Structure-changed third-order optical nonlinearity in CaCu3Ti4O12 thin films grown on MgO(111) substrates
Introduction
Thin films of excellent third-order optical nonlinearity are essential for integrated all-optical processing devices, such as switching, computing, storage and communication [1]. Comparing with bulk materials, the linear and nonlinear optical properties of thin films can be flexibly modulated by introducing atom composition deviation, interface effects, and orientation of crystallization during the fabrication [[2], [3], [4], [5], [6], [7], [8]]. Especially, the integrated photonic devices may be fabricated on different substrates, which lead to different growth orientation of films due to lattice mismatch. Over the past few years, the third-order optical nonlinearity in films grown on various substrates of different crystallization states, e.g. amorphous [3,9], polycrystalline [10,11], preferred orientation [12,13], nanocrystalline doped in matrices [5,14], were intensively studied. Fruitful results were obtained. However, few reports are on the comparison of the optical nonlinearity in the same materials of different crystallization states [8,13]. Considering the application of nonlinear films, the detailed study on the effect of film structures on the optical nonlinearity has practical significance for the integrated photonic devices.
Calcium copper titanate (CaCu3Ti4O12, CCTO) film with perovskite-like structure of high dielectric permittivity for microelectronics [15,16], photochemistry [[17], [18], [19]] and large third-order optical nonlinearity has drawn much attentions [8,12]. The nonlinear refraction in CCTO originates from the d-orbital between transition metal and oxygen, i.e. Ti-O and Cu-O, and determined by the bond length quadratically [12]. The bond length between transition metal and oxygen can be modulated by lattice mismatch between the film and substrate, and thus to change the nonlinear refraction. In our previous studies, we have reported the optical nonlinearity in the films deposited on different substrates, e.g. LaAlO3 (0001), MgO (002) and fused silica (SiO2) substrates, of different preferred growth orientation [8,12]. The negative nonlinear refractive index γ2 of different values ∼10−14 m2/W was obtained in those films. The two-photon absorption in the films grown on MgO(002) substrates while the saturable absorption in the films on LaAlO3 (0001) and fused silica substrates were observed. The results indicate that the optical nonlinearity is indeed affected by the structure of film. In this paper, we further deposited CCTO films on MgO(111) substrates, and the CCTO films of (220) orientation are obtained. The self-focusing behavior in CCTO films of positive nonlinear refraction was first observed, which is different from the films grown on aforementioned substrates of self-defocusing behavior. The nonlinear refraction coefficient, along with the nonlinear saturable absorption intensity is determined.
Section snippets
Experimental method
The CCTO films were grown on single crystal double-polished (111) MgO substrates by pulsed laser deposition technique. The processes are almost the same as we reported [8,12]. Briefly, a XeCl excimer laser beam (308 nm, 27 ns, 4 Hz) was focused onto a CCTO target with a typical energy about 2 J/cm2. The films were deposited under 30 Pa of O2 at 800 °C, followed by annealing for 30 min at the deposition temperature in 1 atm oxygen. The thickness of films was controlled by deposition time, and
Results and discussion
The crystallization of a CCTO film on an MgO (111) substrate is shown in Fig. 1. The diffraction angles at 34.26° and 72.18° correspond to Miller indices (220) and (440) of CCTO, respectively, indicating that the CCTO film has a (220)-preferred orientation. The lattice parameters can be calculated using Bragg’s law nλ=2dhkl sinθ with n an integer, λ the wavelength of X-ray, θ the incident angle of X-ray to the surface of sample, and dhkl the inter-planar spacing with indice (hkl). The lattice
Conclusions
In summary, we investigated the optical nonlinearity of the CCTO thin films of (220)-orientation grown on MgO(111) using Z scan technique at a wavelength of 532 nm with the pulse duration of 25 ps. The nonlinear saturable absorption coefficient, saturable intensity and modulation depth was determined, and suitable for high-power mode-lock laser. The large positive third-order nonlinear refraction of value 0.76 cm2/GW and negative fifth-order nonlinear refraction of value -0.2 cm4/GW2 were
Funding
We acknowledge the financial support from the National Natural Science Foundation of China (Grant No. 11404195) and China Postdoctoral Science Foundation (Grant No. 2015M582127).
