Growth of high-quality transparent SrB<sub>4</sub>O<sub>7</sub> single crystals with high degradation resistance for DUV laser application

Tanaka, Yasunori; Shikata, Keita; Murai, Ryosuke; Takahashi, Yoshinori; Imanishi, Masayuki; Sugita, Tsuyoshi; Mori, Yusuke; Yoshimura, Masashi

doi:10.7567/apex.11.125501

Cited by 9 publications

(11 citation statements)

References 30 publications

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“…Strontium tetraborate (SrB 4 O 7 , SBO) has an orthorhombic structure and belongs to the space group Pmn 2 1 ( a = 4.4273 Å, b = 10.714 Å, and c = 4.2359 Å). , SBO crystals show high nonlinearity − and are transparent down to the deepest ultraviolet wavelengths (125 nm). − Hence, SBO continues to receive much attention as a solid-state ultraviolet laser crystal for a wide variety of applications that include semiconductor photolithography, micromachining, photochemical synthesis, laser spectroscopy, and photoemission spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Effects of the Application of Electric Fields on the Growth of SrB₄O₇ Crystals by the Micro-Pulling-Down Method

Inaba

Ishibashi

Asakawa

et al. 2020

Crystal Growth & Design

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SrB 4 O 7 (SBO) has received much attention as a solid-state ultraviolet laser crystal for a wide variety of applications such as micromachining and spectroscopy. Here we demonstrate the effects of electric fields E on the growth of SBO crystals along the b axis by the μ-pulling-down method to fabricate SBO with periodic twins, which increases the conversion light intensity. During the growth, the direction of electric fields was alternated for 30 min periods. The crystal fibers were evaluated by polarized optical microscopy, X-ray diffraction, and transmission electron microscopy. Without an external voltage, single SBO crystals grew. In contrast, at E ≥ 400 V/cm needles of SrB 2 O 4 appeared inside SBO fibers. At E ≥ 1000 V/cm, new domains of SBO grew from the seed crystals, and interestingly, growth twins were formed perpendicular to growth fronts. Thus, we found that the growth of SBO by the μ-PD method via alternating the application of opposing electric fields exhibits two mechanisms. In contrast, when the electrodes in melt and growth fronts switched to + and −, respectively, growth fronts changed from concave into convex shapes, irrespective of E. We could explain the relation between the two mechanisms and the inversion of surface shapes, using the convection.

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Section: Introductionmentioning

confidence: 99%

Effects of the Application of Electric Fields on the Growth of SrB₄O₇ Crystals by the Micro-Pulling-Down Method

Inaba

Ishibashi

Asakawa

et al. 2020

Crystal Growth & Design

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“…22 SBO also exhibited good degradation resistance at the deep ultraviolet wavelength of 266 nm. 18 Interestingly, it was recently reported that partially twinned SBO crystals were obtained by the Czochralski (CZ) method and showed quasi-phase matching. As a result, amplifying wavelength-conversion light intensity was detected.…”

Section: Introductionmentioning

confidence: 99%

“…Borate crystals such as β-BaB 2 O 4 (BBO), − CsLiB 6 O 10 (CLBO), − and Li 2 B 4 O 7 (LBO) − are utilized as nonlinear crystals in the ultraviolet region. In particular, SrB 4 O 7 (SBO) is a promising material as wavelength conversion crystals which are transparent down to the deepest ultraviolet wavelengths (125 nm). − …”

Section: Introductionmentioning

confidence: 99%

“…SBO has an orthorhombic structure and belongs to the space group Pmn 2 1 , with a = 10.714 Å, b = 4.4273 Å, and c = 4.2359 Å. , It has been reported to be a highly nonlinear crystal. − ,, Our previous study succeeded in generating wavelength conversion of femtosecond second-harmonic-generation pulses to 125 nm using SBO crystals . SBO also exhibited good degradation resistance at the deep ultraviolet wavelength of 266 nm . Interestingly, it was recently reported that partially twinned SBO crystals were obtained by the Czochralski (CZ) method and showed quasi-phase matching.…”

Section: Introductionmentioning

confidence: 99%

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Growth of SrB₄O₇ Crystal Fibers with Near-Stoichiometric Composition by the Micro-Pulling-Down Method

