KTA (KTiOAsO₄) Single Crystal

Advantages

• Higher SHG figure of merit and larger electro-optic coefficients compared with its isomorph KTP.
• Wide transparency range: 350–5300 nm, extending further into the mid-infrared than KTP.
• Low mid-IR absorption: Significantly reduced absorption in the 2.0–5.0 μm band, solving the absorption peak problem of KTP near 3.4 μm.
• High laser damage threshold: >500 MW/cm² at 1064 nm (10 ns, 10 Hz, AR-coated), attributed to lower ionic conductivity and reduced absorption.
• Broad angular and temperature bandwidth: Enables flexible phase-matching configurations with small walk-off angle.
• Non-hygroscopic and chemically stable: Suitable for long-term device integration.

Typical Specifications

• Crystal structure: Orthorhombic, point group mm2; isostructural with KTP (As replaces P)
• Lattice parameters: a = 13.103–13.125 Å, b = 6.558–6.572 Å, c = 10.746–10.786 Å
• Transmission range: 350–5300 nm
• SHG phase-matching range: 1083–3789 nm
• Nonlinear coefficients: d₃₁ = 2.76 pm/V, d₃₂ = 4.74 pm/V, d₃₃ = 18.5 pm/V, d₁₅ = 2.3 pm/V, d₂₄ = 3.2 pm/V
• Electro-optic coefficients (low frequency): r₃₃ = 37.5 pm/V, r₂₃ = 15.4 pm/V, r₁₃ = 11.5 pm/V
• Absorption coefficient: <0.05%/cm at 1064 nm; <5%/cm at 3475 nm
• Laser damage threshold: >500 MW/cm² at 1064 nm (10 ns, 10 Hz, AR-coated); 300 ± 30 MW/cm² at 532 nm
• Mohs hardness: ~5
• Density: 3.454 g/cm³
• Melting point: 1130 °C
• Thermal conductivity: k₁ = 1.8 W/(m·K), k₂ = 1.9 W/(m·K), k₃ = 2.1 W/(m·K)

Sellmeier equations (λ in μm):
nₓ² = 1.90713 + 1.23522λ²/(λ² − 0.19692²) − 0.01025λ²
nᵧ² = 2.15912 + 1.00099λ²/(λ² − 0.21844²) − 0.01096λ²
n_z² = 2.14768 + 1.29559λ²/(λ² − 0.22719²) − 0.01436λ²

Main Applications

• Primary application for mid-IR generation (up to ~4 μm), with demonstrated energy conversion efficiencies exceeding 50% in OPO configurations. A KTA OPO pumped at 1.064 μm achieved 20% maximum conversion efficiency.
• DFG: Tunable mid-IR source from 3.4 to 5.3 μm by mixing 532 nm and dye laser output.
• SHG: Frequency doubling of 1083–3789 nm radiation.
• Terahertz wave generation: High birefringence (Δn ≈ 0.76) and phase-matching capability in the XZ-plane make KTA a candidate for THz generation via DFG.
• Coexisting OPO and stimulated Raman scattering: Demonstrated in a single KTA crystal, enabling multi-wavelength output in an intracavity configuration.