Potassium Dihydrogen Phosphate (KDP) and Potassium Dideuterium Phosphate (KD*P, DKDP) crystals
Potassium Dihydrogen Phosphate (KDP) and Potassium Dideuterium Phosphate (KD*P, DKDP) crystals are
amongst the most widley used nonlinear crystals. Both of these crystals are routinely used for the doubling, tripling and quadrupling of Nd:YAG lasers at room temperatures. In addition, their excellent electro-optic coefficients mean that they are widely employed as EO modulators, Q-switches and Pockels cells.

DKDP / KD*P crystal strengths include:
  • Good UV transmission
  • High optical damage threshold
  • High birefringence
  • High nonlinear coefficients

DKDP / KD*P applications include:
  • SHG with high pulse energy, low repetition rate (<100Hz) Q-switched and mode-locked Nd:YAG
  • THG with high pulse energy Q-switched and mode-locked Nd:YAG via sum frequency generation
  • FHG with high pulse energy Q-switched and mode-locked Nd:YAG
  • EO modulation
  • Q-switching
  • SHG and THG using high power Nd:YAG (1342 and 1319nm)
  • OPO and OPO applications
  • Can be pumped by a wide range of sources.
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DKDP / KD*P Crystal - Availability
  • Format:
Rods, Discs and Slabs
  • Sizes:
Diameter: 80mm max and Length: 80mm max
DKDP / KD*P Crystal Properties
Optical Properties Units Value
Transmission/
Transparency Range		 µm 200 - 2150
Refractive Index (n) @1064nm n₀ = 1.4931
ne = 1.4583
@532nm n₀ = 1.5074
ne = 1.4683
@355nm n₀ = 1.5257
ne = 1.4833
@266nm n₀ = 1.5539
ne = 1.5071
Non-linear Coefficient @1.06µm (d₃₆) pm/V 0.4
Effective Nonlinear Coefficients: Type I:
dooe=d₃₆ x sinθ x sin2φ

Type II:
deoe=d₃₆ x sin2θ x cos2φ
Absorption Coefficient @1.06µm cm‾¹ 0.005
Physical / Thermal Properties Units Value
Chemical Formula KD₂PO₄
Crystal Symmetry/
Structure		 Tetragonal
Point Group 42m
Melting Point ºC 240
Thermal Expansion Coeff. @20ºC 10‾⁶/ºC ┴19.0

║ 44
Thermal Conductivity Coeff. @20ºC W/m/ºK ┴1.9

║ 2.1
Specific Heat Capacity J/g K TBA
Density g/cm³ 2.355
Mohs Hardness 2.5
Optical Damage Threshold @1.06/ºC,10ns GW/cm² 0.5
DKDP / KD*P Crystal - Sellmeier Equations
no² = 1.9575544 + 0.2901391/(λ² - 0.0281399) - 0.02824391λ²+0.004977826λ⁴

ne² = 1.5005779 + 0.6276034/(λ² - 0.0131558) - 0.01054063λ² +0.002243821λ⁴
DKDP / KD*P Crystal - Common Configurations
Application/
Operation		 Input
nm		 Output
nm
 Theta Phi
SHG (Type II) 1064 532 53.7 0
THG (Type II) 1064+532 355 59.5 0
SFM (Type II) 1064+
(421-1000)		 302 - 515 63.7 0
FHG (Type I) - Angle Tune 532 266 86 0
FHG (Type I) - Temp Tune 532 266 90 0
SHG (Type I) 1064 266 36.6 0
THG (Type II) 1064 + 532 532 46.8 0