OPTICAL FUNCTIONAI, ELEMENT USING FERROELECTRIC POLARIZATION INVERSION OF LITHIUM TANTALATE

摘要

PROBLEM TO BE SOLVED: To provide an optical functional element in which the controllability of a polarization inversion structure is improved and the resistance against optical damage is further improved. SOLUTION: The following optical elements (1) to (3) or the like can be realized by using a single crystal of lithium tantalate having nearly a stoichiometric composition with excess Li and 0.500 to 0.505 mole fraction of Li2O/(Ta2O5+Li2O) for the substrate. The elements are (1) an optical functional element which converts the wavelength of incident laser light having the wavelength in the visible to near IR region into shorter or longer wavelength by periodically reversing the polarization structure of the lithium tantalite single crystal, (2) an optical memory element or optical circuit element to record various kinds of information in the single crystal by forming polarization reversal in a minute region in the lithium tantalate single crystal in a single polarization state, and (3) an optical element which controls the laser light incident to the single crystal by using the electro-optical effect of the single crystal and which deviates, focuses or switches the light by using the large change in the refractive index in the reversal structure of the ferroelectric polarization of the lithium tantalite single crystal.