Frequency up-conversion is a technique for the generation of high energy photon from two or more lower energy photons. Although many up-conversion techniques have been demonstrated such as parametric up-conversion or multi-photon absorption, their conversion efficiencies become negligible for high-order up-conversion. Alternatively, in thermal emission very high temperatures are needed for reasonable efficiencies and the emission is spectrally broad rendering this up-conversion method impractical for most applications. We present a new efficient extreme up-conversion method for generating NIR and visible wavelengths using CW LWIR laser by non-thermal-equilibrium excitation through spontaneous reduction of the chemical potential. In this method we exploit the high chemical potential of the pump specific modes to excite the vibronic states of the host, subsequently transferring the energy to chosen emitters, resulting in narrow non-thermal steady-state emission. All while, only residual energy contributes to material's temperature, thus keeping it at a comparably low temperature. We experimentally demonstrate 7, 10, 13, 16, and 20-fold up-conversion at external efficiency of up to 4%, exceeding black-body radiation of the bulk temperature. Furthermore, we present energy transfer between emitters, a phenomenon in contrast to thermal emission, showing the photoluminescence behavior of this method. We use CW CO2 laser (10.6m) to excite silica vibronic states and transfer the energy to rare-earth emitters at the NIR and visible spectrum. This new outlook on up-conversion via energy transfer paves the way for developing new light sources and new methods of imaging and detection with high efficiencies.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon