Femtosecond laser micromachined ridge waveguide lasers in Nd:YAG ceramics

We report on the fabrication of ridge waveguides in Nd:YAG ceramic by using femtosecond laser micromachining of the surface of a He ion implanted planar waveguide. Under optical pump of 808 nm light, continuous wave waveguide lasers have been realized at 1.06 μm at room temperature in the Nd:YAG ceramic ridge waveguide system, reaching a maximum output power of 46 mW. The lasing threshold of ∼64.9 mW and the slope efficiency of 42.5% are obtained for the ridge waveguide system, which shows superior lasing performance to the Nd:YAG ceramic planar waveguide.The work is supported by the National Natural Science Foundation of China (No. 10925524), the Spanish Ministerio de Ciencia e Innovación (MICINN) through Consolider Program SAUUL CSD2007-00013, Project FIS2009-09522 and Junta de Castilla y León (Project SA086A12-2). S.Z. acknowledges the funding by the Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF-VHNG-713). Support from the Centro de L seres Pulsados (CLPU) is also acknowledged

Femtosecond laser micromachining of Nd:GdCOB ridge waveguides for second harmonic generation

We report on the fabrication of Nd:GdCOB ridge waveguides by using femtosecond laser micromachining of planar waveguides that were produced by carbon ion irradiation. The guiding properties of the Nd:GdCOB ridge waveguides are investigated. The second harmonic generation (SHG) at 532 nm green laser from ridges in a series of transverse widths is realized. The results show that the optical conversion efficiencies of SHG in the fabricated ridge waveguides are considerably enhanced with respect to the planar waveguide, and the maximum value reaches 11.4% under a pulsed 1064 nm laser pump.The work is supported by the National Natural Science Foundation of China (No. 10925524), the Spanish Ministerio de Ciencia e Innovación (MICINN) through Consolider Program SAUUL CSD2007-00013 and Project FIS2009-09522. S.Z. acknowledges the funding by the Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF-VH-NG-713). Support from the Centro de Láseres Pulsados (CLPU) is also acknowledged

Optical waveguides in LiTaO3 crystals fabricated by swift C5+ ion irradiation

We report on the optical waveguides, in both planar and ridge configurations, fabricated in LiTaO3 crystal by using carbon (C5+) ions irradiation at energy of 15 MeV. The planar waveguide was produced by direct irradiation of swift C5+ ions, whilst the ridge waveguides were manufactured by using femtosecond laser ablation of the planar layer. The reconstructed refractive index profile of the planar waveguide has showed a barrier-shaped distribution, and the near-field waveguide mode intensity distribution was in good agreement with the calculated modal profile. After thermal annealing at 260 °C in air, the propagation losses of both the planar and ridge waveguides were reduced to 10 dB/cm.This work is supported by the National Natural Science Foundation of China (No. U1332121) and the 973 Project (No. 2010CB832906) of China. S.Z. acknowledges the funding by the Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF-VHNG-713). J.R.V. thanks supports from Junta de Castilla y León under project SA086A12-2 and the Centro de Láseres Pulsados (CLPU)

Ridge Waveguides and Y-Branch Beam Splitters in KTiOAsO4 Crystal by 15 MeV Oxygen Ion Implantation and Femtosecond Laser Ablation

We report on the fabrication of ridge waveguides and Y-branch beam splitters in KTiOAsO 4 nonlinear optical crystal by the combination of 15 MeV oxygen (O 5+ ) ion implantation and femtosecond laser ablation. Guiding properties were investigated at the wavelengths of 633 and 808 nm, respectively, showing high polarization sensitivity of light propagation. Splitting ratios of these beam splitters are dependent on in-coupling alignment. The simulated guiding modal distributions of splitted guided beams, which was based on a reconstructed refractive index profile, shows reasonable consistence with the measured ones. After the stepwise annealing treatment at 473 and 573 K for 1 h each, the propagation losses for these guiding structures have been reduced considerably.This work was supported in part by the National Natural Science Foundation of China under Grant 11535008 and in part by the Fundamental Research Funds for Shandong University under Grant 2014JC002. The work of J. R. V. de Aldana was supported by Junta de Castilla y León (UIC016 and SA046U16). The work of S. Zhou was supported by the Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF-VH-NG-713)

