Generation of vacuum-ultraviolet light by an optically contacted,prism-coupled KBe2BO3F2 crystal

We have demonstrated the second harmonic of a frequency-tripled Nd:YVO4 laser with 2.5-mW quasi-cw output by using an optically contacted, prism-coupled KBe2BO3F2 crystal. We also achieved the second harmonic with a frequency-doubled single-mode Ti:sapphire laser at 172.5 nm and sum-frequency mixing with a dual-wavelength Ti:sapphire laser at 163.3 nm. These wavelengths are to our knowledge the shortest obtained by use of nonlinear crystals for second-harmonic generation and sum-frequency mixing, respectively.     

High-power sixth-harmonic generation of an Nd:YAG laser with KBe2BO3F2 prism-coupled devices

High-power sixth harmonic generation from an Nd:YAG laser (10 ns, 10 kHz) has been achieved with a KBe₂BO₃F₂ (KBBF) prism-coupled device (PCD) containing a 1.95 mm thick KBBF crystal. The highest output power reached 120.5 mW at 177.3 nm, and the highest conversion efficiency from 354.7 to 177.3 nm was 1.82%. Moreover, stable sixth harmonic output with an average power of 22.2 mW was produced by another KBBF-PCD, in which the thickness of the KBBF crystal was 1.51 mm. The highest and stable sixth harmonic output powers are improved by about three and six times compared with the previously published results, respectively.     

Second-harmonic generation from a KBe(2) BO(3)F(2) crystal in the deep ultraviolet

By use of KBe(2)BO(3)F(2) (KBBF) crystal with a size of 10 mmx10 mm x1.2 mm and a special prism-coupling technique (PCT), fourth-harmonic generation of Ti:sapphire laser systems from 200 to 179.4 nm has been achieved. Moreover, with a Ti:sapphire laser with a 50-fs pulse duration and a 1-kHz repetition rate, conversion efficiency as high as 13% from 400 to 200 nm without any surface-loss correction has also been obtained. The data show that with the PCT a KBBF crystal can produce deep-UV coherent light with measurable power output.     

Investigation of third-order optical nonlinearity in KBe2BO3F2 crystal by Z-scan

The third-order optical nonlinearity of deep-ultraviolet (DUV) nonlinear optical (NLO) crystal KBe₂BO₃F₂ (KBBF) was investigated using single-beam Z-scan technique for the first time. The Z-scans were performed on a c-cut KBBF crystal and a KBBF prism-coupling device (PCD) with picosecond pulses at 355?nm. No two-photon absorption was observed in the experiment. The measured nonlinear refraction index n ₂ showed positive signs, indicating self-focusing Kerr effects. The n ₂ values were estimated to be (1.75±0.35)×10^?15?cm²/W with the c-cut sample and (1.85±0.37)×10^?15?cm²/W with the PCD, corresponding to the third-order nonlinear optical susceptibilities $\chi_{\mathrm{eff}}^{(3)}$ of (0.99±0.20)×10^?13?esu and (0.94±0.19)×10^?13?esu, respectively. The results are expected to promote the investigation of frequency conversion processes with ultra-short laser in KBBF crystal.     

KBe2BO3F2飞秒光参量放大中的群速匹配

提出了KBe2BO3F2 (KBBF)飞秒光参量放大中三波群速完全匹配的方法.对于Ⅰ类相位匹配方式采用非共线结构及倾斜抽运光脉冲波面,对于Ⅱ类相位匹配方式采用共线结构同时倾斜抽运光和信号光脉冲波面,可实现参量带宽最大时三波群速的完全匹配,从而获得更高增益,更窄脉宽的参量光.     

