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Limitations of the electro-optic response of thin potassium tantalate niobate (KTN) films caused by ferroelectric hysteresis behavior

: Gerhard-Multhaupt, R.; Yilmaz, S.; Bauer, S.; Ren, W.

Ferroelectrics 157 (1994), Nr.1-4, S.359-364
ISSN: 0015-0193
ISSN: 1563-5112
IUPAP International Meeting on Ferroelectricity (IMF) <8, 1993, Gaithersburg/MD>
Konferenzbeitrag, Zeitschriftenaufsatz
Fraunhofer HHI ()
dielectric hysteresis; electro-optical modulation; epitaxial layers; ferroelectric materials; ferroelectric thin films; pockels effect; potassium compounds; electro-optic response; ferroelectric hysteresis behavior; thin films; pulsed excimer-laser deposition; longitudinal electro-optic modulators; second electrode; epitaxial electrodes; epitaxial growth; layered samples; optical quality; eo phase shift; applications; stability; homogeneity; spatial light modulators; kta(1-x)nbxo3; ktao3nbo3

Thin films of potassium tantalate niobate (KTN) were prepared by means of pulsed excimer-laser deposition and investigated with a number of analytical techniques including electrical and electro-optical measurements. For applications in longitudinal electro-optic (EO) modulators, a second electrode is required between substrate and EO layer. Suitable epitaxial electrodes, which also permit epitaxial growth of KTN, were identified and prepared. The resulting layered samples were not only of good epitaxial and optical quality, but also exhibited maxima of the Pockels effect at the expected temperatures. It was, however, found that the linear and the quadratic EO effects became saturated at fields above 600 kV/m. The maximum EO phase shift is thus limited to roughly pi /100 for KTN films in the thickness range around 1 mu m; the saturation is caused by the ferroelectric hysteresis of KTN. Consequently, relatively thick films are necessary for most applications, which in turn requires significant improvements in the stability and homogeneity of the deposition process and limits the resolution achievable with EO spatial light modulators.