KDP/KD*P Crystals

Characterized by the excelent UV transmission, high damage threshold, and high birefringence, KDP (Potassium Dihydrogen Phosphate) and KD*P (Potassium Dideuterium Phosphate) are useful commercial NLO materials for doubling, tripling and quadrupling of Nd:YAG laser at room temperature or an elevated temperature. They are also excellent electro-optic (EO) crystals with high electro-optic coefficients, widely used as electro-optical modulators and Pockels cells for Q-switched lasers. One disadvantage of KDP/KD*P crystals is that they are highly hygroscopic, therefore, protective coating or a sealed housing with transmitting windows is recommended for protection of polished crystal faces.

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Model	Name	application	thickness	attr_size	Price	Availability	Action
DKDP4200-NCPM532(I)	DKDP crystal, 4x4x20mm, theta=90, phi=45 for NCPM SHG of 532nm to generate 266nm (FHG of 1064nm) at ~ 55 degC, the two 4x4mm faces polished, unmounted	532nm NCPM(I)	20.0 mm	4x4x20mm	Ask
DKDP5200-NCPM532(I)	DKDP crystal, 5x5x20mm, theta=90, phi=45 for NCPM SHG of 532nm to generate 266nm (FHG of 1064nm) at ~ 55 degC, the two 5x5mm faces polished, unmounted	532nm NCPM(I)	20.0 mm	5x5x20mm	Ask
KDP10010-SHG800(I)-AR	KDP crystal, size 10x10x1.0mm, theta=44.9 for Type I SHG of 800nm to generate 400nm, the two 10x10mm faces AR coated @800/400nm	800nm SHG(I)	1.0 mm		Ask	Out Of Stock
KDP10100-SHG800(I)	KDP crystal, size 10x10x10.0mm, theta=44.9, phi=45 for Type I SHG of 800nm to generate 400nm, the two 10x10mm faces uncoated, unmounted	800nm SHG(I)	10.0 mm		Ask

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Basic Physical and Optical Properties:

	KDP	KD*P(DKDP)
Chemical Formula	KH₂PO4	KD₂PO₄
Crystal Structure	Tetragonal	Tetragonal
Transmission Range	200-1500 nm	200-1600 nm
Nonlinear Coefficients	d36=0.44 pm/V	d36=0.40 pm/V
Refractive Indices (at 1064 nm)	no=1.4938, ne=1.4599	no=1.4948, ne=1.4554
Electro-Optical Coefficients	r41=8.8 pm/V r63=10.3 pm/V	r41=8.8 pm/V r63=25 pm/V
Mohs Hardness	2.5	2.5
Surface Damage Threshold (@10 Hz, 10 ns, 1064 nm )	0.5 GW/cm²	0.5 GW/cm²
Sellmeier Equations of KDP (λ in µm)	no² = 2.259276 + 13.005522λ²/(λ² - 400)+ 0.01008956/(λ² - 0.012942625) ne² = 2.132668 +3.2279924λ2/(λ² - 400) + 0.008637494/(λ²- 0.012281043)
Sellmeier Equations of KD*P (λ in µm)	no² = 2.240921 + 2.246956λ²/(λ² -126.92073)+ 0.009676/(λ² - 0.0156203) ne² = 2.126019 + 0.784404λ²/(λ² - 123.40344) + 0.008578/(λ²- 0.0119913)

Cut Orientations for KDP/KD*P Crystal

Process (PM type)	KDP		KD*P
Process (PM type)	Orientation	Deff(pm/V)	Orientation	Deff(pm/V)
SHG (II): 1064 nm -> 532 nm	58.9	0.34	53.5°	0.34
THG (II): 1064+532 -> 355 nm	58.4	0.37	59.4°	0.33
SFG (II): 1064+(421-1000 nm) -> 302-515 nm	61.0	0.36	63.7°	0.31
FHG (I): 532 nm -> 266 nm	76.7	0.46	85.9°	0.43
NCPM FHG (I): 532 -> 266 nm	90°(T=250°C)	0.47	90°(T=55°C)	0.43
SHG (I): 1064 nm -> 532 nm	41.1	0.26	36.6°	0.22
THG(I): 1064+532 -> 355 nm	47.4	0.32	46.8°	0.29

Specifications on finished crystals:

Wavefront distortion:	less than λ/8 @ 633 nm
Dimension tolerance:	(W ± 0.1 mm) x (H ± 0.1 mm) x (L + 0.2/-0.1 mm)
Clear aperture:	> 90% central area
Flatness:	λ/8 @ 633 nm
Surface Quality:	Scratch/Dig 10/5 per MIL-O-13830A
Parallelism:	better than 20 arc seconds
Perpendicularity:	5 arc minutes
Angle tolerance:	Δθ < +/-0.5 deg, Δφ < +/-0.5 deg

Crystal Handling:

KDP, KD*P are highly hygroscopic and have to be used/stored in a very dry environment. A small enclosure (with openings for light) may be built around the crystal with a continuous flow of dry nitrogen or air into the enclosure. The dry nitrogen/air pressure needs only to be slightly above the atmosphere to keep the small volume around the crystal dry and clean.

Coating:

Single layer protective coating or anti-reflection coatings are available upon request.

Uncoated crystals can also be housed in a sealed housing with AR coated windows (shown at the right).