Electro-optic measurements of thin-film materials by means of reflection differential ellipsometry

Electro-optic properties of thin-film materials grown on opaque substrates are determined utilizing the principles of reflection differential ellipsometry. The scheme of the measurement involves the detection of the field-induced phase shift in a probing light beam reflected from thin-film samples. To quantitatively determine the field-induced indices change or birefringence and the field-induced strain it is essential to model the differential ellipsometric process in the stratified structure. The modeling reveals that the field-induced changes of the ordinary and the extraordinary indices contribute to the measured phase shift with different incident-angle dependences. The field-induced strain gives yet another unique incident-angle distribution. By means of an incident-angle-varying technique, therefore, the field-induced changes of ordinary index and extraordinary index in a thin-film material may be determined separately. Detailed descriptions of the measuring technique and the modeling work are presented.