Ab initio studies on the optical effects in the deep ultraviolet nonlinear optical crystals of the KBe(2)BO(3)F(2) family

Electronic structures of the deep ultraviolet nonlinear optical crystals of the KBe(2)BO(3)F(2) (KBBF) family, including KBBF, RbBe(2)BO(3)F(2) and CsBe(2)BO(3)F(2), have been investigated based on a plane-wave pseudopotential method. Their linear and nonlinear optical coefficients are also calculated, and are in good agreement with the experimental results. A real-space atom-cutting method is adopted to analyze the respective contributions of the alkali metal cations and anionic groups to optical response. The results show that the contributions of anionic groups to the nonlinear optical anisotropic responses are dominant, but the influence of the A-site alkali metal cations becomes slightly more pronounced with the increase of their radius. Moreover, the birefringence difference among these crystals strongly depends on the volume effect, i.e.,?the spatial density of the (BO(3))(3-) anionic groups.     

The (2H-d)-reactions below 200 keV

The²H(d, n)- and²H(d, p)-reactions are studied for deuteron energies below 200 keV. It is shown that theR-matrix approach of Konopinski and Teller, which is very sensitive to the channel radius used, can be approximated in a way that the dependence on the channel radius does not appear explicitly. This approach appears to be formally equivalent to a kind of “direct approach” of Boersma. This equivalence answers the question why a direct approach to these reactions works at all at low energies. Each reaction is described by three parameters which are determined in a fit to the up to now available data.     

Magnetization plateaus of SrCu(2)(BO(3))(2) from a Chern-Simons theory

The antiferromagnetic Heisenberg model on the frustrated Shastry-Sutherland lattice is studied by a mapping onto spinless fermions carrying one quantum of statistical flux. Using a mean-field approximation these fermions populate the bands of a generalized Hofstadter problem. Their filling leads to the magnetization curve. For SrCu(2)(BO(3))(2) we reproduce plateaus at 1/3 and 1/4 of the saturation moment and predict a new one at 1/2. Gaussian fluctuations of the gauge field are shown to be massive at these plateau values.     

Luminescence characteristics of Dy3+ activated Na 2Sr 2Mg (BO 3)2F 2: Dy 3+ phosphor

In this paper, we have reported a new Na ₂Sr ₂Mg (BO ₃)₂F ₂:Dy ³⁺ thermoluminescence (TL) phosphor prepared via the wet chemical method. Prepared phosphor was characterized by X-ray powder diffraction, photoluminescence (PL), TL and scanning electronmicroscopy techniques. The scanning electronmicroscopic image of Na ₂Sr ₂Mg (BO ₃)₂F ₂:Dy ³⁺ phosphor confirms the micron size of particles. Under the PL study, the characteristic emission spectrum of Dy ³⁺ corresponding to ⁴F _9/2→⁶H _15/2 (481 nm) and ⁴F _9/2→⁶H _13/2 (576 nm) transitions was observed. The TL property of the as prepared phosphor was also found to be good. TL intensity of Na ₂Sr₂Mg(BO ₃)F ₂:Dy ³⁺ phosphors at 0.99 kGy exposure of γ-irradiations was compared with standard CaSO ₄:Dy phosphor. It was seen that TL intensity of Na ₂Sr ₂Mg (BO ₃)₂F ₂: Dy ³⁺ phosphors is 1.1 times less compared with the standard CaSO ₄:Dy TL dosimeter phosphor. The kinetic parameters are also discussed in detail. The values of activation energy E (eV) and frequency factor S (s ^?1) were found to be 0.57 eV and 1.25×10⁶ s^?1, respectively.     

157-nm coherent light source as an inspection tool for F(2) laser lithography

We have developed a 157-nm coherent light source by two-photon resonant four-wave mixing in Xe, with two tunable single-mode 1-kHz Ti:sapphire laser systems at 768 and 681 nm. This light source has been developed to determine the instrumental function of a vacuum ultraviolet spectrometer and to evaluate optical designs for ultra-line-narrowed F(2) laser lithography. The spectral linewidth of the source was less than 0.008 pm (FWHM), with an average power of 0.6 mW.     

