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.
Potassium dihydrogen phosphate (KH2PO4, KDP) and potassium dideuterium phosphate (KD2PO4, DKDP) crystals 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:
- Laser frequency conversion — harmonic generation for high pulse energy;
- Electro-optical modulation;
- Q-switching crystal for Pockels cells;
Advantages:
- Good UV transmission;
- High birefringence
- High optical damage threshold;
- High nonlinear coefficients;
- Non-hygroscopic, chemically and mechanically stable
- Wide working temperature range
- 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=1.4938，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 | 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 |
|
KDP or DKDP specifications:
| Tolerance of cutting angle | △θ≤±0.25°,△φ≤±0.25° |
| Tolerance of dimension | Dimension+0/-0.1 mm，L：±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 |
