Crystals Land

  DKDP  KDP

Potassium Dihydrogen Phosphate (KDP) and Potassium Dideuterium Phosphate (DKDP) are one of the most widely-used commercial NLO crystals. KDP and DKDP crystals are commonly used for doubling, tripling of Nd:YAG laser at the room temperature. In addition, they are also excellent electro-optic crystals with high electro-optic coefficients, widely used as electro-optical modulators.

Physical and Optical Properties:

		KDP	DKDP (KD*P)
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 Indices (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		11.5 oC*cm	7.4 oC*cm
Spectral Synchronism Width		106 Å*cm	32 Å*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
DKDP	no2 = 1.9575544 + 0.2901391/(l2 - 0.0281399) - 0.02824391l2 +0.004977826l4 ne2 = 1.5005779 + 0.6276034/(l2 - 0.0131558) - 0.01054063l2 +0.002243821l4

 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
P perpendicularity:	5 arc minutes
Angle tolerance:	Dq < ± 0.3°, Df < ±0.3°

Application:

• Good UV transmission
• High optical damage threshold

Note:

KDP, DKDP is hygroscopic, so a dry condition (<50%) and the sealed housing for preventing it from moisture has to be considered.