Anisotropic Gap Structure and Sign Reversal Symmetry in Monolayer Fe(Se,Te).

The iron-based superconductors are an ideal platform to reveal the enigma of the unconventional superconductivity and potential topological superconductivity. Among them, the monolayer Fe(Se,Te)/SrTiO3(001), which is proposed to be topological nontrivial, shows interface-enhanced high-temperature superconductivity in the two-dimensional limit. However, the experimental studies on the superconducting pairing mechanism of monolayer Fe(Se,Te) films are still limited. Here, by measuring the quasiparticle interference in monolayer Fe(Se,Te)/SrTiO3(001), we report the observation of the anisotropic structure of the large superconducting gap and the sign change of the superconducting gap on different electron pockets. The results are well consistent with the "bonding-antibonding" s±-wave pairing symmetry driven by spin fluctuations in conjunction with spin-orbit coupling. Our work is of basic significance not only for a unified superconducting formalism in the iron-based superconductors, but also for understanding of topological superconductivity in high-temperature superconductors.

Optical planar waveguide fabricated in Nd:LuVO4 crystal by MeV oxygen implantation.

We report the first time optical planar waveguide fabricated in vanadate laser crystal Nd:LuVO4 by 3.0 MeV oxygen ion implantation with the dose of 6x1014 ions/cm2 at room temperature. After the implantation, an enhanced ordinary refractive index region was formed with a width of about 2.1 microm beneath the sample surface to act as a waveguide structure. The modes were observed at 633 nm, while only one mode was observed at 1539 nm after annealing at 300 degrees C for 60 min in air. The changes of ordinary refractive index in the guiding region were about 4.42% and 4.07% before and after annealing.

Investigation and analysis of a single-mode waveguide formed by multienergy-implanted LiNbO3.

We demonstrate a single-mode waveguide in LiNbO3 by use of both prism and end-face coupling methods. The waveguide is formed by multienergy megaelectron-volt O2+ implantation at room temperature. A bright line is observed only when moderate postimplant annealing was performed. The possible index profile of the waveguide is constructed according to the damage profile of the lattice structure caused by the implantation. Although dark-mode measurement shows that the effective extraordinary index of LiNbO3 is raised in the waveguide layer, results of the analysis indicate that the single guiding mode could be supported by a synergetic effect from both the raised index layer and the low-index barrier. The reduced loss of the waveguide can be attributed to the widened low-index barrier from multienergy implantation.

Lithium niobate channel waveguide at optical communication wavelength formed by multienergy implantation.

Channel waveguides at 1540 nm in X- and Z-cut LiNbO3 are formed by one-step multienergy MeV O2+ implantation. Single perpendicular mode in both planar and channel waveguides is demonstrated. In the ne channel waveguide, double transverse modes are observed because of the large index difference and broad width of the channel. A single transverse mode is obtained in the no channel waveguide. The thickness of the waveguide is less than 2 mum, and the compactness of the waveguide is attributed to the large index difference between the guiding region and the low-index barrier. The mode patterns and the waveguide loss are measured and analyzed. The loss of 0.9 and 0.7 dB/cm are obtained from the no and ne channel waveguides, respectively.

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.

Low propagation loss of the waveguides in fused quartz by oxygen ion implantation.

The planar waveguides have been fabricated in fused quartz by 3.0 MeV oxygen ion implantation at dose of 1x10;15 ions/cm2. The guiding modes were observed at wavelengths of both 633 nm and 1539 nm before and after annealing at 320 masculineC, 450 masculineC and 500 masculineC in 60 min characterized by the prism-coupling method. The width of the waveguide structure induced by oxygen ion implantation is about 3 microns. After suitable annealing, the minimum propagation loss of the waveguide in fused quartz can be reduced to -0.14 dB/cm.

Low propagation loss of the waveguides in fused quartz by oxygen ion implantation: errata.

The calculated data of propagation loss of the waveguide were incorrect. Corrected data show the actual results in the measurements.

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.