Comparing BBO, LBO, and KDP Crystals
Where KDP and DKDP fit
BBO and LBO dominate everyday frequency conversion, but KDP (KH2PO4) and DKDP (KD2PO4) remain the crystals of choice for the very largest apertures and highest pulse energies — most famously the meter-scale SHG and frequency-conversion cells in inertial-confinement-fusion and high-energy laser drivers. They can be grown to huge size at relatively low cost, and DKDP's lower nonlinear coefficient is offset by the ability to use enormous crystals. BBO and LBO, by contrast, offer higher nonlinearity and damage threshold in compact crystals for laboratory and industrial lasers.
| Property | BBO | LBO | KDP / DKDP |
|---|---|---|---|
| Nonlinear coefficient | ~2.0 pm/V | ~0.8–1.2 pm/V | Lower (~0.4 pm/V) |
| Aperture available | Small–medium | Small–medium | Very large (meter-scale) |
| Damage threshold | High | Very high | Moderate–high |
| Hygroscopic | Mildly | Slightly | Yes (needs controlled environment) |
| Best use | UV, OPO, compact THG/4HG | High-power SHG/THG, NCPM | Very large-aperture, high-energy SHG |
Choosing among them
For compact, efficient conversion in a research or industrial laser, BBO or LBO is usually the answer (see our BBO vs LBO vs KTP guide). Reach for KDP/DKDP only when you need very large apertures and very high pulse energies that BBO/LBO crystals simply cannot be grown to.
Frequently asked questions
Why use KDP/DKDP if their nonlinearity is low? They can be grown to enormous size cheaply, so a large crystal compensates for the low coefficient — essential for high-energy, large-beam systems.
Are KDP/DKDP hygroscopic? Yes — they must be kept in a controlled environment, which is acceptable in large laser facilities. View our KDP/DKDP crystals.
For more information on crystal materials, please consult info@aogcrystal.com