Abstract
We present light induced refractive index changes in iron doped lithium niobate detected with a novel microscopy technique called ptychography. This method determines the change of the refractive index together with the intensity distribution of the writing beam from a single scan with a reconstructed spatial resolution of 3 μm and a sensitivity of the refractive index change of 10-5. We show that the light induced refractive index change is strongly connected to the intensity shape of the writing beam and that it shows the expected nonlocal behaviour. Applying the novel method to the investigation of the photorefractive effect offers an excellent opportunity to study this nonlocal response to the spatial distribution of the writing beam.
Highlights
The investigation of photorefractive materials like LiNbO3, LiTaO3, BaTiO3 or SrxBa1−xNb2O3 is of special interest for their technical application in non-linear optics like frequency mixing, wave multiplexing or holographic data storage
We present light induced refractive index changes in iron doped lithium niobate detected with a novel microscopy technique called ptychography
We have presented the application of ptychography to the investigation of light induced refractive index changes in the photorefractive material LiNbO3:Fe
Summary
The investigation of photorefractive materials like LiNbO3, LiTaO3, BaTiO3 or SrxBa1−xNb2O3 is of special interest for their technical application in non-linear optics like frequency mixing, wave multiplexing or holographic data storage. In non-centrosymetric photorefractive crystals local changes of the refractive index can be induced as a function of the intensity distribution and the lateral dimensions of an applied laser beam [1]. Processes like the photo-induced light scattering [2], the writing of holographic gratings [3] or photo-induced internal lenses [4] through the generation of macroscopic space charge fields are of fundamental interest and require the development of proper methods for their investigation. Ptychography combines the high spatial resolution of diffractive imaging with the large field of view of scanning probe techniques. In this letter we introduce ptychography for the investigation of light-induced refractive index changes in the photorefractive material iron-doped lithium niobate (LiNbO3:Fe). We determine the intensity and phase distribution of the writing beam and the lateral distribution of the refractive index change with a spatial resolution of 3 μm from a single ptychographic measurement. We propose an extension to the ptychographic algorithm and show its benefit to the spatial resolution of the reconstruction by the measurement of a test structure
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