Electro-optic Tunable Talbot Effect Based On Periodically Poled LiNbO3Crystals

Diffraction optics is the theory that is widely used in the design ofoptical elements and which has many excellent peculiarities. Optical ArrayIlluminator is an element which is formed based on diffraction optics. It isused for splitting a laser beam into many or some special patterns withperiodical array. This kind of illuminator element which is based ondiffraction optics characterizes smaller volume and higher efficiency. TheOptical Array Illuminator is now widely used in photoetching, laser arrayilluminator, and polarization-resolving optics and so on.In this paper, we chose a kind of optical-super lattice structure,periodically poled LiNbO3crystal (PPLN), which has a large electro-opticcoefficient. The ferroelectric domain of PPLN is reversed periodically, whenan external electric field is applied on the z axis of this PPLN, the threeprincipal refractive indexes will change, benefitting from the modulation ofelectro-optic coefficient and the reversal of the ferroelectric, the phasechanges periodically on the output surface, a phase grating is formed.Every grating has Talbot effect, this kind of optical-super latticestructure phase grating would get lots of patterns of intensity distribution indifferent Talbot distance or different external electric field, and could be tuneartificially, a diffraction optical array illuminator is formed. In this paper, weused this illuminator to record patterns of intensity distribution in thesimulation and in the experiment under different conditions. Theexperiments were good agree with theory.Compared with other optical illuminator, our illuminator which is by the optical-super lattice structure has a small volume and a light weight,which make the elements easy integration. And the phase type grating couldmake the efficiency up to100%in theory and get a higher resolution thanamplitude grating illuminator. Meanwhile, the phase of PPLN could be tuneby external electric field, in this way, the diffraction intensity distributioncould be precisely modulated. Compared with other array illuminators, thistunable illuminator uses a lower voltage and could get a more concentratedintensity distribution. At the same time, the influence of the incident angle tothe self-imaging patterns was studied for the first time, four interestingpatterns, the period of intensity distribution reduced by half and the chirpdistribution appeared, under two angles was recorded,This flexibly tunable Talbot self-imaging could display varied intensitydistribution patterns and may make Talbot effect more useful in opticaltechnologies.