KDP (Potassium Dihydrogen Phosphate)
Potassium Dihydrogen Phosphate (KDP) and Potassium Dideuterium Phosphate (KD*P) crystals are among the most widely-used commercial NLO materials. They feature good UV transmission, high damage threshold and high birefringence, though their NLO coefficients are relatively low. They are commonly used for doubling, tripling and quadrupling of Nd:YAG lasers at room temperature. In addition, they are also excellent electro-optic crystals with high electro-optic coefficients, widely used as electro-optical modulators, Q-switches, and Pockels Cells, etc.
Features:
- Strong UV transmission
- High optical damage threshold
- High birefringence
- High nonlinear coefficients
Applications:
- Second, third, and fourth harmonic generation of Nd:lasers
- Frequency doubling of dyer laser
- High power laser frequency conversion materials
- Shutter for high speed photography
- Electro-optical modulator and Q switches
Physical and Optical Properties:
| KDP | KD*P(DKDP) | |
| 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 Indcies (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 | 11.5oC*cm | 7.4oC*cm |
| Spectral Synchronism Width | 106Ã*cm | 32Ã*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) |
| DK*P | no2 = 1.9575544 + 0.2901391/(l2 - 0.0281399) - 0.02824391l2 +0.004977826l4 ne2 = 1.5005779 + 0.6276034/(l2 - 0.0131558) - 0.01054063l2 +0.002243821l4 |
KD*P Single Crystals - commonly used cut
| Designation | Operation | Input | Output |
| 53.7° | SHG (II) | 1064 nm | 532 nm |
| 59.5° | THG (II) | 1064 nm + 532 nm | 355 nm |
| 63.7° | SFM (II) | 1064 nm + (421-1000 nm) | 302 - 515 nm |
| 86° | FHG (I) angle tune | 532 nm | 266nm |
| 90° | FHG (I) temp. tune | 532 nm | 266 nm |
| 36.6° | SHG (I) | 1064 nm | 532 nm |
| 46.8° | THG(I) | 1064 nm + 532 nm | 355 nm |
DKDP's 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 |
| Perpendicularity: | 5 arc minutes |
| Angle Tolerance: | qD <±0.3°, fD <±0.3° |
| Quality Warranty Period: | one year under proper use |
Download in PDF Format:
Datasheet (PDF)