Acousto-optic Q-switched self-frequency-doubling Er:Yb:YAl3(BO3)4 laser at 800 nm

Actively Q-switched self-frequency-doubling laser at 800 nm was first reported in an Er:Yb:YAl3(BO3)4 crystal by using an acousto-optical modulator. At incident pump power of 16 W and pulse repetition frequency of 1 kHz, 1600 nm fundamental pulse laser with energy of 130 μJ and width of 170 ns, and self-frequency-doubling 800 nm pulse laser with energy of 20 μJ and width of 96 ns were respectively achieved in a hemispherical resonator end-pumped by a 970 nm laser diode. Pulse characteristics of fundamental and self-frequency-doubling lasers at different pulse repetition frequencies were also investigated.     

Short-pulse generation from a resonantly pumped NdAl3(BO3)4 microchip laser

We report on continuous-wave and subnanosecond passively Q-switched laser oscillation from a NdAl3(BO3)4 microchip laser operating at 1.06 microm. Efficient and stable laser operation is possible only when resonant pumping (4I9/2-->4F3/2 at 882 nm) is used instead of the traditional 4I9/2-->4F5/2 (808 nm) pumping. The improvement in laser performance is caused by a strong reduction in the pump-induced thermal loading, which is achieved by pumping directly into the emitting level.     

Ultraviolet-Cathodoluminescent 330 nm light source from a 2-inch wide CNT electron-beam emission under DC electric field

We report a 2-inch wide-area AlGaN-based ultraviolet (UV) – cathodoluminescence (CL) light source emission using electron beam (EB) pumped source under DC electric field from an AlGaN/GaN multi-quantum-well grown on a sapphire substrate. The EB-pumping is achieved by wide-area carbon nanotubes (CNT) based field emitters and is arranged via a metal mesh, thereby acting as a gate to pump the electron flow. We have carried out UV–CL measurements with a turn-on field emission in the anode voltage ranging between 5 kV and 9 kV at anode current up to 1 mA. The best results are obtained at the low consumption energy of 7 W (anode current 1 mA; anode voltage 7 kV). The 330 nm UV–CL emission shows an output power of ~225 mW, with an as-calculated power efficiency of ~3.6%. The CL measurements show (5–8) % defect luminescence in the visible region.     

1180 nm Raman laser operation of end-pumping Nd:GdAl3(BO3)4/SrWO4 crystal

We present an end-pumped continuous-wave Raman laser at 1180 nm with a 60 mm long pure crystal SrWO₄ and an Nd:GdAl₃(BO₃)₄ crystal. The highest output power Raman laser at 1180 nm is 15.5 mW corresponding to the pump power of 1.75 W. Results indicate that the intense self-doubling frequency effect of GdAl₃(BO₃)₄ reduces the 1180 nm Raman laser output.     

BaZr(BO3)2:Eu的合成及发光性能研究

用硝酸盐热分解法成功制备了BaZr(BO3)2:Eu(Eu3+的掺杂量为摩尔分数5%)荧光材料,并研究了其在254及147 nm光束激发下的发光特性.254 nm光束激发下的发射主峰位于612 nm处,归属于Eu3+的5D0-7F2的电偶极跃迁,但在147 nm光束激发下的发射主峰位于592 nm处,归属于Eu3+的5D0-7F1的磁偶极跃迁.通过激发光谱分析,上述现象归因于在紫外激发下占据非对称格位Ba2+的Eu3+被优先激发,而在真空紫外激发下占据对称格位Zr4+的Eu3+被优先激发.结果表明BaZr(BO3)2:Eu并不适合作为等离子平板显示器用红色发光材料.     

Generation of 90-fs pulses from a mode-locked diode-pumped Yb(3+):Ca(4)GdO(BO(3))(3) laser

A diode-pumped Yb>(3+):Ca(4)GdO(BO>(3))(3) (Yb:GdCOB) laser generating 90-fs pulses at a center wavelength of 1045 nm is demonstrated. This is, to our knowledge, the shortest pulse duration obtained from an ytterbium laser with a crystalline host. This laser is mode locked with a high-finesse semiconductor saturable-absorber mirror and emits 40 mW of average power at a repetition rate of 100 MHz.