Hellma German synthesized calcium fluoride (CaF ₂) optical crystal

Hellma German synthesized calcium fluoride (CaF ₂) optical crystal

1、 Basic physical and chemical properties

• chemical formula: CaF ₂ (calcium fluoride)

• crystal structure: Cubic crystal system, (111) cleavage plane

• density：3.18 g/cm³

• melting point：1418 °C

• thermal conductivity：9.71 W/(m·K) @20 °C

• Coefficient of thermal expansion (CTE)：18.9×10 ⁻⁶ / K @20 °C

• Solubility (water, 20 ° C): 0.016 g/L (extremely insoluble)

2、 Optical Performance (Core)

• Transmission band：130 nm (deep ultraviolet)~9 μ m (mid infrared)Covering the entire VUV/DUV/visible/infrared spectrum.

• Internal transmittance (10mm thick)：

• UV（193/248 nm）：>99.0%

• VIS：>92%

• IR（3~5 μm）：>90%

• Refractive index（ nd@587.6 nm）：1.43384(Low refractive index, minimal optical path distortion)

• Abbe number (ν d)：95.23(Extremely low dispersion, excellent color correction)

• Uniformity of refractive index (@ 633 nm)：≤ 0.5 ppm/3-20 ppm (standard)

• Stress birefringence (@ 633 nm)：≤0.5 nm/cm/1~50 nm/cm（标准）

• Nonlinear refractive index (n ₂ @ 1064 nm)1.9 × 10 ⁻¹⁶ cm ²/W (extremely low, stable high-power laser)

• Refractive Index Temperature Coefficient (dn/dT)：

• @193 nm：-3.2×10 ⁻⁶ /K

• @248 nm：-6.9×10 ⁻⁶ /K

3、 Laser durability (key indicator of lithography level)

• Applicable wavelengthExcimer lasers at 157 nm, 193 nm, and 248 nm

• Laser damage threshold (LDT)：>10 J/cm ² @ 193 nm (10 ns pulse)

• long-term stabilityUnder deep ultraviolet lithography environmentLow defect, low agingSuitable for 7nm and below processes

4、 Size and customized specifications

• Maximum size：

• Single crystal: diameter ≤250 mmThickness ≤ 150mm

• Polycrystalline: diameter ≤440 mmThickness ≤ 150mm

• Crystal orientation:<111>(default),<100>, random orientation

• Surface qualityGrinding, polishing (λ/10, λ/20), ultra precision polishing

• toleranceDiameter/length ± 0.1 mm, thickness ± 0.05 mm (higher precision can be customized)

5、 Material grade

• UV 级 （193–400 nm）Refractive index uniformity ≤ 1 ppm, birefringence ≤ 1 nm/cm, used for193 nm lithography objective lens.

• DUV grade (157-193 nm)Ultra high uniformity (≤ 0.5 ppm), extremely low birefringence (≤ 0.5 nm/cm), compatible157 nm lithography.

• VIS grade (400-780 nm)Standard uniformity (3-5 ppm), used for visible light imaging and microscopy.

• IR 级 （0.78–9 μm）Infrared transmission optimization, used forInfrared window, thermal imaging, spectrometer.

6、 Core advantages

1. Ultra wide transmission：130 nm–9 μm， One material covers multi band requirements.

2. Extremely low dispersionAbbe number 95.23, strong color correction ability, high imaging sharpness.

3. High laser resistanceSuitable for 193/248 nm excimer laser, long-term stability without damage.

4. High uniformityThe refractive index uniformity reaches 0.5 ppm, and the beam consistency is excellent.

5. Large caliber preparationSingle crystal 250 mm, polycrystalline 440 mm, meeting the requirements of large optical systems.

7、 Typical applications

• semiconductor:193 nm/248 nm lithography objective lens and illumination system.

• Laser: high-power laser window, beam splitter, lens (157-1064 nm).

• Infrared: Infrared thermal imager window, spectrometer components, astronomical telescope lens.

• Research: Vacuum Ultraviolet (VUV) Optics, High Energy Radiation Environment Window.

Hellma German synthesized calcium fluoride (CaF ₂) optical crystal