Asakawa

Machida

Inaba

et al. 2019

Crystal Growth & Design

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SrB 4 O 7 (SBO) has recently received much attention as a wavelength-conversion material which can operate into the deepest ultraviolet wavelengths (125 nm). The utilization of SBO for semiconductor lithography and laser ablation requires fully transparent crystals. Here, we show the growth of SBO crystal fibers with near-stoichiometric composition by the μ-pulling-down method. SrB 2x O 3x+1 ceramics sintered with various values of x were evaluated by X-ray diffraction (XRD). The melting point of the SBO ceramics was measured by differential scanning calorimetry (DSC) as 1017 °C, and the heat of fusion was 63.3 J/g. Furthermore, we observed SBO crystal fibers grown with various x values by optical microscopy. As a result, even when the deviation from stoichiometric composition was ± −0.1 mol % SrO (x = 2 ± 0.004), SrB 2 O 4 /SrB 6 O 10 appeared. Also, DSC curves of SBO ceramics exhibited only one melting peak. These results demonstrate that SBO shows no solid-solution width and that the stoichiometric composition is equal to the congruent composition. Furthermore, we succeeded in obtaining transparent SBO crystal fibers by growth with a stoichiometric composition. In contrast, since growth ridges including SrB 2 O 4 /SrB 6 O 10 were formed on surfaces of the SBO single crystals, SBO crystal fibers grown with nonstoichiometric composition were opaque. We could explain the formation of growth ridges via compositional supercooling on rims.

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“…SrB 4 O 7 (SBO) belongs to an orthorhombic structure with the space group of Pmn2 1 (a = 4.4273 Å, b = 10.714 Å, c = 4.2359 Å) [1,2]. SBO crystals also show high nonlinearity [3][4][5][6][7] and are transparent down to the deepest ultraviolet wavelength (125 nm) [4][5][6][7][8][9]. Hence, SBO receives much attention as solid-state ultraviolet lasers for semiconductor photolithography, micro-machining, photochemical synthesis, laser spectroscopy, and photoemission spectroscopy.…”

Section: Introductionmentioning

confidence: 99%

Growth of SrB4O7 Crystal Fibers along the c-Axis by Micro-Pulling-Down Method

2021

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SrB4O7 (SBO) receives much attention as solid-state ultraviolet lasers for micro-machining, photochemical synthesis, and laser spectroscopy. For the application of SBO, the SBO crystals require the control of twinning to amplify the conversion light. We also expected that the inhibitation of the SrB2O4 appearance was essential. Here, we show the growth of SBO crystals along the c-axis through the micro-pulling-down method while alternating the application of electric fields (E). Without the application, single crystals were grown. At E ≧ 400 V/cm no needle domains of SrB2O4 inside SBO crystals existed; however, composition planes were formed and twin boundaries did not appear. In contrast, the inversion of surface morphology emerged, and the convex size was especially large at 1000 V/cm. These results demonstrate that convection is generated perpendicular to the growth front by alternating the application of electric fields. This surface morphological change contradicts the conventional concept of growth through the micro-pulling-down method. The distance from seed crystals vs. grain density plot also showed that the density did not decrease with a sufficient slope. Consequently, we concluded that the selection of the c-axis as growth faces is not fruitful to fabricate twins, and the selection of the growth condition, under which geometrical selection strongly affects, is the key.

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Growth of high-quality transparent SrB₄O₇ single crystals with high degradation resistance for DUV laser application

Cited by 9 publications

References 30 publications

Effects of the Application of Electric Fields on the Growth of SrB₄O₇ Crystals by the Micro-Pulling-Down Method

Effects of the Application of Electric Fields on the Growth of SrB₄O₇ Crystals by the Micro-Pulling-Down Method

Growth of SrB₄O₇ Crystal Fibers with Near-Stoichiometric Composition by the Micro-Pulling-Down Method

Growth of SrB4O7 Crystal Fibers along the c-Axis by Micro-Pulling-Down Method

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Growth of high-quality transparent SrB4O7 single crystals with high degradation resistance for DUV laser application

Cited by 9 publications

References 30 publications

Effects of the Application of Electric Fields on the Growth of SrB4O7 Crystals by the Micro-Pulling-Down Method

Effects of the Application of Electric Fields on the Growth of SrB4O7 Crystals by the Micro-Pulling-Down Method

Growth of SrB4O7 Crystal Fibers with Near-Stoichiometric Composition by the Micro-Pulling-Down Method

Growth of SrB4O7 Crystal Fibers along the c-Axis by Micro-Pulling-Down Method

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Growth of high-quality transparent SrB₄O₇ single crystals with high degradation resistance for DUV laser application

Effects of the Application of Electric Fields on the Growth of SrB₄O₇ Crystals by the Micro-Pulling-Down Method

Effects of the Application of Electric Fields on the Growth of SrB₄O₇ Crystals by the Micro-Pulling-Down Method

Growth of SrB₄O₇ Crystal Fibers with Near-Stoichiometric Composition by the Micro-Pulling-Down Method