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KDP KD*P Crystal
Potassium Dihydrogen Phosphate (KDP) and Potassium Dideuterium Phosphate (KD*P, DKDP) are among the most widely-used commercial NLO crystals, characterized by good UV transmission, high damage threshold, and high birefringence, though their NLO coefficients are relatively low. KDP crystals are usually used for doubling, tripling and quadrupling of a Nd:YAG laser at the room temperature. KD*P are excellent electro-optic crystals with high electro-optic coefficients, widely used as electro-optical modulators, such as Q-switches, Pockels Cells, etc.
KDP and KD*P are hygroscopic, a sealed housing with transmitting windows is recommended for protection of the crystal faces.
KDP/KD*P Physical and Optical Properties
| Property | KDP | KD*P |
| Chemical Formula Transparency Range Nonlinear Coefficients Refractive Index (at 1064nm) Electro-Optical Coefficients Longitudinal Half-Wave Voltage: Absorptance: Damage Threshold: Extinction Ratio: |
KH2PO4 200-1500nm d 36 =0.44pm/V No=1.4938, Ne=1.4599 r41=8.8pm/V, r63=10.3pm/V Vp =7.65KV @546nm 0.07/cm >5 GW/cm² 30dB |
KD2PO4 200-1600nm d 36 =0.40pm/V No=1.4948, Ne=1.4554 r41=8.8pm/V, r63=25pm/V Vp =2.98KV @546nm 0.006/cm >3 GW/cm² 30dB |
Sellmeier Equations of KDP (λ in μm):
No 2 = 2.259276 + 0.01008956/( λ2 - 0.012942625) +13.005522λ2
/(λ2 - 400)
Ne 2 = 2.132668 + 0.008637494/( λ2 - 0.012281043) +3.2279924λ2
/(λ2 - 400)
Sellmeier Equations of KD*P (λ in μm):
No 2 = 1.9575544 + 0.2901391/( λ2 - 0.0281399) - 0.02824391λ2 +0.004977826
λ4
Ne 2 = 1.5005779 + 0.6276034/( λ2 - 0.0131558) - 0.01054063λ2 +0.002243821
λ4
KDP/KD*P Specifications
Surface Quality: 10-5 Scratch-dig
Flatness: <λ/8 @633nm
Chamfer: 0.1mm@45deg.
Clear Aperture: Central 90% of Diameter
Parallelism: <10 arc seconds
Perpendicular: <10 arc minutes
Orientation Angle: +/-0.25deg.
Damage Threshold: 0.3GW/cm2@1064nm10ns
Coating: Dual wavelength AR coating: R<0.2%