The Research And Applications Of Polarization Coupling Effect Based On Transverse Electro-optic Effect In Periodically Poled Lithium Niobate Crystal

Light, as the basic particle, in terms of photons, has momentum, power and angularmomentum. Meanwhile, light, as a wave, has amplitude, phase, intensity, and group velocity,etc. How to realize manipulation of light is the aim of our investigation. Active control oflight, as an interdisciplinary field between nonlinear optics and information science, plays animportant part in optical communication. This paper investigated the manipulation of angularmomentum, phase and intensity, based on the polarization coupling theory.Periodically poled lithium niobate crystal is the core element of our work, and thetechnology of electrical poling of ferroelectric crystals in room temperature is reviewed.Based on the transverse electro-optic effect, two kinds of analysis methods have beenproposed, they are Jone matrix and coupling mode equations. By using these methods, wepresent two electro-optical devices for intensity modulation, they are Solc-type filter and1*2electro-optical switch. The central wavelength of this Solc-type filter could be modulated bytemperature. On the other hand, by shifting the extra electric field, the optical signal could bemodulated by the1*2electro-optical switch. What is more, under higher electric field, aflat-top spectrum can be formed, which, compared with the conventional Solc-type filter, ismore stable.During the manipulation of spin angular momentum, we found the output left-handedcircularly polarized photon, right-handed polarized photon and the total spin angular momentum could be modulated by the transverse electric field and operating wavelength.This kind of manipulation which is very flexible and effective could be used in quantum field.Based on polarization coupling theory, we propose a phenomenon of“polarization-coupling cascading” by making an analogy with second harmonic generationcascading. Polarization-coupling cascading contributes to the effective electro-optical Kerreffect that is several orders of magnitude stronger than the classical ones. Experiment ofNewton’s rings demonstrates the large phase accumulation during the polarization-couplingcascaded processes, which means the phase of light could be modulated by the transverseelectric field.Polarization-coupling cascading has a wide range of applications in optical manipulation.Based on the this polarization-coupling cascading, the parameters of light such as phase andintensity could be modulated by changing the relative power ratio of the incident continuouswave beams. The phase control was demonstrated by Newton’s rings experiment. Theseresults are of interest for researching all-optical communication in weak light field.