Potassium Dihydrogen Phosphate / Potassium Dideuterium Phosphate ( KDP, DKDP or KD*P )

Potassium Dihydrogen Phosphate / Potassium Dideuterium Phosphate KDP, DKDP, KD*P

Potassium Dihydrogen Phosphate (KDP) and Potassium Dideuterium Phosphate (DKDP) are nonlinear optical materials (NLO)know for their large NLO coefficients, wide transparency range and high optical damage threshold.

These materials are widely used as frequency multipliers for generation of the second, third and fuorth harmonics for Nd:YAG, Nd:YLF lasers. Both crystals are also applied in electro-optics: as Q-switches for Nd:YAG, Nd:YLF, Ti:sapphire and Alexandrite lasers and Pockels cells.

Owing to a posibility of growing large crystals, high laser frequency multipliers. Q-switches and Pockels cells, laser damage threshold of witch is over 40 J/cm2 (at lambda=1,06 µm, tau=3 ns).
This allows to use them in the devices for laser fusion.

KDP and DKDP crystals possess elctro-optical, nonlinear and piesoelectric properties, high laser damage threshold and are used as the base for the devices and systems of laser engineering: frequency multipliers, modulators, gates, deflectors.

Basic Properties45 KDP DKDP
Chemical Fomula KH2PO4 KD2PO4
Class of symmetry 42m 42m
Crystal structure tetragonal tretagonal
Transparency Range, mm 0,2 – 1,5 0,2 – 1,6
Wafelength range, nm 200-1500 2
Electro – optical Coefficients, pm/V-1. r41 = 8.8
r63 = 10.3
r41 = 8.8
3 = 25
Nonlinear Coefficients d36 = 0.44 pm/V d36 = 0.40 pm/V
Refractive index (at 1064 nm) n0 = 1.4938
nc = 1.4599
no = 1.4948
nc = 1.4554
Temperature Synchronism Width, oC*cm 11,5. 7,4.
Spectral Synchronism Width, A *cm 106
Angle Synchronism Width, mrad*cm 0,84 0,94
Longitudinal half-wave voltage Vn = 7.65 KV
(l = 546 nm)
Vn = 2.98 KV
(l= 546 nm)
Absorpion Coefficient, cm-1 0.07 0.006
Optical Damage Threshold
(l=1,064 mm, t=10ns)
>5 GW / cm² >3 GW / cm²
ohs Hardness 2,5 2,5
Extinction ratio   30 dB
Sellmeier equations of DKDP
n02 = 1.9575544 + 0.2901391 l2 / (l2 – 0.0281399) – 0.02824391 l2 + 0.004977826 l2
nc2 = 1.5005779 + 0.6276034 l2 / (l2 – 0.0131558) – 0.01054063 l2 + 0.002243821 l4
Sellmeier equations of KDP
n02 = 2.259276 + 0.01008956 / (l2 – 0.012942625) + 13.00522 l2 / (l2 – 400)
nc2 = 2.132668 + 0.008637494 / (l2 – 0.012281043) + 3.2279924 l2 / (l2 – 400)
Refractive Index              
Sellmeier Equation     n2 = A + B / (l2 – C) + Dl2 / (l2 – E) ( l in mm)
Sellmeier Coeficients     KDP KD*P ADP CDA CD*A
A no 2.2576 2.2409 2.3041 0.4204 2.4082
  ne 2.1295 2.1260 2.1643 2.3503 2.3458
B no 0.0101 0.0097 0.0111 0.0163 0.0156
  ne 0.0097 0.0086 0.0097 0.0156 0.0151
C no 0.0142 0.0156 0.0133 0.0180 0.0191
  ne 0.0014 0.0120 0.0129 0.0168 0.0168
D no 1.7623 2.2470 15.1086 1.4033 2.2122
  ne 0.7580 0.7844 5.8057 0.6853 0.6518
E no 57.8984 126.9205 400.0000 57 8239 126.8709
  ne 127.0535 123.4032 400.0000 127.2700 127.3309
  l = 1064 no 1.4942 1.4931 1.5071 1.5515 1.5499
Typical
Values
nm ne 1.4603 1.4583 1.4685 1.5356 1.5341
  l = 532 no 1.5129 1.5074 1.5280 1.5732 1.5692
Typical
Values
nm ne 1.4709 1.4683 1.4819 1.5516 1.5496
  l = 355 no 1.5317 1.5257 1.5487 1.6026 1.5974
  nm ne 1.4863 1.4833 1.4994 1.5788 1.5759