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1Window functions applied in laser interferometry to investigate the spatial inhomogeneities and characteristics of waveguide elements optically induced in a lithium niobate crystal
A.D. Bezpaly1*, A.A. Novoselov1, A.E. Mandel1, V.I. Bykov1
1- Tomsk State University of Control Systems and Radioelectronics, Tomsk, 634055 Russia
The laser radiation influence on various materials has been studied since the last century and has found application in such fields of science and technology as laser technologies, nonlinear and integrated optics, holography, optoelectronics, and photonics. Laser radiation may also be useful to create optical waveguide and diffraction elements or modify their characteristics in integrated photonic circuits and other compact quantum devices. The widely used material for such devices is lithium niobate crystal because of its unique set of optical, acousto-, and electrooptical properties. It is also known that the introduction of various impurities into the lithium niobate crystal can change its properties, including its sensitivity to optical radiation in a certain range. Using light influence on the lithium niobate, it is possible to induce different inhomogeneities both in the near-surface and bulk areas of the substrate. However, to create integrated optical devices based on waveguide and diffraction elements by inducing inhomogeneities, information about modulated refractive index in the local area is required. The value and spatial distribution of refractive index changes in the local area may be investigated by laser interferometry. This method is useful to study both large and small inhomogeneities with various topologies, but it has some difficulties when processing interferograms. To solve this problem, we propose in our work to use window functions when processing interferograms obtained in areas with optically induced refractive index changes. Our results show that using the window function makes interferogram processing simpler. It may also be useful for different areas of science and technology using the two-dimensional Fourier transform.
