Author Affiliations
1Department of Projection Optics, Academy of Opto-Electronics, Chinese Academy of Sciences, Beijing 100094, China2Beijing Excimer Laser Technology and Engineering Center, Beijing 100094, China3University of Chinese Academy of Sciences, Beijing 100049, Chinashow less
Fig. 1. Structural diagram of CaF2 crystal
Fig. 2. CaF2 crystal. (a) Transmission spectrum; (b) relationship between refractive index and wavelength[4]
Fig. 3. SEM images of laser-damaged CaF2. (a) Irradiated by ten ArF laser pulses (6.7 J/cm2); (b) irradiated by six ArF laser pulses (7.8 J/cm2)
Fig. 4. SEM images of damage topographies of CaF2 (111) surfaces radiated by laser with different fluences. (a) Conventional standard polish,27.6 J/cm2; (b) diamond turned surface,30 J/cm2; (c) chemo-mechanically polished surface, 57.7 J/cm2; (d) terrace area of cleaved surface, 46 J/cm219
Fig. 5. Time-resolved photoluminescence spectra of CaF2 specimen under excitation with ArF excimer laser pulse. (a) Excimer grade A; (b) excimer grade B; (c) UV grade[22]
Fig. 6. ArF-induced absorption spectra of sodium-doped CaF2 crystal (sample A) and typical pure-CaF2 crystal (sample B)[25]
Fig. 7. Laser induced damage thresholds under excitation of ArF excimer[28]
Fig. 8. Relationship between laser damage threshold and angle between laser polarization plane and crystal axis orientation of <111> axis[29]
Fig. 9. Laser-induced damage probability as a function of fluence for F-SiO2 protective coating and F-SiO2 protected AR coating[39]
Parameter | Value | Parameter | Value |
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Crystal density /(g·cm-3) | 3.180 | Melting point /℃ | 1423 | Melt density /(g·cm-3) | 2.594 | Boiling point /℃ | 2500 | Young's modulus /GPa | 89.80 | Thermal emissivity | 0.8 | Shear modulus /GPa | 33.77 | Expansion coefficient of heat /(10-6 K-1) | 18 | Volume modulus /GPa | 82.71 | Crystal thermal conductivity /(W·m-1·K-1) | 9.71 | Poisson's coefficient | 0.28 | Crystal heat transfer coefficient /(W·m-2·K-1) | 5 | Moh hardness | 4 | Melt heat transfer coefficient /(W·m-2·K-1) | 10 | Dielectric constant (1 MHz) | 6.76 | Specific heat (273 K) /(J·g-1·K-1) | 0.88 |
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Table 1. Physicochemical properties of CaF29,12
Sample | Laser induced damagethreshold @560 fs | Laser induced damagethreshold @25 fs |
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CaF2 | 1.8 | 16.1 | MgF2 | 1.7 | 16.2 | LiF2 | 0.365 | 9.4 | BaF2 | 0.341 | 9.4 | Suprasil | 1.99 | 6.85 |
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Table 2. Laser induced damage thresholds of ultraviolet transmitting crystals and fused silica