Theory of a 2×2 switch based on electro-optic and piezoelectric effects in photorefractive LiNbO 3 crystal

Abstract

ABSTRACT Based on the electro-optic and piezoelectric effects, principle of a 2™ 2 bypass-exchange switch in photorefractive LiNbO 3 crystal is discussed. In photorefractive volume grating, the Bragg condition can be deviated by applying a specific field during readout. That is, by applying a specific field E s or zero field, the diffraction efficiency will be 0 or 1, and this property can be used to realize the exchange or bypass operation of the switch. In this paper, on considering both the piezoelectric and the electro-optic effects caused by the applied electric field, we analyzed relations of both the specific field and the incident intensity ratio with respect to the writing angles and polarizations of writing beams. Keywords : bypass-exchange switch, electro-optic effect, piezoel ectric effect, diffraction efficiency, Bragg condition 1e INTRODUCTION Comparing to the mechanical switch, the optical switch has the properties of broadband, high signal to noise ratio (SNR), rapid switching time, and the ability to provide noncrosstalk and high density interconnect. Among the fabrication schemes of optical switches, those based on photorefractive hologram are most attractive. The reason is that the photorefractive material has high diffraction efficiency, rapid responding time and reconfigurable property. Based on photorefractive effect, many fabricating schemes have been proposed[1-5]. In a former paper[6], we have proposed an electric-field controlled 2™ 2 bypass-exchange switch. In that paper, we consider only the electro-optic effect when applying a field, but did not consider the piezoelectric effect. It is valid in some conditions (see discussion in section 4), but for others, it is not. In this paper, we will consider both the electro-optic and piezoelectric eff ects to realize the same switch. This paper has four sections. Introduction is section 1; Section 2 will introduce the theory of the switch; Section 3 discusses the piezoelectric and electro-optic effects of photorefractive crystal when applying a field to the crystal; In section 4 we will compare the Bragg angle deviation caus ed by piezoelectric effect and electro-optic effect.