Characterization and generation of white light in rare earth ions doped zinc oxide telluride (TeO2-ZnO) glasses

Today, multicolor visualization and optical devices and their progression convey a great importance, owing to the mass usage of vision display devices and the widespread indoor utilization of three dimensional (3D) displays. Apart from personal utilization, techniques and devices of visualisation and vision display appear to be practical also in the field of bio-medical applications. A large scale of devices used for visualization, aim to broadcast quality that the vision will flow in the original data quality without creating any obstacles in the eye at visible light spectrum (VIS), which can be perceived by human eye. Transfering total visible spectrum comprising the medium tones of color and liveliness, together with technical backgound to procure the least pause in the flow of vision, there appears the need for the white light (WL). Numerous investigations are carried out to meet the deficiency. Recent studies are conducted also by upconversion (UC) method, with mixing tellurite glasses, fluorid glasses, ceramics and rare earth (RE) elements. It is accentuated in the literature that amongst advantages of the techniques of white light UC there can be pronounced a much more sensitive attaining of the perceived and transmitted color, its high resolution, stability, visualisation interval, volume of tehnique treated in devices, duration of cheaper production. The objective of our study is to contribute to the meeting of the required progress and industrial requirements. Emission characteristics of RE ions (REI's) for display technology and other solid state illuminations are wavelength, spectral line width, and line intensity respectively. Spectral width of emission for REI's originate by the gliding of free ion levels due to the presence of the effectiveness by braid phonons. Whereas there is some weak effectiveness between the REI's and the braid, gliding of these levels are insignificant, which realizes a favourable benefit in display applicatons. Line strength depends upon the nature of special transitions and hosting materials, due to rare-earth ions. The probability for a given emission is the function of the strength of local electric dipole depending upon the index of refraction on REI's and line strength. Whereas the radiative lifetime or quantum efficiency is a function of emission probability, materials with higher refractive index present higher quantum efficiency. Colors and wavelengths of lights that can be seen with bare eyes in visible spectrum can be measured at room temperature as blue (476 nm), green (530 and 545 nm), and red (656 nm). There are filtering methods to obtain all visible colors in visualisation devices (display units). The basic values defined for color by the photometer are known as tristimulus values namely HUE, saturation, brightness (luminence) (HSB/ HSL). Their reciprocals in physical optics are dominant wavelength (HUE), intensity of light (intensity/ saturation) and value of illuminance (luminance/ brightness). CIE 1931 RGB which is known as the international color standard accepts the values of tristimulus values as basis, which is the standard color characterization. The study of Tm3+, Er3+, and Yb3+ doped zinc tellurite glasses (TeO2-ZnO) aims the emission at the frequencies of red, green and blue under laser excitation 805 nm and 980 nm via UC mechanism and the relative productivity of luminescence output. Transformation mechanism of up-conversion depends upon the effectivity between rare earth ions. For the white light upconversion, due to the applicatons in optics, photonics and electronics, as can be noticed by the examinaton of literature, numerous experimental techniques have been used in the recent years. For solid color visualisation devices, the multicolor display technique is under progression as a new technique. Altough up-conversion process allows the making of white light laser, the background illumination in three dimensional displaying devices are utilized in white light source and for developing systems that can be used in displaying/ visualisation devices. They also have great importance in the development of white light laser and LED. There are additional numerous areas of applicaton. Further, the study comprises upper energy transformation processes in tellurium zinc oxide glass materials mixed with rare earth elements and the examination of optic parameters effecting the production of WL. Lifetime of the optical materials whose synthesis have been materialized by meltquenching method have been examined, with regards to REI's concentration. Optical specifications of zinc oxide-tellur dioxide host materials doped with Er3+ , Tm3+ , and Yb3+ have been examined by using two optical methods regarding to the ratio of luminescence intensity and measurement of lifetime of the transition levels. The procured color coordinates (x-y-z) will be compared with the white point datum identified in international color standard diagram (CIE x-y 1931 chromaticity diagram). The present study has been conducted at the Laser Material Research Laboratory in ITU (Istanbul Technical University) Physics Department. Subject of the research comprises whether TeO2 -ZnO composite materials doped with Er3+, Tm3+, and Yb3+ ions by excitation at NIR-IR-VIS intervals via up-conversion mechanism can be utilized at the UC of white lights, using luminescence intensity, line position and lifetime techniques. The synthesis of TeO2 -ZnO composite glass materials doped and co-doped with Er3+/ Tm3+/ Yb3+ at various combinations have been compared with white light region (white point/white region) in color coordinates chromaticity diagram, prepared according to CIE 1931 x-y standards, using laser spectroscopy techniques utilizing luminescence, dominant wavelength and light intensity specifications of the materials. Luminescence spectroscopy is used in the measurement of lifetime of electronic transitions and width of luminescence transition lines that optically occur in solids doped with active ions and their positions,. The effect of the annealing heat on position of luminescence transition lines, width of band duration of life, and intensity of illumination be examined. The study will definitely help to the research and progression activities in the field of three dimensional visualisaton, which are known to be the latest techniques of WL up-conversion solid color display devices considerably required in industrial applications of photonic and optical devices. In accordance with the aim of our study, it has been examined whether zinc oxidetellur dioxide composite glasses can be used for the production of white light base on upper energy transition mechanism, by excitation of 805.2 and 980 nm laser light, following the mixture with Er3+, Tm3+, Yb3+ ions at the suggested proportions. Thus it has been aimed to directly contribute to the realizaton of the project and production of photonic devices comprising WL usage. Moreover, in addition to the luminescence spectrum data obtained by the stimulation of 805.2 and 980 nm laser with UC mechanism, by stimulating the patterns with 980 nm laser and diversing the source of the current via operating the UC mechanism, quantity of the photons (n) has been procured by curve analysis of luminescence spectrum graphics of cast iron due to varying power. Thus, the required data has been procured for sketching the scheme displaying the energy transfer amongst lanthanide ions. The same has been published. The study finally displays by tables at the conclusion chapter the CCT, CRI, CIE x-y values of rare earth ion doped glass patterns that are measured by UC mechanism under 805.2 nm and 980 nm laser beam. As a result, these values have been interpreted by comparing the color coordinates (x-y) and white point/white region data quoted in CIE 1931 x-y International Choromaticity diagram.