Xiu-Hong Liu

Optical waveguides in TiO 2 formed by He ion implantation

We report on the formation and the optical properties of the planar and ridge optical waveguides in rutile TiO₂ crystal by He+ ion implantation combined with micro-fabrication technologies. Planar optical waveguides in TiO₂ are fabricated by high-energy (2.8 MeV) He+-ion implantation with a dose of 3 × 10¹⁶ ions/cm² and triple low energies (450, 500, 550) keV He+-ion implantation with all fluences of 2 × 10¹⁶ ions/cm² at room temperature. The guided modes were measured by a modal 2010 prism coupler at wavelength of 1539 nm. There are damage profiles in ion-implanted waveguides by Rutherford backscattering (RBS)/channeling measurements. The refractive-index profile of the 2.8 MeV He+-implanted waveguide was analyzed based on RCM (Reflected Calculation Method). Also ridge waveguides were fabricated by femtosecond laser ablation on 2.8 MeV ion implanted planar waveguide and Ar ion beam etching on the basis of triple keV ion implanted planar waveguide, separately. The loss of the ridge waveguide was estimated. The measured near-field intensity distributions of the planar and ridge modes are all shown.

Lithium Niobate Ridge Waveguides Fabricated by Ion Implantation Followed by Ion Beam Etching

A new fabrication method for lithium niobate ridge waveguides is reported. Lithium niobate ridge waveguide with a smooth surface was fabricated by O+ ions implanted combined with Ar ion beam etching. The beam propagation method (BPM) was used to simulate the properties of planar and ridge waveguides by use of a reconstructed refractive index profile. The simulation results match to the experimental results very well, and the loss value of the ridge waveguide is about 2 dB/cm.

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.

Optical properties of a single mode planar waveguide in Nd:YVO 4 fabricated by multienergy He ion implantation

We fabricated a single-mode planar waveguide in z-cut Nd:YVO(4) by multienergy He ion implantation in total fluence of 4.5×10(16) ions/cm(2) at room temperature and investigated optical properties of Nd:YVO(4) before and after He ion implantation by measuring transmission, confocal microluminescence, and confocal Raman spectra. Absorption bands and the photoluminescence features of the bulk Nd:YVO(4) crystal have been preserved after He ion implantation. In Raman spectra, most of the peak positions and peak widths had no obvious change before and after He ion implantation. The guiding mode and near-field image in the waveguide were measured by the prism coupling method and end-face coupling method, respectively. We investigated the damage behavior of a Nd:YVO(4) waveguide after implantation, annealing treatment by the Rutherford backscattering/channeling technique. The minimum yield of the virgin z-cut Nd:YVO(4) was 1.98%, which increased to 4.73% after He ion implantation and decreased to 3.20% after annealing at 600 K for 30 minutes.

Planar and ridge waveguides formed in LiNbO 3 by proton exchange combined with oxygen ion implantation

We report on the fabrication of planar and ridge waveguides in lithium niobate by proton exchange combined with oxygen ion implantation. The implanted energy ranges from 600 to 1400 keV with a dose of 1 x 10(15) ions/cm(2). The modes in proton exchanged waveguide can be modulated by O ion implantation. There are different damage profiles in proton-exchanged and ion-implanted waveguides in Rutherford backscattering/channeling spectra. The refractive index profile in single-mode waveguide in lithium niobate has been obtained based on Intensity Calculation Method. Also ridge waveguide was fabricated on the basis of planar waveguide by Ar ion beam etching. The measured near-field intensity distributions of the ridge waveguide modes show a reasonable agreement with the simulated ones. The estimated propagation loss was approximately 2.2 dB/cm.

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.

The Optical and Fluorescence Properties of Planar and Channel Waveguides in Laser Crystal Nd:SrGdGa

The planar and channel waveguides were fabricated by C ion implantation on Nd:SrGdGa3O7 crystal respectively. The guided modes and optical propagation properties were investigated by waveguide coupling method, and the simulation of the light propagation process was performed simultaneously for comparison. The propagation losses of planar and channel waveguides were 0.84 dB/cm and 0.5 dB/cm, respectively, which were measured by end-face coupling equipment. The confocal microfluorescence investigation was used to observe the influence of the C ion implantation process on the Nd ions properties. It shows that there are merits about the relative low loss and the good reservation of Nd ions fluorescence properties in the C-ion-implanted waveguide. Thus, this waveguide could be a very promising candidate for integrated optical device.

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We report on a single-mode waveguide in lithium niobate produced by 400?keV He ion implantation with a dose of 3 ? 1016?ions?cm?2 at liquid nitrogen temperature. Rutherford backscattering/channelling spectra have been measured in the waveguide before and after annealing and the damage profile has been extracted. The shape of the measured damage profile is similar to that of the ordinary refractive index by the intensity calculation method. The near-field intensity profile in a ridge waveguide is given and the propagation loss for the extraordinary index is estimated to be 1.9?dB?cm?1.

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A novel temperature demodulation method which eliminates the impact of Rayleigh scattering on Raman distributed temperature sensors (RDTS) using anti-Stokes light only is presented. This method utilizes two sections of reference fiber which are placed into temperature control chambers with different temperatures, such that the impact caused by the variation of laser’ power and the Rayleigh scattering is eliminated by the two reference temperatures. In the experiment, the temperature error caused by the Rayleigh scattering was decreased by 0.6℃ and 1.7℃ at 30℃ and 50℃compared with conventional method respectively.