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
References (39)
- et al.
Nonlinear optical properties in SrTiO3 thin films by pulsed laser deposition
Solid State Commun.
(2005) - et al.
Enhanced nonlinear optical responses of materials: composite effects
Phys. Rep.
(2006) - et al.
Structural, optical and femtosecond third-order nonlinear optical properties of LiNbO3 thin films
Mater. Res. Bull.
(2017) - et al.
Large third-order optical nonlinearity of ZnO-Bi2O3-B2O3 glass-ceramic containing Bi2ZnB2O7 nanocrystals
J. Eur. Ceram. Soc.
(2014) - et al.
High Dielectric Constant in ACu3Ti4O12 and ACu3Ti3FeO12 Phases
J. Solid State Chem.
(2000) - et al.
Giant dielectric constant response in a copper titanate
Solid State Commun.
(2000) - et al.
Oxygen vacancies induced visible-light photocatalytic activities of CaCu3Ti4O12 with controllable morphologies for antibiotic degradation
Appl. Catal. B
(2018) Nonlinear Optics
(1992)Pulsed Laser Deposition of Thin Films: Applications-Led Growth of Functional Materials
(2006)- et al.
Third-order optical nonlinearity in nonstoichiometric amorphous silicon carbide films
J. Alloys. Compd.
(2019)
Strong optical nonlinearity of the nonstoichiometric silicon carbide
J. Mater. Chem. C Mater. Opt. Electron. Devices
Thermo-optic effect and optical nonlinearity in nc-Si embedded in a silicon-nitride film
Opt. Express
Effect of structure on nonlinear optical properties in CaCu3Ti4O12 films
J. Appl. Phys.
Third-order optical nonlinearity in silicon nitride films prepared using magnetron sputtering and application for optical bistability
J. App. Phys.
Giant optical nonlinearity of a Bi2Nd2Ti3O12 ferroelectric thin film
Appl. Phys. Lett.
Large nonlinear optical response of polycrystalline Bi3.25La0.75Ti3O12 ferroelectric thin films on quartz substrates
Opt. Lett.
Large optical nonlinearity in CaCu3Ti4O12 thin films
Appl. Phys. A
Efficient Solar Energy Conversion Using CaCu3Ti4O12 Photoanode for Photocatalysis and Photoelectrocatalysis
Sci. Rep.
Effect of thickness on humidity sensing properties of RF magnetron sputtered CaCu3Ti4O12 thin films on alumina substrate
IEEE Sens. J.
Cited by (6)
Third- and fifth-order optical nonlinearity in PbO-BaO-Na<inf>2</inf>O-Nb<inf>2</inf>O<inf>5</inf>-SiO<inf>2</inf> glass and glass-ceramic nanocomposite dielectrics
2021, OptikCitation Excerpt :The third-order optical nonlinearity of the samples was studied by a single-beam Z-scan method. The experimental setup is the same as that used in Refs. [18–20]. A Nd:YAG mode-locked laser (1064 nm, 25 ps, 1 Hz) was used as the light source.
Third-order optical nonlinear properties of Co-doped V<inf>2</inf>O<inf>5</inf> nanoparticles
2021, OptikCitation Excerpt :Over the recent years, many efforts have been devoted to seek for new nonlinear optical (NLO) materials with ultrafast response and superior third-order nonlinearity for optoelectronics applications. Among them, transition metal oxides with different morphological structures have been proved to be promising materials for developing novel photonic devices utilizing their nonlinear optical properties [1–5]. Vanadium pentoxide (V2O5), the most stable member of vanadium oxides series, is a well-studied semiconductor owing to its interesting multifunctional properties granting several applications in optical [6,7], electrical [8,9], chemical [10–12], electrochemical and thermochromics fields [13,14].