Ding-Yu Shen

Monomode optical waveguide in lithium niobate formed by MeV Si+ ion implantation

The monomode enhanced-index LiNbO3 waveguide fabricated by low-dose ion implantation is reported. LiNbO3 crystals were implanted with 3 MeV Si+ ions to doses around 1014 ions/cm2. After annealing, the waveguides were formed by the extraordinary refractive index enhancement in the waveguide regions. The effective extraordinary refractive index of the waveguide increased with ion implantation dose. The loss was 0.64 dB/cm in the X-cut sample with an implantation dose of 3.3×1014 ions/cm2. The scattering loss in the Z-cut samples was even lower than that in the X-cut samples.The monomode enhanced-index LiNbO3 waveguide fabricated by low-dose ion implantation is reported. LiNbO3 crystals were implanted with 3 MeV Si+ ions to doses around 1014 ions/cm2. After annealing, the waveguides were formed by the extraordinary refractive index enhancement in the waveguide regions. The effective extraordinary refractive index of the waveguide increased with ion implantation dose. The loss was 0.64 dB/cm in the X-cut sample with an implantation dose of 3.3×1014 ions/cm2. The scattering loss in the Z-cut samples was even lower than that in the X-cut samples.

Optical waveguides formed in Nd:YVO4 by MeV Si+ implantation

The planar waveguide has been fabricated in a Nd:YVO4 crystal by 3.0 MeV Si+ ion implantation at a dose of 1×1015 ions/cm2 at room temperature. The waveguide was characterized by the prism-coupling method. The dark modes are measured before and after the annealing at 240 °C for 60 min in air. The refractive index profile is reconstructed using reflectivity calculation method. It is found that relatively large positive change of ordinary refractive index happens in the guiding region, which is quite different from most of the observed ion-implanted waveguides. The TRIM’98 code is carried out to simulate the energy loss during the implantation in order to obtain a better understanding for the waveguide formation.

Optical properties of stoichiometric LiNbO3 waveguides formed by low-dose oxygen ion implantation

The planar waveguides in z-cut stoichiometric LiNbO3 crystal have been fabricated by 3.0 MeV oxygen ion implantation with the dose of 6×1014ions∕cm2 at room temperature. The modes of the waveguides were measured by the prism-coupling method with the wavelength 633 and 1539 nm, respectively. The refractive index profiles of the waveguides were reconstructed using reflectivity calculation method. The Rutherford backscattering/channeling technique was used to investigate the damage produced by the ion implantation, the minimum yield of the spectra was 4.52%. The propagation loss of waveguide was 0.61 dB/cm obtained by fiber probe technique. It was found that positive changes of extraordinary refractive indices happened in the guiding regions, and such change increased after the annealing treatment at 260 °C for 60 min.

Monomode optical waveguide excited at 1540 nm in LiNbO(3) formed by MeV carbon ion implantation at low doses.

The monomode enhanced-index LiNbO(3) waveguide excited at 1540 nm is reported. X-cut LiNbO(3) crystals were implanted at room temperature by 6.0 MeV C(3+) ions with a dose of 2.0x10(15) ions/cm(2). Low loss planar optical waveguides were obtained and characterized by the prism coupling technique. Four dark modes were observed for extraordinary light at 633 nm, while only one enhanced-index mode was observed at 1540 nm. The propagation loss of the waveguide is 1.01 dB/cm measured with the moving fiber method. Reflectivity calculation method (RCM) was applied to simulate the refractive index profiles in waveguide. The width of waveguide structure induced by carbon ion implantation is ~3.6 microm.

Planar optical waveguides in β-BaB2O4 produced by oxygen ion implantation at low doses

The planar waveguides have been fabricated in z-cut β-BaB2O4 crystal by 2.2MeV O+ ion implantation at doses ranging from 5×1012 to 5×1014ions∕cm2 at room temperature. The waveguides were characterized by the prism-coupling method. Monomode, nonleaky planar waveguides at λ=633nm in β-BBO single crystals were fabricated at doses from 5×1012 to 2×1013ions∕cm2, and two mode and three mode waveguides were fabricated at doses from 4×1013 to 5×1014ions∕cm2, respectively. The refractive index profiles of the waveguides are reconstructed using reflectivity calculation method. The propagation loss of the measured ion implanted waveguide was about 1.6dB∕cm. It was found that positive changes of extraordinary refractive indices happened in the guiding regions, and such changes increased with the doses, which were different from most of the observed ion-implanted waveguides.

