[Show abstract][Hide abstract] ABSTRACT: Strip-loaded waveguides were fabricated by the direct oxidation of a titanium film based on the single-crystal lithium niobate. The method avoided the surface roughness problems that are normally introduced during dry etching of waveguide sidewalls. Propagation modes of the composite strip waveguide were analyzed by a full-vectorial finite difference method. The minimum dimensions of the propagation modes were calculated to be 0.7 μm2 and 1.1 μm2 for quasi-TM mode and quasi-TE mode at 1550 nm when the thickness of the LN layer and TiO2 strip was 660 nm and 95 nm, respectively. The optical intensity was as high as 93% and was well confined in the LN layer for quasi-TM polarization. In this experiment, the propagation losses for the composite strip waveguide with 6 μm wide TiO2 were 14 dB/cm for quasi-TM mode and 5.8 dB/cm for quasi-TE mode, respectively. The compact hybrid structures have the potential to be utilized for compact photonic integrated devices.
[Show abstract][Hide abstract] ABSTRACT: We report low-loss channel waveguides in a single-crystal LiNbO(3) thin film achieved using the annealed proton exchange process. The simulation indicated that the mode size of the α phase channel waveguide could be as small as 1.2 μm(2). Waveguides with several different widths were fabricated, and the 4 μm-wide channel waveguide exhibited a mode size of 4.6 μm(2). Its propagation loss was accurately evaluated to be as low as 0.6 dB/cm at 1.55 μm. The single-crystal lattice structure in the LiNbO(3) thin film was preserved by a moderate annealed proton exchange process (5 min of proton exchange at 200°C, followed by 3 h annealing at 350°C), as revealed by measuring the extraordinary refractive index change and x ray rocking curve. A longer proton exchange time followed by stronger annealing would destroy the crystal structure and induce a high loss in the channel waveguides.
[Show abstract][Hide abstract] ABSTRACT: The proton exchanged (PE) planar and channel waveguides in a 500 nm thick single-crystal lithium niobate thin film (lithium niobate on insulator, LNOI) were studied. The mature PE technique and strong confinement of light in the LN single-crystal thin film were used. The single mode and cut-off conditions of the channel waveguides were obtained by finite difference simulation. The results showed that the single mode channel waveguide would form if the width of the PE region was between 0.75 μm and 2.1 μm in the β4 phase. The channel waveguide in LNOI had a much smaller mode size than that in the bulk material due to the high-refractive-index contrast. The mode size reached as small as 0.6 μm2 in simulation. In the experiment, the refractive index and phase transition after PE in LNOI were analyzed using the prism coupling method and X-ray diffraction. Three different width waveguides (5 μm, 7 μm and 11 μm) were optically characterized. Near-field intensity distribution showed that their mode sizes were 3.3 μm2, 5 μm2 and 7 μm2. The propagation losses were evaluated to be about 16 dB/cm, 12 dB/cm and 11 dB/cm, respectively. The results indicate that PE is a promising method for building more complicated photonic integrated circuits in single-crystal LN thin film.
[Show abstract][Hide abstract] ABSTRACT: High-refractive-index contrast, single-crystal lithium niobate thin films are emerging as a new platform for integrated optics. Such lithium niobate thin films are prepared using ion implantation and direct-wafer bonding to a SiO2 layer deposited on a LN substrate. However, the ion-implantation process can cause changes in the refractive index and result in lattice damage, and there are few studies on the optical and structural properties of lithium niobate thin film to compensate for this. In this paper, we reported that the refractive index of lithium niobate thin film can reach that of the bulk material by annealing in an oxygen atmosphere at 500 °C for 5 h. The experimental results of high-resolution X-ray diffraction (HRXRD) and Rutherford back-scattering spectrum (RBS) showed a good crystal lattice arrangement in the LN thin film. These experimental results confirmed that the refractive index and crystal-lattice structural properties of the lithium niobate thin film were similar to that of the bulk material. To demonstrate the application on integrated optics, a 1 μm wide photonic wire was fabricated and the near-field intensity profile at 1.55 μm wavelength was obtained and compared with the simulation result.
