Effect of axial misalignment and multiple reflection on jones matrix of a four‐crystal light modulator

Abstract

AbstractThe latest off‐the‐shelf 45 X‐cut (ADP or KDP) four‐crystal light modulators with low driving voltage consist of four crystal units to accomplish temperature compensation and to make possible a low driving voltage. Therefore, axial misalignment is not uncommon. Also, because there are many interfaces between the crystals and the matching dielectric fluid, multiple reflection may cause problems. the effects of these phenomena on the Jones matrix describing the fundamental characteristics of optical phase modulation are examined. First, the dielectric tensor of the crystals with axial misalignment and the characteristic plarizations in the crystal are derived. Then, using Berreman's 4 × 4 matrix formulation, the Jones matrix representation of a four‐crystal light modulator with axial misalignment is derived. It is pointed out that the off‐diagonal terms arise from axial misalignment, which is one cause of temperature variation of the light modulator characteristics. A numerical estimate is made of the effect of multiple reflection. It is pointed out that the effect of multiple reflection on the off‐diagonal elements of the Jones matrix is negligible while the effect of the diagonal elements is substantial. an experimental example with an actual modulator is given to determine the location of the axial misalignment.