Fabrication and Properties of Thin Pb(Zr,Ti)O 3 Film Pockels Cell
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U11.3.1
Fabrication and Properties of Thin Pb(Zr,Ti)O3 Film Pockels Cell M.O. Vieitez, S.I. Khartsev, and A.M. Grishin Department of Condensed Matter Physics, Royal Institute of Technology, SE-164 40 Stockholm-Kista, SWEDEN.
ABSTRACT Longitudinal Pockels cell as a vertical ferroelectric Pb(Zr0.53Ti0.47)O3 (PZT) thin film capacitor was fabricated by pulsed laser deposition technique onto the both side polished YAlO3 + 1% Nd2O3 single crystal substrate. At first, conducting La0.5Sr0.5CoO3 (LSCO) 100 nm thick layer was deposited as an atomic template for 1 µm thick PZT film. Epitaxial quality (exceptional c-axis orientation and coherent in-plane texture) of PZT/LSCO/Nd:YAlO3 (001) heterostructure has been confirmed by x-ray diffraction. On the top, semitransparent 100 nm thick Au electrode was deposited by thermal evaporation. Intensity of the chopped 670 nm polarized laser radiation transmitted through the Au/PZT/LSCO/Nd:YAlO3 cell was measured using lock-in amplifier. Special precautions were employed to get reproducible transmittance vs. temperature scans up to 400 °C. Phenomenon of critical opalescence (scattering of the light with critical fluctuations of polarization) was observed in the vicinity of Curie temperature at 208 °C. Modulation of the transmitted light as high as 3% was achieved applying 20 V (200 kV/cm) across the capacitive cell, whereas the voltage tunability measured at 1 kHz from C-V characteristics was about 70%.
INTRODUCTION Today the optical communication is a workhorse of the data traffic. Cheap and high performance glass fibers, Er-doped optical fiber amplifiers (EDFA), and complementary semiconductor laser-photodiode pairs are the main components of lightwave communication systems. Besides these key elements, there are numerous additional functions needed to modulate, switch, combine and analyze the optical signals. The Pockels cells are devices widely used in a laser cavity to hold off lasing until a maximum population inversion has been built up in the lasing medium. Besides high speed laser shutter and pulse chopper applications they are also utilized as Q-switches, cavity dampers and polarization rotators. Basically capacitive in impedance, Pockels cells allow to minimize device RC and L/R time constants thereby owning the capability to modulate the optical phase (and hence the amplitude) on the sub-nanosecond time scale. The linear electro-optic (e-o) effect first discovered by F. Pockels in 1893 governs the function of electro-optic modulator. The refraction indices are a measure of the speed of light in a certain direction within the crystal. When an electric field is applied to a uniaxial crystal parallel to the optic axis, the refraction indices become unequal thus a phase difference in mutually orthogonal (ordinary and extraordinary) waves appears. By changing the driving voltage, the phase shift can be varied thus the dynamic retardation of the polarized light can be achieved.
U11.3.2
The most commonly used e-o materials are deuterated KD2PO4 (KDP), LiNbO3, LiTaO3 crystals a
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