Thermographic evaluation of Er-doped silica fiber as IR-to-visible image converter

Abstract

A novel concept for IR-to-visible converter is based on the up-conversion, upon pumping with the near IR radiation. The theoretical heat transfer predictions were followed by the experimental results whereby the fiber was maintained at a series of temperatures. Currently, an IR camera (2003 CEDIP), sensitive in the spectral range from 8 μm to 12 μm is being used to ascertain the validity of the temperature measurements. 1. Upconversion-based IR-to-visible converter Recently, temperature sensor concept has been described that is based on the upconversion process in the Er-doped silica fiber. When the material is irradiated with the near IR radiation of about 800 nm, the visible radiation in the spectral interval 400 nm to 500 nm is generated, with the spectral distribution depending only on the sample temperature.[1,2] This process may be described as the conversion of spatial temperature distribution to the spatial distribution of visible radiation – a visible image.[3] For feasibility assessment, we are using an optical fiber. The first step is to quantify its capacity to generate, maintain, and refresh the thermal image in space and time. For the spatial resolution determination, two hot spots are imaged on a piece of the Er-doped silica in a form of a fiber. The fiber photograph is shown in Figure 1: part (a) is in the visible and (b) is in the IR, also illustrating temperature distribution. An important feature of a dynamic IR image converter is its ability to conserve and erase the thermal image, once it has been imprinted on its surface. Temperature distributions are generated with several types of irradiation sources. Fig. 1b. Fiber observed in IR, with core temperature distribution from 28.70 C to 28.77 C. (White is cooler.) http://dx.doi.org/10.21611/qirt.2004.083