KDP (Potassium Dihydrogen Phosphate)

Potassium Dihydrogen Phosphate (KDP) and Potassium Dideuterium Phosphate (KD*P) crystals are among the most widely-used commercial NLO materials. They feature good UV transmission, high damage threshold and high birefringence, though their NLO coefficients are relatively low. They are commonly used for doubling, tripling and quadrupling of Nd:YAG lasers at room temperature. In addition, they are also excellent electro-optic crystals with high electro-optic coefficients, widely used as electro-optical modulators, Q-switches, and Pockels Cells, etc.

Features:

  • Strong UV transmission
  • High optical damage threshold
  • High birefringence
  • High nonlinear coefficients

Applications:

  • Second, third, and fourth harmonic generation of Nd:lasers
  • Frequency doubling of dyer laser
  • High power laser frequency conversion materials
  • Shutter for high speed photography
  • Electro-optical modulator and Q switches

Physical and Optical Properties:

  KDP KD*P(DKDP)
Chemical Formula KH2PO4 KD2PO4
Crystal Structure Tetragonal Tetragonal
Transmission Range 200-1500nm 200-1600nm
Nonlinear Coefficients d36=0.44pm/V d36=0.40pm/V
Refractive Indcies (at 1064nm) no=1.4938, ne=1.4599 no=1.4948, ne=1.4554
Electro-Optical Coefficients r41=8.8pm/V r63=10.3pm/V r41=8.8pm/V r63=25pm/V
Longitudinal Half-Wave Voltage Vp=7.65KV(l=546nm) Vp=2.98KV(l=546nm)
Absorption 0.07/cm 0.006/cm
Temperature Synchronism Width 11.5oC*cm 7.4oC*cm
Spectral Synchronism Width 106Ã*cm 32Ã*cm
Angle Synchronism Width 0.84 mrad*cm 0.94 mrad*cm
Absorption Coefficient, cm-1 0.07 0.006
Mohs Hardness 2.5 2.5
Optical Damage Threshold >5 GW/cm2 >3 GW/cm2
Extinction Ratio   30dB

 

Sellmeier Equations:

KDP no2 = 2.259276 + 0.01008956/(l2 - 0.012942625) + 13.005522l2 /(l2 - 400)
ne2 = 2.132668 + 0.008637494/(l2 - 0.012281043) + 3.2279924l2/(l2 - 400)
DK*P no2 = 1.9575544 + 0.2901391/(l2 - 0.0281399) - 0.02824391l2 +0.004977826l4
ne2 = 1.5005779 + 0.6276034/(l2 - 0.0131558) - 0.01054063l2 +0.002243821l4

 

KD*P Single Crystals - commonly used cut

Designation Operation Input Output
53.7° SHG (II) 1064 nm 532 nm
59.5° THG (II) 1064 nm + 532 nm 355 nm
63.7° SFM (II) 1064 nm + (421-1000 nm) 302 - 515 nm
86° FHG (I) angle tune 532 nm 266nm
90° FHG (I) temp. tune 532 nm 266 nm
36.6° SHG (I) 1064 nm 532 nm
46.8° THG(I) 1064 nm + 532 nm 355 nm

 

DKDP's Specifications:

Wavefront Distortion: less than l/8 @ 633nm
Dimension Tolerance: (W± 0.1mm) x (H±0.1mm) x (L + 0.2mm/-0.1mm)
Clear Aperture: > 90% central area
Flatness: l/8 @ 633nm
Scratch/Dig Code: 10/5 to MIL-O-13830A
Parallelism: better than 20 arc seconds
Perpendicularity: 5 arc minutes
Angle Tolerance: qD <±0.3°, fD <±0.3°
Quality Warranty Period: one year under proper use

 

Download in PDF Format:

Datasheet (PDF)