroscopic excitation dimensions (square millimeters to square centimeters in size). The high intensity of excitation light required for TPFE is available not only at a single focus point but along the whole trace of the beam guided in the waveguide structure. Line profiles of the fluorescence excited by TPFE show excellent correlation with the geometry of the launched laser beams. A clear second-order dependence of the fluorescence intensity on the excitation intensity confirms the two-photon character of fluorescence generation. Spectra of the emission generated by one-photon excitation and by two-photon excitation show only minor differences. (C) 2003 Elsevier Science B.V. All rights reserved.

A planar waveguide dye laser, driven by commercial xenon flashlamps with an average power output of 200 W at 50 pulse per second (pps) is described. Due to the planar structure, a narrow bandwidth operation down to 10 GHz has been obtained with a single grating arranged at grazing incidence. With this configuration, high overall efficiency up to 0.6 percent has been obtained, partially due to energy conversion of the broad-band emission spectrum of the flash-lamps by circulating an appropriate dye solution between flashlamps and reflectors.