Ion-implanted waveguides in Nd3+-doped silicate glass and Er3+/Yb3+ co-doped phosphate glass

The data are presented on the waveguides formation in the Nd 3þ -doped silicate glass and Er 3þ /Yb 3þ co-doped phosphate glass by the implantations of He þ or Si þ ions, respectively. The prism-coupling method is used to measure the effective refractive indices of the waveguide dark modes. The refractive index profiles of the waveguides are reconstructed by using the reflectivity calculation method (RCM) and a comparison of such profiles among the different waveguides has been made. The reasons for the formation of the present waveguides are analyzed in a primary way. # 2002 Elsevier Science B.V. All rights reserved.

Low-loss optical planar waveguides in YVO4 produced by silicon ion implantation at low doses

Planar waveguides in x-cut YVO4 crystals were produced by ion-implanted Si+ ions with energies from 2.6 to 3.0 MeV at doses of 1×1013−1.5×1014 ions/cm2. The number of propagation modes varied from 1 to 3 as the doses of the implanted ions increased. The effective refractive indices of all the observed waveguide modes were higher than the refractive index of the substrate, which meant an index-enhanced guiding layer with thickness of ∼2 μm formed to confine the light propagation. The minimum propagation loss of the measured YVO4 waveguide was 0.27 dB/cm after annealing under suitable conditions.

Ion-implanted Nd:YVO 4 planar waveguide: refractive-index characterization and propagation mode reduction

We report for what is believed to be the first time planar waveguide formation and propagation mode reduction in Nd:YVO(4) crystal, which were achieved by 3.0-MeV silicon-ion implantation followed by annealing under specific conditions. After the implantation, an enhanced refractive-index region was formed with a width of ~2microm beneath the sample surface to act as a waveguide structure. We found that there were four propagation modes for the as-implanted Nd:YVO(4) waveguide, whereas after annealing at 240-360 degrees C for several hours the number of modes could be reduced to three, two, and one. After annealing at 400 degrees C for 1 h the monomode waveguide was destroyed completely, and no mode was observed in the sample.

Damage production in silicon by MeV Si cluster irradiation

We have accelerated clusters of Cn+ (n = 2–8), Aln+ (n = 2–4), Sin+ (n = 2–4) and Gen+ (n = 2, 3) to MeV energies at the 1.7 MV tandem accelerator of Peking University. The defect concentrations produced by cluster irradiation were measured by channelling Rutherford backscattering (CRBS). We took notice of the fact that the defect concentration depends significantly on the dose rate at the same energy and dose. In order to compare the defect density produced by Sin+ irradiation, irradiation at the same dose rate for different cluster sizes was preferred. The non-linear effect of defect concentration produced by Sin+ irradiation in the near surface region has been measured. Defect self-annealing for Si2 and enhanced defect production for Si3 are observed. This behaviour is well described by Tombrellos model for defect production by heavy ions in metals.

Optical Waveguide in X-Cut LiNbO3 Crystals by MeV P+ Ion Implantation with Low Dose

The X-cut, Y-propagation LiNbO 3 crystals were implanted by 2.8 MeV P + ions with doses of ∼1 x 10 14 ions/cm 2 at room temperature. Planar optical waveguides were formed by P + implantation at doses of 1 × 10 14 , 2 × 10 14 . 3 × 10 14 and 4 x 10 14 ions/cm 2 . Contrary to high-dose ion-implanted waveguides, the extraordinary refractive index was found to increase in the guide region for implantation with low doses by the dark mode. When the light beam was coupled to the LiNbO 3 waveguide which was formed by MeV P + implantation at a dose of 1 x 10 14 ions/cm 2 and a following annealing at 200 °C for 30 min in air, obvious light was found propagating through the entire length of the waveguide, and Rutherford Backscattering (RBS)/channeling technique was used to characterize the lattice reconstruction of LiNbO 3 crystals after the annealing treatment.