Fracture-strength Weibull plots. The single-crystal plot is based on test data recorded in Ref. 12; the broken line refers to fusion-cast as in Ref. 15. Note that the fusion-cast “fit” holds for test bars measuring .
Total absorptance of fusion-cast test rods as a function of path length, at laser wavelengths of 2.7 (filled squares) and (open squares). The straight lines are least-squares fits. The bulk absorption is seen to be wavelength independent; surface absorptance reflects the impact of adsorbed water.
Cumulative failure probability of (111)-oriented and fusion-cast model windows as a function of the applied biaxial stress. The stress is assumed uniform over the entire aperture. Relevant Weibull statistical parameters are listed in Table II.
Pressure-induced optical path differences (OPDs), measured in “waves,” as a function of radial position. The calculation assumes a diameter of , a thickness of , and a differential pressure of . Relevant wavelengths are 1.15 and .
Radial and azimuthal phase-shift dependences on radial position, for model windows as specified in Sec. III. The transmitted peak fluence is set equal to . (a) Laser wavelength ; (b) Laser wavelength .
Focal intensity degradation as a function of the transmitted peak fluence, for the two model windows described in Sec. III. The figure illustrates the cases of a laser wavelength of and a laser wavelength of . Note that this evaluation ignores the impact of stress-related limitations on allowable fluences.
Peak tensile stress as a function of beam-exposure time for (a) the (111)-oriented model window and (b) the fusion-cast model window. The symbol refers to the peak irradiance level. The allowable stresses are as discussed in Sec. VI A.
Peak compressive stress as a function of the beam-exposure time for (a) the (111)-oriented model window and (b) the fusion-cast model window. The symbol refers to the peak irradiance level. The yield strengths are as listed in Table II.
Allowable peak fluences as a function of the peak intensity for model windows as specified in Sec. III. The plot is based on allowable beam-exposure times obtained from Figs. 7 and 8. Note that the allowable fluences fall off rapidly at peak intensities that exceed , owing to surface-compression induced yieding.
Illustrates the performance of (111)-oriented and fusion-cast windows in terms of (a) focal-point irradiances and (b) focal-point fluences, at a distance of . The optical train—but for the output window—is assumed to be aberration-free; the output windows are as specified in Sec. III. Taking the truncation into account, the transmitted beam power amounts to 9.2 and for and windows, respectively.
List of symbols (see also Table II).
Key properties of (111)-oriented and fusion-cast at room temperature.
Key optical-distortion related results for model windows as specified in Sec. III; all relevant numbers are based on property values listed in Table II.
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