Direct-Write E-beam Submicron Domain Engineering in LiNbO 3 Thin Films Grown by Liquid Phase Epitaxy
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Direct-Write E-beam Submicron Domain Engineering in LiNbO3 Thin Films Grown by Liquid Phase Epitaxy Ji-Won Son1, Yin Yuen1, Sergei S. Orlov1, Bill Phillips1, Ludwig Galambos1, Vladimir Ya. Shur2, and Lambertus Hesselink1 1 Solid State Photonics Lab, Stanford University, Stanford, CA 94305, U.S.A. 2 Institute of Physics and Applied Mathematics, Ural State University, Ekaterinburg 620083, Russia
ABSTRACT We demonstrate submicron ferroelectric domain engineering in liquid phase epitaxy (LPE) LiNbO3 thin films grown on LiNbO3 and LiTaO3 substrates using a direct-write electron beam poling for waveguide applications. LiNbO3 thin films of several-micron thickness were grown using a flux melt of 20 mol% LiNbO3-80 mol% LiVO3. To engineer domain structures in Z- oriented LPE LiNbO3 films, a direct-write electron beam poling was implemented. It is shown that we can engineer the domain structure of LPE LiNbO3 films by using direct e-beam poling, even though the domain orientations of the film and the substrate are opposite. We also compared e-beam poling behavior in a congruent LiNbO3 single crystal and a LPE LiNbO3 film. Using the same e-beam scan parameters, a much enhanced domain structure is obtained in LPE films. Defect structure and composition effects are also discussed. INTRODUCTION Domain engineering in LiNbO3 has been studied intensively for various applications such as quasi-phase matched optical parametric oscillators [1] and electro-optic Bragg gratings [2]. Recently, sub-micron domain engineering in waveguides has drawn much attention because of the possibility of implementing it in tunable Bragg grating structures [3]. To date, electric field poling is the most popular technique to produce periodically poled lithium niobate (PPLN). On the other hand, a direct-write electron beam poling technique appears as a promising alternative method since it does not include lithography and has a very high spatial resolution (5nm) [4]. For more efficient and stable functioning of PPLN devices, it is advantageous to fabricate waveguides rather than using bulk LiNbO3. Techniques based on diffusion processes such as proton exchange [5] have been extensively studied in combination with a PPLN structure. Thin film waveguide fabrication techniques, however, provide attractive advantages such as the ability to create a step index profile and suitability for integration with other processes. Among them, liquid phase epitaxy (LPE) is a very promising technique to produce high quality thin film waveguides of several-micron thickness with excellent crystallinity and surface morphology [6-9]. In this paper, we report the possible advantage of combining a direct-write e-beam and LPE LiNbO3 to achieve a submicron periodic domain structure. Around 400nm width domains with a quite regular period was obtained in LPE LiNbO3 films, which
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could not be fabricated in a single crystal congruent LiNbO3. The films on substrates with oppositely oriented domains were also domain engineered with an e-beam. To elucidate underlying p
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