Executive Summary : | Exploration in the mid and far infrared regions are limited by the availability of materials which are responsive in these regions. Glassy samples based on chalcogenides possess broader transmission window well into the far infrared, with efficient compositional tunability based on the dopant atoms. This leads to applications in various domains like infrared optics, lasing materials, thermal sensors, energy and phase change materials etc. Most of the optical properties have been explored and exploited as devices in glasses based on sulphides and selenides, though they have a shorter window than tellurides. The ease of glass formation in them and conversion as optical devices has favoured extensive exploration of these materials. Conversely, lasing ability is limited to regions well below 4 μm even in them, which indicates the vast unexplored regions limited by material characteristics and pumping wavelengths. Telluride glasses has been mostly used for semiconducting applications, though they have longest transmission window suitable for optical applications. This has been related to formation of stable glasses and subsequent conversion as optical devices owing to their metallicity. Recent reports suggest the incorporation of tellurides in specific glass matrices improves the glass formation and associated optical properties including emission in the longer wavelength regions. This opens-up the possibility of exploring these glasses as suitable host materials for rare earth ions thereby acting as lasing sources in the mid and far-IR depending on the rare earth dopant. Efficiency of emission and the associated lasing properties have been found to be improved with precipitation of nanocrystals of rare earth ions and alkali/transition metal halides in sulphide/selenide glass matrices. This idea of nano-crystallization can be incorporated to improve efficiency in glasses synthesised based on tellurides that are also arsenic-free. Hence, synthesis of high purity telluride based glasses which can support far-infrared transmission doped with suitable rare-earth ions will be undertaken. These glasses will be co-doped with transition metals/ metal halides to obtain quantum dots/nanocrystals in glass matrix, which will improve the mechanical property for device applications. structural and thermal measurements will yield information about the network and stability of glasses, which will be utilized for tuning the compositions. Photoluminescence measurements will yield the emission wavelengths depending on the dopant ion. Optical non-linearity of these glasses will be measured using Z-scan technique with nanosecond lasers, which can also be utilized for forming optical limiting devices in these wavelength regions. Attainment of the objective will lead to lasing materials in the infrared region beyond 4 μm, which will open a new domain of applications hitherto not available with existing materials. |