Abstract: The high-purity alkaline earth halide crystals, especially CaF2, BaF2 or MgF2 crystals, have a diffuse scatter distribution function value of less than 7×10?7, an RMS uniformity of refractive index of less than 15×10?8 after subtraction of Zernike coefficients and an RMS value of birefringence in the (111) direction of less than 0.2 nm/cm. Preferably the crystals exhibit a loss coefficient of less than 5×10?4 cm?1 after irradiation with 10×109 laser pulses with an energy density of 10 mJ/cm2 at a wavelength of 193 nm. Also they have RMS birefringence in the (100) direction or the (111) direction that is less than 0.35 nm/cm.

Abstract: A method for producing high-purity, large-volume monocrystals that are especially radiation-resistant and have low intrinsic birefringence. From a melt of crystalline raw material, with controlled cooling and solidification, a crystal is generated. As the crystalline raw material, shards and/or waste from already-grown crystals is used, and the re-used raw material 1) upon visual observation in daylight has no color; and 2) upon illumination with a white-light lamp in a darkroom a) has no or at maximum a just barely perceivable reddish and/or bluish fluorescence; and b) has no or at maximum a just barely perceivable diffuse scattering; and c) has no or only slight discrete scattering of at maximum two visually perceivable scattering centers per dm3. In this way, crystals can be obtained which after tempering have a BSDF value of <7×10?7, an RMS homogeneity after the subtraction of 36 Zernike coefficients of <15×10?8, an SDR-RMS value in the 111 direction of <0.2 nm/cm.

Abstract: Single crystals with low scattering, small refractive index differences and few small angle grain boundaries have a bi-directional scattering distribution function value (BSDF) of less than 1.5*10?6 or 5*10?7.

Abstract: The method provides CaF2 single crystals with low scattering, small refractive index differences and few small angle grain boundaries, which can be tempered at elevated temperatures. In the method a CaF2 starting material is heat-treated for at least five hours at temperatures between 1000° C. and 1250° C. and then vaporized at a temperature of at least 1100° C. in a vacuum of at most 5*10?4 mbar to form a vapor. The vapor is condensed at a temperature between 500° C. to 1280° C. to form a condensate. Then a melt formed from the condensate is cooled in a controlled manner to obtain the single crystal, which is subsequently tempered. The method is preferably performed with a CaF2 starting material including waste material and cuttings from previously used melts.

Abstract: The method provides CaF2 single crystals with low scattering, small refractive index differences and few small angle grain boundaries, which can be tempered at elevated temperatures. In the method a CaF2 starting material is heat-treated for at least five hours at temperatures between 1000° C. and 1250° C. and then sublimed at a sublimation temperature of at least 1100° C. in a vacuum of at most 5*10?4 mbar to form a vapor. The vapor is condensed at a condensation temperature of at least 500° C., which is at least 20° C. below the sublimitation temperature, to form a condensate. Then a melt formed from the condensate is cooled in a controlled manner to obtain the single crystal, which is subsequently tempered. The method is preferably performed with a CaF2 starting material including waste material and cuttings from previously used melts.

Abstract: The method for producing single crystals includes drying crystal raw material by removing water, reaction of impurities with a scavenger, preferably a metal halide, and homogenizing the melt. The method is performed with the raw material in a melt vessel with a variable-sized through-going opening, in which drying occurs at 100° C. to 600° C. for at least 20 hours with a geometric conductance value for the through-going opening of 2.00 to 30.00 mm2; the reacting occurs at 600° C. to 1200° C. for at least nine hours with a geometric conductance value of 0.0020 to 0.300 mm2 and the homogenizing occurs at above 1400° C. for at least six hours with a geometric conductance value of 0.25 to 1.1 mm2. Alternatively the geometric conductance value is the same during drying, reacting and homogenizing and takes a value between 0.25 and 1 mm2.

Abstract: A method for producing high-purity, large-volume monocrystals that are especially radiation-resistant and have low intrinsic birefringence. From a melt of crystalline raw material, with controlled cooling and solidification, a crystal is generated. As the crystalline raw material, shards and/or waste from already-grown crystals is used, and the re-used raw material 1) upon visual observation in daylight has no color; and 2) upon illumination with a white-light lamp in a darkroom a) has no or at maximum a just barely perceivable reddish and/or bluish fluorescence; and b) has no or at maximum a just barely perceivable diffuse scattering; and c) has no or only slight discrete scattering of at maximum two visually perceivable scattering centers per dm3. In this way, crystals can be obtained which after tempering have a BSDF value of <7×10?7, an RMS homogeneity after the subtraction of 36 Zernike coefficients of <15×10?8, an SDR-RMS value in the 111 direction of <0.2 nm/cm.

