GB1173033A - Improvements in or relating to Electro-Optical Devices - Google Patents

Abstract

1,173,033. Light modulators. C. & E. BRADLEY Ltd. 11 Jan., 1968 [12 Jan., 1967], No. 1808/67. Heading H4F. A pockels cell comprises a pockets-effect body 11 having plane parallel light input and output faces 29 and 30, and two electrode asemblies 13 and 14 each comprising a chamber containing electrically conductive fluid and a loop of metal 19, 20 larger than the respective adjacent face of the crystal to which an electric potential is applied. The pockels-effect body preferably comprises a Z-cut crystal of potassium tantalum niobate, ADP or KDP, and the fluid an aqueous solution of potassium iodide or a glycerol solution of stannous chloride dihydrate. If the pockels-effect body is soluble in water two cover slips of fused quartz are bonded on faces 29 and 30. Loops 19 and 20 may be nickel square loops, the crystal 11 having the shape of a cube and being located within housing 12 of square internal and external cross-section, and silicone rubber O-rings 17 and 18, and seals 23 and 24 being positioned as shown. The fluid chambers are closed by prisms 15 and 16 of fused silica or sapphire, the outer faces 25 and 26 of which being inclined to their inner faces 27 and 28, which are parallel to the faces 29 and 30 of crystal 11, at the complement of the Brewster angle # of the material of the prism relative to air for light of a given frequency. Thus if the incident light beam 31 is plane polarized parallel to the plane of incidence and is incident upon face 25 at the Brewster angle there is no loss of light due to reflection at face 25. The embodiment shown is suitable for use with a quarterwave voltage, but if a half-wave voltage is applied prism 16 is arranged relative to prism 15 so that the plane of incidence of ray 32 at face 26 is parallel to the plane of polarization of the ray 32 on emerging from the crystal 11 when the half-wave voltage is applied, so that no reflection occurs at face 26.