New optical techniques for crystal growth from fluids

Electronic speckle interferometry (ESPI) is a non-contact optical technique commonly devoted to the observation of microscopic deformation of materials due to stress or applied loads in real time with an accuracy of the order of a wavelength of light. This interferometric technique may also be applied to the observation of physical phenomena in transparent fluids, such as density and concentration gradients during crystal growth in aqueous solution or in gel. Differently from other more common interferometric techniques, e.g. holography, ESPI can operate under ordinary room light conditions and may be arranged in a highly compact set-up. KDP crystal growth from solution has been studied with ESPI technique and data have been analysed in order to get information on solution dynamics and, furthermore, to prove the validity of this technique for crystal growth. The first results of this experience are described.