KNbO3 is a negative biaxial crystal. It has the largest effective nonlinear optical coefficients among the commonly used inorganic crystals. Therefore, it is normally used for frequency doubling low and medium power lasers such as diode lasers, diode pumped solid state lasers and cw Nd:YAG and Ti:Sapphire lasers. It is also an efficient crystal for low oscillation threshold and high efficient optical parametric oscillators (OPO) and generators (OPG). The following are the relevant parameters:

Standard Specifications of KNbO3
Dimension tolerance: (W ± 0.1mm) x (H ± 0.1mm) x (L + 0.2mm / -0.1mm)
Transmitting wavefront distortion: less than l/4 @633nm
Clear aperture: > 90% central area
Flatness: l/4 @633nm
Surface Quality : 20/10 Scratch and Dig to MIL-O-13830A
Parallelism: better than 20 arc seconds
Perpendicularity: 5 arc minutes
Angle tolerance (degree): D(q) < ± 0.5, D(f) < ± 0.5
Coating: These standard crystals are typically supplied with dual AR coatings at the pump and signal wavelengths (R < .2% at the pump and R < 0.5% at the signal wavelength). Other options are available such as AR/HR combinations etc.


1. Because KNbO3 has small acceptance temperature, customers are advised to put KNbO3 crystal into an oven with temperature stability greater than ± 0.1°C if high stable output is required.

2. The domain structure of KNbO3 easily appears by shaking or stressing, customers are advised to handle KNbO3 crystals smoothly.

3. The KNbO3 crystal keeps its orthorhombic symmetry in temperature range from -50°C to 220°C, please don't cool KNbO3 crystal below -40°C or heat it over 210°C.

4. The KNbO3 is a good crystal for electro-optic modulation.

5. Dream Lasers provides AR-coatings and HR-coatings for KNbO3 crystal at different wavelengths. Custom cuts for other phase-matching requirements can be provided.