Simultaneous characterization of the electro-optic, converse-piezoelectric, and electroabsorptive effects in epitaxial (Sr,Ba)Nb2O6 thin films

Abstract

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.

Lattice guiding for sputter deposition of single domain (Sr0.6Ba0.4)Nb2O6ferroelectric thin films

“…This refractive index is in agreement with 2.30 at 55 633 nm obtained for highly oriented SBN60 thin films on platinised MgO substrates. 11 The film thickness extracted from the prism coupling measurements was 1.02 μm, which matches the expected value of ~1.05 μm. Piezoresponse force microscopy (PFM) is increasingly used to 10 characterise the ferroelectric properties of thin films, and, in particular, to study the distribution and polarity of domains.…”

Local polarization in strontium barium niobate (SBN) epitaxial thin films investigated using Kelvin Force Microscopy (KFM)

“…The non linear properties of the SBN epitaxial thin films we prepare compete with those of (Ba, Sr)TiO 3 thin films for dielectric tunability and with those of LiNbO 3 crystals for electro-optic properties [1,2]. However the polarization, piezoelectric and electro-optic coefficients of SBN films are obtained lower, by a common factor about 5, than those of SBN crystals.…”

Effect of LiSbO3 on the phase structure, microstructure and electric properties of Sr0.53Ba0.47Nb2O6 ceramics

“…Strontium barium niobate Sr x Ba 1−x Nb 2 O 6 (SBN) is a ferroelectric solid solution between BaNb 2 O 6 (BN) and SrNb 2 O 6 (SN) which has a tungsten bronze (TB) structure with a unit-cell formula of [(A1) 2 (A2) 4 C 4 ][(B1) 2 (B2) 8 ] 30 . In the formula, A1, A2, B and C sites are 15-, 12-, 6-and 9-fold coordinated oxygen octahedral sites in the crystal lattice structure, respectively, where the A1 and A2 sites can be occupied by Sr 2+ , Ba 2+ , Ca 2+ , Pb 2+ , K + , Na + and some rare earth cations, the B sites by either Nb 5+ or Ta 5+ , the C sites by Li + and other small cations.…”

“…This allows us to adjust the Sr/Ba ratio to suit the different needs with appropriate physical and dielectric properties [2][3][4]. SBN is important in many technological applications such as electro-optic, pyroelectric, piezoelectric and photorefractive device because of its excellent pyroelectric and linear electro-optic coefficients [5][6][7][8].…”