KDP & DKDP Crystal Potassium Dihydrogen Phosphate and Potassium Dideuterium Phosphate

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



Descriptions:

KDP Potassium Dihydrogen Phosphate and KD*P or DKDP Potassium Dideuterium Phosphate are one of the oldest used nonlinear materials. DKDP and KDP are known as analogs, though their properties differ due to DKDP deuteration. They both exhibit excellent ultraviolet transmission and high damage threshold. The nonlinearity of these crystals is relatively low, these crystals can be grown in large size. They found their application as nonlinear frequency doublers, triplers, and quandruplers of Nd-doped lasers and as Q-switch devices for Ti:Sapphire, Alexandrite, Nd-doped lasers. The main drawback is that these crystals are highly hygroscopic, therefore sealed housing and dry operating conditions have to be ensured.


Main applications:

1) Laser frequency conversion — harmonic generation for high pulse energy;

2) Electro-optical modulation;

3) Q-switching crystal for Pockels cells;


Advantages:

1) Good UV transmission;

2) High birefringence

3) High optical damage threshold;

4) High nonlinear coefficients;

5) Non-hygroscopic, chemically and mechanically stable

6) Wide working temperature range

7) Low capacitance


Basic properties

KDP

DKDP / KD*P

Chemical Formula

KH2PO4

KD2PO4

Transparency Range

200-1500nm

200-1600nm

Nonlinear Coefficients

d36=0.44pm/V

d36=0.40pm/V

Refractive index@1064nm

no=1.4938ne=1.4599

no=1.4948ne=1.4554

Electro-optical Coefficients

r41=8.8pm/V

r63=10.3pm/V

r41=8.8pm/V

r63=25pm/V

Longitudinal half-wave voltage

Vπ=7.65KV(λ=546nm)

Vπ=2.98KV(λ=546nm)

Absorptance

0.07/cm

0.006/cm

Optical damage threshold

5GW/cm2

3GW/cm2

Extinction ratio

30dB

Sellmeier equations of KDP (λ in μm)

no2=2.259276+0.01008956/(λ2-0.012942625)+13.00522λ2/(λ2-400)
ne2=2.132668+0.008637494/(λ2-0.012281043)+3.2279924λ2/(λ2-400)

Sellmeier equations of KD*P (λ in μm)

no2=1.9575544+0.2901391λ2/(λ2-0.0281399)-0.02824391λ2+0.004977826λ4
ne2=1.5005779+0.6276034λ2/(λ2-0.0131558)-0.01054063λ2+0.002243821λ4



HGO offers KDP or DKDP specifications:

Tolerance of cutting angle

△θ≤±0.25°,△φ≤±0.25°

Tolerance of dimension

Dimension+0/-0.1 mmL±0.1mm

Flatness

λ/10 @ 632.8nm

Wavefront distortion

λ/8@ 632.8nm

Surface quality

10/5 per MIL-O-13830A

Parallelism

20

Perpendicularity

10

Clear Aperture:

> 90%

Chamfer:

< 0.1 mm @ 45°

Size

Upon customer request

Coating

AR/HR coating upon customer’s request

Damage Threshold

750MW/CM2 at 1064nm, TEM00, 10ns, 10Hz

Quality Warranty Period

One year under proper use

Why Choose HGO ?

HGO supplies high quality KDP and KD*P crystals for various applications. Because their polished surfaces are easier to be moistened, the user is advised to provide the dry condition (<50%) and the sealed housing for preservation. For this purpose, HGO also provides polishing and sealed housing services for the KDP-based crystals. Our engineers will serve you to select and design the best crystal, according to the laser parameters you provide.



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