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The KTF (potassium terbium fluoride) crystal launched by our company is a high‑performance, low‑absorption magneto‑optic crystal specifically developed for high‑power laser isolators. Leveraging our independently developed crystal growth and fabrication technology, it exhibits low absorption characteristics, enabling high‑power devices to operate stably without the need for complex cooling systems. This provides reliable core material support for high‑power laser systems, effectively driving performance upgrades and expanding the application scope of laser devices.
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Physical Property
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Value
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Remarks
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Crystal Structure
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Orthorhombic system
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Unit Cell Parameters
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a ≈ 12.82 Å, b ≈ 6.404 Å, c ≈10.616 Å
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Melting Point
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~1172 °C
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Mohs Hardness
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~5 Mohs
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Density
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~3.0 g/cm³
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Thermal Conductivity
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κ₁₁ ≈ 3.3 W/m·K, κ₂₂ ≈3.4 W/m·K, κ₃₃ ≈ 2.5 W/m·K
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Z‑direction thermal conductivity is lowest and is the main direction of thermal effect
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Thermal Expansion Coefficient
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α₁₁ ≈ 11.8 × 10⁻⁶ /K, α₂₂ ≈9.5 × 10⁻⁶ /K, α₃₃ ≈0.6 × 10⁻⁶ /K
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SHG Phase Matching Range
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~0.53–4.0 μm (Type I & Type II)
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Thermo‑optic Coefficient
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dn₃/dT ≈ 14.7 × 10⁻⁶ /K, dn₁/dT ≈ 6.0 × 10⁻⁶ /K
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Bulk Absorption Coefficient
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< 0.1 %/cm @ 1064 nm
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One of KTF’s core advantages — extremely low absorption, suitable for high‑power applications
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Acceptance Angle (Aperture Angle)
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~25 mrad·cm (Type II, 1064 nm SHG)
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Temperature Bandwidth
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~25 °C·cm (Type II, 1064 nm SHG)
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Spectral Acceptance Width
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~6.5 cm⁻¹·cm (Type II, 1064 nm SHG)
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Walk‑off Angle
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~0° (Type II NCPM, 1064 nm SHG)
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No walk‑off under non‑critical phase matching (θ = 90°) — a major advantage; walk‑off occurs under critical matching
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Nonlinear Optical Coefficients
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d₃₃ ≈ 14.7 pm/V, d₃₂ ≈ 4.7 pm/V, d₃₁ ≈ 2.6 pm/V, d₂₄ ≈ 3.6 pm/V
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Large nonlinear coefficients — basis for efficient frequency conversion
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Nonzero d Coefficients
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d₁₅, d₂₄, d₃₁, d₃₂, d₃₃
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In mm² point group, there are 5 independent nonzero nonlinear optical tensor elements
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Electro‑optic Coefficients
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r₃₃ ≈ 36.3 pm/V, r₂₃ ≈15.7 pm/V, r₁₃ ≈ 9.5 pm/V
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Large linear electro‑optic coefficients — suitable for modulators, Q‑switches, etc.
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Half‑wave Voltage (Vπ)
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~1.5–3.0 kV (depends on geometry and orientation)
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Voltage required across an electro‑optic device to produce a phase retardation of π
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Resistivity
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~10¹²–10¹⁵ Ω·cm (anisotropic)
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Relative Dielectric Constant
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ε₁₁/ε₀ ≈ 13, ε₂₂/ε₀ ≈ 13, ε₃₃/ε₀ ≈28 (@ 1 kHz)
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Specification Item
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Parameter Details
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Material
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KTF
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Phase Matching
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Type II non‑critical phase matching, θ = 90° ± 0.1°, φ = 23.5° ± 0.1°
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Wavefront Distortion
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< λ/8 @ 632.8 nm
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Crystal Size
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3 × 3 × 5 mm, 4 × 4 × 7 mm, 5 × 5 × 10 mm (L × W × H); custom sizes available upon request
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Dimensional Tolerance
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(W ± 0.1 mm) × (H ± 0.1 mm) × (L + 0.5/–0.1 mm); custom tolerances available upon request
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Parallelism
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20″
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Perpendicularity
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≤ 15′
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Flatness
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λ/8 @ 633 nm
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Surface Finish
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10–5 (MIL‑PRF‑13830B)
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Beveled Edge
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≤ 0.2 mm × 45°
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Clear Aperture
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> 95% of central area
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Coating
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Dual‑band anti‑reflection coating: Ravg < 0.1% @ 1064 nm & Ravg < 0.15% @ 532 nm
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Bulk Absorption Coefficient
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< 0.1% /cm @ 1064 nm
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Laser Damage Threshold
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> 2.0 J/cm² (10 ns pulse, 10 Hz repetition rate, @ 1064 nm, Φ 0.5 mm beam)
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Shelf Life
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12 months (must be stored sealed in a dry (< 20% RH), dust‑free, light‑protected, room‑temperature environment)
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Precision laser systems serving as pump sources for medium‑ and high‑power lasers may also utilize KTF‑based isolators for protection during semiconductor manufacturing and inspection processes.