Calcite (CaCO₃) Single Crystal

Advantages

• Extremely high birefringence: Δn = −0.1705 at 630 nm, the largest among commonly available optical crystals, making it the preferred material for high-extinction-ratio polarizers .
• Broad spectral transmission: 350–2300 nm.
• Low hygroscopic susceptibility: Chemically stable under normal handling conditions .
• Glan-Thompson and Glan-Taylor polarizers made from calcite shown good extinction ratios.

Typical Specifications

• Chemical formula: CaCO₃, is the only natural mineral single crystal in our production line.
• Crystal structure: Trigonal (rhombohedral), a = 4.989 Å, c = 17.062 Å; negative uniaxial with nₒ = nₐ = n_b, nₑ = n_c
• Transparency range: 350–2300 nm (extended useful range 200–2500 nm reported by some sources)
• Refractive indices:
  • @ 0.63 μm: nₒ = 1.6557, nₑ = 1.4852, Δn = −0.1705
  • @ 1.30 μm: nₒ = 1.6629, nₑ = 1.4885, Δn = −0.1744
• Walk-off angle: ρ = 6.20° @ 0.63 μm; ρ = 6.32° @ 1.30 μm (at 45° incidence)
• Mohs hardness: 3 (soft, easily scratched; requires careful handling)
• Density: 2.71 g/cm³
• Melting point: 1339 °C (some sources cite 730 °C; the discrepancy may reflect decomposition temperature)
• Thermal expansion coefficients: αₐ = 24.39 × 10⁻⁶/K; αc = 5.68 × 10⁻⁶/K
• Damage threshold: >1 GW/cm² (typical for AR-coated polarizers)
• Optical homogeneity: λ/8 wavefront distortion for polarizer-grade.
• Sellmeier equations (λ in μm) : nₒ² = 2.69705 + 0.0192064/(λ² − 0.01820) − 0.0151624λ² nₑ² = 2.18438 + 0.0087309/(λ² − 0.01018) − 0.0024411λ²

Main Applications

• Polarizing prisms: Glan-Thompson, Glan-Taylor, and Glan-laser polarizers; Glan-Thompson designs offer the largest acceptance angle and lowest transmission loss among calcite polarizer types.
• Beam displacers and beam splitters: Polarization beam displacers and Wollaston prisms for visible and near-IR applications.
• Laser gates and Q-switches: Calcite-based laser gates and polarization control elements.
• Group-velocity delay compensators: Used in femtosecond laser systems for polarization-mode dispersion management.
• Spectroscopic polarimetry: High-precision polarization analysis in spectroscopy and ellipsometry.