[Show abstract][Hide abstract] ABSTRACT: We report on a photonic crystal slab patterned on a 690 nm thick LiNbO<sub>3</sub> thin film bonded to SiO<sub>2</sub> on lithium niobate substrate. The transmission spectrum is measured and a broad and clear photonic bandgap ranging from 1335 to 1535 nm with a maximum extinction ratio of more than 20 dB is observed. The bandgap is simulated by plane wave expansion and 3D finite-difference time-domain methods. Such a deep and broad bandgap structure can be used to form high-performance photonic devices and circuits on the platform of lithium niobate-on-insulator.
[Show abstract][Hide abstract] ABSTRACT: Single-mode optical waveguides in LiNbO<sub>3</sub> substrate with loss as low as 0.17dB/cm were fabricated by a multi-energy low-dose ion implantation technology and cumulative annealing treatment. A waveguide Y-Branch splitter was demonstrated. Index profile in waveguide is described based on the ion implantation-induced damage profile, and propagation property in waveguide is simulated. Simulation results show a good consistence with the measured ones.
[Show abstract][Hide abstract] ABSTRACT: The Li Nb O <sub>3</sub> planar optical waveguides are fabricated by 3.0- MeV C <sup>+</sup> ion implantation at the doses of 1.5–10.5×10(14) cm <sup>-2</sup> . Both TE and TM modes are observed by prism coupling method ( m lines). The reconstructed refractive index profiles of the guiding region show that extraordinary index has an enhancement compared with the substrate of Li Nb O <sub>3</sub> , while ordinary index experiences a typical “barrier” change. The modal analysis of the waveguides shows a good confinement of light in fundamental TM mode. The tendency of effective refractive index (decrease after the annealing for TE and increase after annealing for TM) suggests a moderate recovery of the lattice.
[Show abstract][Hide abstract] ABSTRACT: NdLiP4O12 crystals can be used for low-threshold, miniature laser. A double waveguide structure in a NdLiP4O12 laser crystal formed by ion implantation is for the first time reported. Double waveguide in NdLiP4O12 laser crystal is formed with 2.8 and 1.8MeV He ions to the same dose of 1.5×1016 He ions/cm2. The refractive index distribution of the double waveguide in the NdLiP4O12 laser crystal is given based on the reflectivity calculation method.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 01/2005; 227(3):271-274. DOI:10.1016/j.nimb.2004.08.017 · 1.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Low-energy 120 and 150 keV H+ was implanted in z-cut LiNbO3 at room temperature. The fluence of H+ is 5x10(16) ions/cm(2) . The damage profiles in LiNbO3 induced by implantation were investigated using Rutherford backscattering/channelling. The damage profiles were extracted using the channelling results. The experimental damage profiles in LiNbO3 were analyzed and compared to the simulated results from TRIM. The results show a good consistency between experimental and simulated results. The present results are useful for the fabrication of H-implanted waveguides of oxide crystals, especially LiNbO3 .
Radiation Effects and Defects in Solids 05/2004; 159(5):309-314. DOI:10.1080/10420150410001670279 · 0.51 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: AlN films with thickness from 100 to 1000 nm were grown on SiC substrate by MBE. AlN crystalline films were doped by implantation with 160 keV Tb ions to fluences of 5×1014, 1.5×1015, 3×1015 and 6×1015 ions/cm2, respectively. The damage profiles in AlN films induced by Tb implantation were investigated using RBS/channeling technique. A procedure developed by Feldman and Rodgers was used to extract damage profile by considering the dechanneling mechanism of multiple. The comparison of the extracted profile with TRIM prediction shows a significant difference in the shape and in the position of damage profile. The damage profile in AlN film is similar as Tb distribution. The RBS/channeling of Tb-implanted AlN film before and after 950 °C annealing treatments show a good consistency, which indicate that high temperature annealing cannot result in a significant change in both crystal damage and in Tb distribution.
[Show abstract][Hide abstract] ABSTRACT: The 400keV Er and Nd ions were implanted into Si1N1.375H0.603, each kind of ions were performed at 0 and 60° incident angles, respectively. The mean projected ranges as well as range straggling and lateral spread of implanted ions were studied by using Rutherford backscattering (RBS) of 2.1MeV He ions. The obtained experimental values were compared with the calculated values by TRIM’96. The results show that ranges are in good agreement with each other; for range straggling and lateral spreads the maximum difference between the experimental and calculated values are 22 and 21%, respectively.
