A Study Of Two-dimensional Array Optical Beam Splitter Fabricated By Periodically Poled MgLN Crystal

In1836, H.F.Talbot illuminated a periodic array grating by the plane monochromatic beam of light, self-imaging of the grating was found at specific imaging planes. This optical self-imaging phenomenon is defined as Talbot effect. Talbot effect is existed in periodic array grating devices extensively. Because of the array grating’s applicability and Talbot effect’s simplicity and delicacy, this kind of research has attracted a large number of scholars’attention.Mg-doped lithium niobate crystal (MgLN) has excellent non-linear optical properties, making it the preferable material choice of periodic array optical beam splitter devices. Therefore, we use the MgLN for a periodic two-dimensional hexagonal phase array beam splitter at first, and study its Talbot effect. By modulating the applied electric field, we can modulate the light intensity distribution of the near field diffraction. On this basis, we can study the influence of the beam splitter duty cycle D, the phase difference△φ and Talbot fraction β on the phase array beam splitter’s near-field diffraction intensity distribution. Meanwhile, with the rapid development of integrated optics, people expect more on tunable array optical beam splitter devices without applying external electric field. Therefore, on the basis of preliminary studies, we made a new Talbot array beam splitter which is fabricated by selective etching of MgLN. By changing the etching time of the array beam splitter, we can modulate the array’s phase difference△φ. This can enable the near-field diffraction intensity distribution changeable, making the device a further use in optical field. The main contents of this paper are listed as follows:1. Briefly discussed Talbot effect’s origin, development and its application.2. Introduction of the MgLN crystal’s structure and properties, and the mechanism of ferroelectric domain’s poling process were studied by applying external poling electric field.3. Theoretical research on the MgLN tunable hexagonal phase array beam splitter which based on the Talbot effect. The light intensity distribution of the near-field diffraction is obtained by numerical simulation under different conditions of the diffraction array beam splitter. On the basis of theoretical research, we design and fabricate the MgLN two-dimensional hexagonal phase array beam splitter. The experimental research verifies the results of the theoretical research.4. The Talbot effect of the two-dimensional array beam splitter which fabricated by selective etching of MgLN crystal is analyzed under different parameters. Based on the theoretical analysis, we design and fabricate different array beam splitter with different duty cycle D and different etching time. Through experimental test, the results are consistent with the theoretical analysis. Taking into consideration of the domain etching will destroy an array beam splitter’s surface structure, which is not conducive to its application in the area of precision optics, so the next step of our research will focus on further reducing the level of array beam splitter’s selective etching.