Trapped charge density analysis of KTN crystal by beam path measurement

Because the function of a single crystal of potassium tantalate niobate (KTa1-xNbxO3, KTN) is largely decided by the trapped charge density inside it, it is essential to determine its value. We quantitatively estimate the charge density using two optical analysis methods, namely by investigating KTN's deflection angle when it is used as a deflector and by investigating KTN's focal length when it is used as a graded-index (GRIN) lens. A strobe technique is introduced with which to perform the measurement. The charge density values under different temperature conditions are shown. These results suggest that the charge density can be determined with both methods, and is constant in a specific temperature range. The charge density value is around 80 C/m(3) in our setup. (C) 2014 Optical Society of America