[Show abstract][Hide abstract] ABSTRACT: YCa4O(BO3)3 (YCOB) is one of the rare-earth calcium oxyborate family of crystals. The crystal has good potential to be used for self-frequency doubling due to its excellent combination of nonlinear and laser properties. We have used MeV He+ ions to make waveguides in YCOB and Nd:YCOB (NdYCOB) crystals. The ion implantation was carried out with 2.8 MeV He+ ions at room temperature. The fluences have varied from 1.5×1016 to 5.5×1016 ions/cm2. The model 2010 prism coupler was used to measure the modes in YCOB and NdYCOB waveguides formed by MeV He+ ion implantation. The refractive index profiles are fitted based on the reflectivity calculation method. We have used TRIM'98 simulation to get the range and damage profiles by MeV He+ ions in YCOB. Especially the refractive index change as a function of fluence is discussed.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 05/2002; 191(1):789-793. DOI:10.1016/S0168-583X(02)00654-7 · 1.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: High quality BaTiO3 optical-waveguide thin films on MgO(100) substrate were fabricated successfully by using pulsed laser deposition technique. The properties of the samples were characterized by using Rutherford backscattering (RBS), X-ray diffraction, atomic force microscopy and prism coupling method. The RBS shows no obvious evidence for interdiffusion between the film and the substrate. The thickness of the film and the Ba/Ti ratio were calculated based on RBS to be 881 nm and 1.004, respectively. X-ray diffraction results show that the as-deposited BaTiO3 film is basically oriented polycrystalline, and strong (l00) peaks were revealed. The root mean square (rms) roughness of the film was evaluated to be 0.796 nm, this is only 0.1% of the film thickness. The bright TE (m=0,1,2,3) and TM (m=0,1,2,3) modes in the BaTiO3 film optical waveguide were observed.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 05/2002; 191(1):778-782. DOI:10.1016/S0168-583X(02)00652-3 · 1.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The first MeV copper and nickel ion implanted waveguides in Nd:NaY(WO4)2 are reported. The planar optical waveguides were formed in this crystal by 2.8 MeV Cu+ or Ni+ ion implantation with doses of 1–3×1015 ions/cm2 at room temperature, respectively. The dark modes were observed by prism coupling method. The reflectivity calculation method was used to analyze the refractive index profiles of the waveguides.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 04/2002; 187(4):475-478. DOI:10.1016/S0168-583X(01)01158-2 · 1.12 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: KTiOPO4 samples were implanted by Bi+ ions with energies from 100 to 350 keV in increments of 50 keV. The depth distribution and diffusion behavior of implanted Bi+ into KTiOPO4 were investigated by normal and oblique incidence Rutherford backscattering. The results show that the maximum difference between experimental and calculated values of the mean projected range is less than 22% the experimental range straggling somewhat deviates from the prediction by TRIM'98. After annealing, the redistributions of implanted Bi+ ions in KTiOPO4 do not obey Fick's law, and there is a segregation process to the surface for 700 °C annealing. After 800 °C annealing for 30 min, most of the segregated Bi+ ions had evaporated, and the distribution of the remaining Bi+ ions became flat.
Journal of Vacuum Science & Technology A Vacuum Surfaces and Films 03/2002; 20(2):362-365. DOI:10.1116/1.1446449 · 2.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 2.0 MeV Au+ ions were implanted into different Si substrates with a fluence of 2× 1015 ions/cm2 at room temperature with different angles of incidence. Tested Si substrates are amorphized Si, amorphous Si film and crystal Si. The mean projected range, range straggling and lateral spread have been studied by Rutherford backscattering (RBS). The results show that (1) the experimental mean projected range is larger than the value predicted by TRIM (transport of ions in matter) by around 20%; (2) the experimental range straggling and lateral spread deviate significantly from the TRIM predictions; (3) after the correlation between nuclear and electronic stopping is included, the agreement between experimental and calculated values is markedly improved.
Japanese Journal of Applied Physics 02/2002; 41(2A):918-921. DOI:10.1143/JJAP.41.918 · 1.13 Impact Factor