Anti-Stokes Cryoluminescence in Nanomaterials

Study of the electromagnetic fields interaction with structured nanomaterials with photonic band gaps is one of the most rapidly developing areas of nanophotonics. In modern optics, such nanomaterials are actively used to process the characteristics of electromagnetic radiation. Firstly, the properties of amplification of the local field are used, secondly, the properties of the photonic bandgap. A typical example of local field amplification is the work [1], in which the authors used a coating of submicron dielectric spheres on a copper target in order to achieve more than tenfold increasing the efficiency of X-ray generation. Using the properties of the photonic band gap leads to the increasing well-known nonlinear effects efficiency and to the appearance of new nonlinear phenomena. One of these phenomena is anti-Stokes cryoluminescence in nanomaterials - light emission at low temperature under laser action in the spectral range with higher frequency than that of exciting light. We observed bright and long (up to few seconds) emission in blue-green range under 20ns ruby laser pulses excitation in different nanomaterials at low temperatures [2-3]. One of the reasons of this effect is triboluminescence, free radicals appearing and structure defects forming, like in bulk materials [4]. In the present work we show that in nanomaterials of different nature there are two types of temporal dependence: short (few microseconds) and long (up to 10-12 seconds). Long dependence exists at temperatures lower than 110 K. Temporal dependence for anti-Stokes luminescence in synthetic opal matrices for temperatures lower and higher this threshold is shown in Figure 1.