Growth of nonlinear optical thin films of KTa1−xNbxO3 on GaAs by pulsed laser deposition for integrated optics

Abstract

We report successful deposition of epitaxial nonlinear KTa0.52Nb0.48O3 (KTN) films on (100) GaAs substrates. A buffer layer scheme consisting of epitaxial MgO and SrTiO3 buffer layers and a Si3Ni4 encapsulation of the substrate was developed to alleviate chemical and structural incompatibilities between the GaAs substrate and KTN film at the growth temperature (∼750 °C). The structure, composition, and preliminary optical properties of the KTN films were evaluated by four-circle x-ray diffraction, Rutherford backscattering spectrometry, and prism coupled optical waveguide mode measurements, respectively. We observed sharp and distinguishable transverse electric and transverse magnetic propagating modes in the KTN films, and measured the refractive index (n0) of the film at 488 nm to be 2.275 which is close to the bulk value of 2.35, all of which indicates a high structural and optical film quality.

Epitaxially grown ferroelectric thin films for agile devices

“…Various methods were also carried out for KTN thin films deposition, like liquid-phase epitaxy [85], MOCVD [86,87], sol-gel methods [51][52][53]88] (including polymeric precursors [54,55]), radio frequency sputtering [56,89] and PLD [39,40,46,[90][91][92][93][94][95]. Most of these studies highlighted the difficulty to preserve the relationship between metal atoms according to the pseudo-binary diagram established for the synthesis of KTN single-crystals [45,85,96] or ceramics [16,44,97].…”

“…The adjustment of the Curie temperature to a value close to the temperature of experiment would lead to high values of permittivity (maximum when T À T c ) and broad effects into electro-optical and nonlinear optics [46][47][48]. KTN is also an attractive material for applications in various fields like the storage of holographic data, parametric oscillators, pyroelectric detectors, and generators of second harmonic thanks also to reasonable dielectric losses, strong values of polarization to saturation, and low values of the electric field required to modify the properties of material [16,39,49,50].…”

“…We chose to use enriched single targets consisting of closely mixed KNbO 3 , KTaO 3 and KNO 3 powders [95]. Alternative approaches are the use of segmented targets containing KTN (or components KNbO 3 and KTaO 3 ) and KNO 3 [46,92,93,99] or standard stoichiometric targets, but with a subsequent annealing of the films under K 2 O/O 2 [91] or inside a closed KTN ceramic vessel [39], in order to compensate the potassium deficiency. The final stoichiometry of films is obviously sensitive to the excess amount of potassium in the target, the oxygen pressure, the substrate temperature and the target-substrate distance.…”

Control of potassium tantalate niobate thin film crystal phase and orientation by atomic layer deposition

“…Incorporating KTN with its strong EO properties uniformly over large areas during the fabrication of integrated photonics would greatly enhance modulator performance; a key component of all photonic systems. Because of its great potential, many growth methods have been investigated to deposit KTN: bulk growth, 3,[9][10][11] solgel, [12][13][14][15][16][17] pulsed laser deposition (PLD), [18][19][20][21][22][23][24][25] and metalorganic chemical vapor deposition (MOCVD). 26 The bulk growth process is slow and produces boules only about 4 cm wide.…”

Control of composition and structure of ferroelectric oxide thin films grown by pulsed laser deposition

“…KNO 3 [21,22] or KNbO 3 , KTaO 3 and KNO 3 [23,24], respectively. Another reported method consists in carrying out the deposition of thin films by PLD from stoichiometric targets and subsequently annealing them under K 2 O/O 2 in order to compensate the potassium deficit in the thin film [25].…”