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Radio frequency magnetron sputtering deposition of hetero-epitaxial strontium barium niobate thin films (SrxBa1-xNb2O6).Excellent electro-optic properties of Sr x Ba 1Ϫx Nb 2 O 6 crystals ͑SBN:x͒ motivate the attempts to control the deposition of high ordered SBN thin films with the aim of optical waveguiding and processing integration. We have examined the ability of sputtering techniques to deposit stoichiometric SBN thin films. Composition analysis has enabled us to probe the mechanisms which control the target-film composition transfer and to define an experimental strategy for stoichiometry control. Epitaxial ͑001͒ SBN thin films have been obtained on MgO ͑100͒ substrates, which exhibit two in-plane orientations ͑Ϯ31°͒ mirror symmetric to the MgO cell axis.

Implementation of the linear electro-optic ͑EO͒ effect in thin film waveguides is expected to allow drastic reductions in the drive voltage, power, and dimensions of devices devoted to light modulation. It should also enable the realization of electrically tunable photonic crystal devices. In this paper we introduce a method which eliminates systematically the sources of the unreliability which strongly affects thin film EO characterization. Based on a Fabry-Perot reflective configuration, the method enables characterizing simultaneously the EO, converse-piezoelectric, and electroabsorptive effects in a film. It provides the magnitude and sign of each of the involved coefficients, and allows accounting for the whole of experimental data versus angle of incidence for both transverse-electric and transverse-magnetic polarizations. At = 633 nm and room temperature, the results obtained with an epitaxial strontium barium niobate ͑Sr x Ba 1−x Nb 2 O 6 , x = 0.60͒ ferroelectric thin film, are: r 13 = +8.5Ϯ 1.3 pm/ V, r 33 = +38.9Ϯ 0.5 pm/ V, d 33 = ⌬e / ⌬V =+21Ϯ 4 pm/ V, and ⌬k o / ⌬V = ͑+9.8Ϯ 0.6͒ ϫ 10 −6 , where r 13 and r 33 are two linear EO coefficients, d 33 is a converse-piezoelectric coefficient, and e, k o , V represent, respectively, the film thickness, film ordinary extinction coefficient, and applied voltage. Converse-piezoelectric and electroabsorptive effects are found significant in the film response at a frequency below piezoelectric resonance. Diagonal and effective EO coefficients of the ͑Sr, Ba͒Nb 2 O 6 ͑SBN͒ film explored in the present work are larger than those of a crystal of lithium niobate ͑LN͒ at the same wavelength = 633 nm. Taking into account the significant difference in dielectric permittivity between the two materials, advances and potential of LN and SBN thin film paths are compared.

Articles you may be interested inPotential-well depth at amorphous-LaAlO3/crystalline-SrTiO3 interfaces measured by optical second harmonic generation Appl. Phys. Lett.Local crystal analysis using near-field optical second harmonic microscopy: Application to thin ferroelectric films In order to probe crystalline orientation of Sr x Ba 1−x Nb 2 O 6 ͑SBN: x͒ thin film, we have developed a detection scheme based on a scanning near-field optical microscope ͑SNOM͒. It is used to image simultaneously the fundamental and the second harmonic generation ͑SHG͒ of light by the sample under pulsed laser illumination. We demonstrate on SBN thin films that an apertureless SNOM can dramatically improve the resolution and the sensitivity of SNOM-SHG. Tip direction and focalization are the two crucial parameters in the SNOM-SHG experiments. Moreover, we show the ability of our setup to separate near field from far field contribution to the SHG. This is indeed very helpful in order to measure surface-SHG coefficients.

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In the laboratory of the Physikalisch-Technische Bundesanstalt (PTB) at the Berlin electron-storage ring BESSY II, a procedure has been developed to investigate the dependence of vacuum-ultraviolet reflection on polarization. It is based on characterizing the elliptically polarized synchrotron radiation at PTB's normal-incidence monochromator beamline for reflectometry by means of polarization-sensitive photodetectors. For this purpose, the polarization dependency in the detector responsivity was determined at a small, low, solid angle of acceptance for the synchrotron radiation, i.e., within the orbital plane of the storage ring where the degree of linear polarization is known to be almost 100%. Our method allows the polarization dependence of reflection samples to be measured with relative standard uncertainties ranging from 2.4% to 11% in the spectral range between 60 and 160 nm. The method has been applied to the optimization of polarizing mirrors at the Lyman-alpha wavelength of 121.6 nm.

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