Abstract: The method provides CaF2 single crystals with low scattering, small refractive index differences and few small angle grain boundaries, which can be tempered at elevated temperatures. In the method a CaF2 starting material is heat-treated for at least five hours at temperatures between 1000° C. and 1250° C. and then vaporized at a temperature of at least 1100° C. in a vacuum of at most 5*10?4 mbar to form a vapor. The vapor is condensed at a temperature between 500° C. to 1280° C. to form a condensate. Then a melt formed from the condensate is cooled in a controlled manner to obtain the single crystal, which is subsequently tempered. The method is preferably performed with a CaF2 starting material including waste material and cuttings from previously used melts.

Abstract: The method for producing single crystals includes drying crystal raw material by removing water, reaction of impurities with a scavenger, preferably a metal halide, and homogenizing the melt. The method is performed with the raw material in a melt vessel with a variable-sized through-going opening, in which drying occurs at 100° C. to 600° C. for at least 20 hours with a geometric conductance value for the through-going opening of 2.00 to 30.00 mm2; the reacting occurs at 600° C. to 1200° C. for at least nine hours with a geometric conductance value of 0.0020 to 0.300 mm2 and the homogenizing occurs at above 1400° C. for at least six hours with a geometric conductance value of 0.25 to 1.1 mm2. Alternatively the geometric conductance value is the same during drying, reacting and homogenizing and takes a value between 0.25 and 1 mm2.

Abstract: A method of making a fracture-resistant large-size calcium fluoride single crystal is described, which is suitable for an optical component for radiation in the far UV range. The calcium fluoride raw material for the single crystal is first melted and subsequently solidified by cooling the melt to form a single crystal. However the calcium fluoride raw material is doped with from 1 to 250, preferably 1 to 100, ppm of strontium, preferably added as strontium fluoride, and contains from 1 to 10 ppm of sodium as well as up to 100 ppm of other impurities.

Abstract: The method for determining radiation stability of a crystal to radiation of a working wavelength to be employed in a subsequent application includes taking a first absorption spectrum (A) of a cleaved piece of the crystal with a given thickness (D) over a predetermined wavelength range from a first wavelength (&lgr;1) to a second wavelength (&lgr;2) by means of a spectrophotometer. Then the cleaved piece of the crystal is irradiated with an energetic radiation source so as to form all theoretically possible color centers (saturation). After the irradiating a second absorption spectrum (B) of the cleaved piece of crystal is taken over the same predetermined wavelength range. Then a surface integral of a difference spectrum of the first absorption spectrum and the second absorption spectrum over the predetermined wavelength range is formed and divided by the thickness (D) to obtain a scaled surface integral value.

Abstract: A method of making a fracture-resistant large-size calcium fluoride single crystal is described, which is suitable for an optical component for radiation in the far UV range. The calcium fluoride raw material for the single crystal is first melted and subsequently solidified by cooling the melt to form a single crystal. However the calcium fluoride raw material is doped with from 1 to 250, preferably 1 to 100, ppm of strontium, preferably added as strontium fluoride, and contains from 1 to 10 ppm of sodium as well as up to 100 ppm of other impurities.

Abstract: The method for determining radiation stability of a crystal to radiation of a working wavelength to be employed in a subsequent application includes taking a first absorption spectrum (A) of a cleaved piece of the crystal with a given thickness (D) over a predetermined wavelength range from a first wavelength (&lgr;1) to a second wavelength (&lgr;2) by means of a spectrophotometer. Then the cleaved piece of the crystal is irradiated with an energetic radiation source so as to form all theoretically possible color centers (saturation). After the irradiating a second absorption spectrum (B) of the cleaved piece of crystal is taken over the same predetermined wavelength range. Then a surface integral of a difference spectrum of the first absorption spectrum and the second absorption spectrum over the predetermined wavelength range is formed and divided by the thickness (D) to obtain a scaled surface integral value.