Yu-Jie Ma

Theoretical modeling and experiment of refractive index change in He + ion-implanted KTP waveguide

A theoretical model is presented to explain the refractive index change in the ion-implanted KTP waveguide, which includes respective contributions of spontaneous polarization, molar polarization and molar volume, and photoelastic effect. Numerical calculations of refractive indices along different crystalline orientations (X, Y, and Z) as a function of the lattice damage level, determined by Rutherford back-scattering/channeling technique, are performed based on the results from a set of z-cut KTP crystals implanted by 300 keV He+ ions in doses ranging from 4×10(16) to 8×10(16) ions/cm2. The theoretical results show consistency with the experimental data. To our knowledge, this is the first model to comprehensively describe the ion-implanted KTP planar waveguide.

Optical confinement achieved in ZnO crystal by O + ions implantation: analysis of waveguide formation and properties

Optical confinement in ZnO crystal was observed by O(+) implantation with different MeV energies and doses. Planar optical waveguides were formed in the as-implanted ZnO samples. The optical properties of the planar waveguide were investigated by the prism-coupling and the end-face coupling methods at the wavelength of 633 nm. The crystal lattice damage in the guiding region caused by the O(+) ions implantation was analyzed by the Rutherford backscattering/Channeling technique, results show that even high dose at 2 × 10(15) ions/cm(2) can hardly produce defect in near surface of ZnO. A theoretical model is developed to explain the principle of waveguide formation in ZnO crystal and the refractive index profile in the implanted waveguide was reconstructed accordingly. The experimental result and analysis are significant for application of ZnO crystal, especially for the design of ZnO light emitter devices.

Theoretical modeling of refractive index in ion implanted LiNbO3 waveguides

A theoretical model is developed to evaluate the roles of various mechanisms, including the molar polarization and molar volume, the spontaneous polarization and the photoelastic effect, for the modifications of refractive indices in ion-implanted LiNbO3 waveguides. Based on the model, numerical calculations of refractive indices as a function of the lattice damage level in LiNbO3 crystals of different crystalline orientations (X, Y, and Z), are performed, with results in a good agreement with experimental data. The analysis indicates that the spontaneous polarization, the molar polarization, and molar volume play important roles in determining the index profiles in ion implanted LiNbO3. In addition, the contribution of the strain-induced photoelastic effect has been identified for different damage levels.

Analysis of Si + -implanted Nd:YVO 4 crystal: the relation between lattice damage and waveguide formation

We report the lattice damage and annealing properties of the 500 keV Si+ ions implanted Nd:YVO4 crystal with different doses. The Rutherford backscattering spectrometry/channeling technique was used to analyze the damage profiles of ion-implanted samples. A series of post-implant annealing was performed at temperatures from 250 °C to 400 °C to investigate the relation between lattice damage profile and the waveguide formation. Implantations at doses of more than 5×10(14) ions/cm2 can result in high damage ratio in the near-surface region and the lattice structure cannot be restored even after annealing at 400 °C. Such seriously damaged lattice is relatively stable and contributes to the waveguide structure. Convergence of the refractive index at the surface region after ion implantation is believed mainly due to the elastic collisions with the target atoms caused by nuclear energy loss.

Refractive index profile in ion-implanted neodymium-doped yttrium vanadate waveguide: the relation between index change and lattice damage

Abstract. A model is presented to explain the refractive index changes in the ion-implanted neodymium-doped yttrium vanadate waveguide region, which is helpful for characterizing index profile dependence on implantation parameters. It indicates that the lattice damage is the main factor for the refractive index changes. Waveguide structure is formed mainly due to an increase of ordinary refractive index in the ion-implanted region. The theoretical results based on this model are in good agreement with the experimental data from 500 keV Si+ ion implantations and keV He+ ion implantations.

Theoretical investigation of quasiparticle band structures and optical spectra of large-diameter semiconducting single-walled carbon nanotubes

Using ab initio many-body perturbation theory (within GW approximation and Bethe-Salpeter equation), including electronic exchange, correlation, and electron-hole interaction effects, we study the optical properties of large-diameter semiconducting single-walled carbon nanotubes (SWCNTs). The calculated energies of the lowest two optically allowed transitions (E11 and E22) agree well with those deduced from experiments. The lowest optical allowed transition of these tubes is between the first two van Hove singularities on each side of the Fermi level, which is different from that of small-diameter tubes. The exciton binding energy for E11 is calculated, which is consistent with that of the experiments.

The Damage Analysis of Nd:YVO4 Crystal Implanted by He+ Ions at Low Energy

We report the damage properties of the He⁺ ions implanted Nd:YVO₄ crystal. Implantation was carried out at room temperature by He+ ions at the doses of 1×10¹⁶, 2×10¹⁶, and 4×10¹⁶ ions/cm² with the energy of 200keV. The depth of the damage region is about 0.85μm beneath the surface. Rutherford backscattering spectrometry (RBS)/channeling technique was used to investigate the damage profile of ions implanted samples. Low atomic displacement ratio in as-implanted samples indicates a high irradiative resistance of YVO₄ crystal and the dynamic annealing effect of He⁺ ions in the implantation process. Post-implant annealing was performed for all the samples at 200°C and 300°C for an hour, respectively. The height and width of damage peak decreased somewhat after annealing at 200°C. Repairing and re-crystallization of damaged lattice was achieved after annealing at 300°C. Photoluminescence of ion-implanted samples were measured to investigate effect of implantation on fluorescence properties of Nd³⁺. The damage on sample surface was analyzed by optical microscopy (OM) and atomic force microscopy (AFM).