Strength of the EpE_{\text{p}}=1.842 MeV resonance in the 40^{40}Ca(p,γ\gamma)41^{41}Sc reaction revisited

The strength of the $E_{\rm p} = 1.842$ MeV resonance in the $^{40}$Ca(p,$\gamma$)$^{41}$Sc reaction is determined with two different methods: First, by an absolute strength measurement using calcium hydroxide targets, and second, relative to the well-determined strength of the resonance triplet at $E_\alpha$ = 4.5 MeV in the $^{40}$Ca($\alpha$,$\gamma$)$^{44}$Ti reaction. The present new value of $\omega\gamma=(0.192\pm0.017)$ eV is 37% (equivalent to $3.5\sigma$) higher than the evaluated literature value. In addition, the ratio of the strengths of the 1.842 MeV $^{40}$Ca(p,$\gamma$)$^{41}$Sc and 4.5 MeV $^{40}$Ca($\alpha$,$\gamma$)$^{44}$Ti resonances has been determined to be $0.0229\pm0.0018$. The newly corrected strength of the 1.842-MeV resonance can be used in the future as a normalization point for experiments with calcium targets.Comment: Submitted to Phys. Rev.

Optical ridge waveguides in 4H-SiC single crystal produced by combination of carbon ion irradiation and femtosecond laser ablation

Optical ridge waveguides were fabricated in 4H-SiC single crystal by combination of 15 MeV C5+ ion irradiation and femtosecond laser ablation. The near-field modal intensity distributions exhibit the well-confined light propagation in the waveguides. A propagation loss as low as 5.1 dB/cm has been achieved at 632.8 nm for the ridge waveguide. The investigation of confocal micro-Raman spectra suggests partial transition of 4H-SiC to 6H-SiC in the irradiated regionThe work was carried out under the support by National Natural Science Foundation of China (No. U1332121) and the 973 Project (No. 2010CB832906) of China. The work was also supported by the Helmholz-Gemeinschaft Deutscher Forschungszentren (HGF-VH-NG-713) and Junta de Castilla y León (Project SA086A12-2)

Strengths of the resonances at 436, 479, 639, 661, and 1279 keV in the 22^{22}Ne(p,γ\gamma)23^{23}Na reaction

The $^{22}$Ne(p,$\gamma$)$^{23}$Na reaction is included in the neon-sodium cycle of hydrogen burning. A number of narrow resonances in the Gamow window dominates the thermonuclear reaction rate. Several resonance strengths are only poorly known. As a result, the $^{22}$Ne(p,$\gamma$)$^{23}$Na thermonuclear reaction rate is the most uncertain rate of the cycle. Here, a new experimental study of the strengths of the resonances at 436, 479, 639, 661, and 1279 keV proton beam energy is reported. The data have been obtained using a tantalum target implanted with $^{22}$Ne. The strengths $\omega\gamma$ of the resonances at 436, 639, and 661 keV have been determined with a relative approach, using the 479 and 1279 keV resonances for normalization. Subsequently, the ratio of resonance strengths of the 479 and 1279 keV resonances was determined, improving the precision of these two standards. The new data are consistent with, but more precise than, the literature with the exception of the resonance at 661 keV, which is found to be less intense by one order of magnitude. In addition, improved branching ratios have been determined for the gamma decay of the resonances at 436, 479, and 639 keV.Comment: Final version, now using the Kelly et al. (2015) data [15] for normalization; 10 pages, 7 figures, 3 table

Towards diluted magnetism in TaAs

Magnetism in Weyl semimetals is desired to investigate the interaction between the magnetic moments and Weyl fermions, e.g. to explore anomalous quantum Hall phenomena. Here we demonstrate that proton irradiation is an effective tool to induce ferromagnetism in the Weyl semimetal TaAs. The intrinsic magnetism is observed with a transition temperature above room temperature. The magnetic moments from d states are found to be localized around Ta atoms. Further, the first-principles calculations indicate that the d states localized on the nearest-neighbor Ta atoms of As vacancy sites are responsible for the observed magnetic moments and the long-ranged magnetic order. The results show the feasibility of inducing ferromagnetism in Weyl semimetals so that they may facilitate the applications of this material in spintronics.Comment: 20 pages, 6 figure