A Study Of Tunable Array Beam Splitter Fabricated By Domain Etching In MgLN Crystal

The Talbot effect is a self-imaging phenomenon of near-field diffraction, first observed in 1836 by Henry Fox Talbot. H.F.Talbot illuminated a periodic array grating by the plane monochromatic beam of light, self-image of the grating was found at regular distances away from the grating plane. This optical self-imaging phenomenon is defined as Talbot effect. Talbot array illuminator is a device that splits singular light beam into an array of beams with periodical optical intensity based on Talbot effect. It has been widely used in optical computing, multiple imaging and optical metrology. This kind of research has attracted a large number of scholars’attention.LiNbO3 (LN) crystal is a kind of practicable material for Talbot array illuminator due to its perfect optical characteristics. However, The photorefractive effect and green or blue induced infrared absorption limited the performance of the Talbot array illuminator using PPLN. MgO-doped LiNbO3 (MgLN) crystal showed shorter absorption edge wavelength and higher resistance to photorefractive damage than that ofLN.So we fabricated a Talbot array illuminator based on PPMgLN at first. By modulating the applied electric field, we can modulate the light intensity distribution of the near field diffraction. Then we can analyzed the effects of the array illuminator’s duty cycle D, the phase difference △φ and Talbot fraction β on the array illuminator’s near-field diffraction intensity distribution.The conventional method to fabricate a Talbot array illuminator is using high external electric field to modulate the phase difference. However, essential high external electric field restricts the Talbot array illuminator to applying in optical integration and optical micro structure devices. Now we are looking forward to a new way which avoids using high external electric field. Therefore we fabricated a Talbot array illuminator through spatially selective etching MgO-doped LiNbO3 by HF to modulate the phase difference. This can enable the near-field diffraction intensity distribution changeable, which is good to be used in optical integration economically and conveniently. The main contents of this paper are listed as follows:1. Introduction of the Talbot effect’s origin, development and application.2. Briefly discussed 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. The light intensity distribution of the near-field diffraction is obtained by numerical simulation under different conditions of the diffraction array illuminator. We design and fabricate the MgLN array illuminator by using high external electric field. The experimental research verifies the results of the theoretical research.4. The domain-etching Talbot array illuminator was fabricated through spatially selective etching MgO-doped LiNbO3 by HF. For the first time, we experimentally and theoretically analyzed the effects of array duty cycle and domain-etching depth of Talbot array illuminator based on PPMgLN crystal. Optimal parameters of simulation were obtained according to the intensity distribution of array spots in diffraction field.