PPKTP Crystal for Quantum Technologies

What is PPKTP?

PPKTP (periodically poled potassium titanyl phosphate) is KTP micro-structured with alternating ferroelectric domains so it can be quasi-phase matched (QPM). Like PPLN, the periodic poling lets PPKTP use its largest nonlinear coefficient and reach any conversion wavelength within its transparency, with no spatial walk-off. PPKTP is especially valued in quantum optics because of its low noise at visible wavelengths and good photorefractive resilience.

Why PPKTP for quantum technologies

The core quantum process is spontaneous parametric down-conversion (SPDC): a pump photon splits into a pair of lower-energy photons that are entangled in time, energy and polarisation. These pairs are the raw material of photonic quantum computing, quantum communication and fundamental tests of quantum mechanics. PPKTP's high effective nonlinearity (d_eff ~10 pm/V), low absorption at visible/near-IR wavelengths, and engineerable poling period make it one of the most efficient sources of high-quality entangled pairs, and it is also used for squeezed light and tunable OPOs.

Applications

PPKTP is used for entangled-photon-pair generation (SPDC), heralded single-photon sources, squeezed-light sources for precision metrology and quantum sensing, and compact tunable OPOs. Compared with PPLN, PPKTP often offers lower noise in the visible — see also our PPLN article and the BBO vs LBO vs KTP comparison.

Frequently asked questions

PPKTP vs PPLN for entangled photons? Both work via QPM/SPDC; PPKTP often gives lower visible-wavelength noise and good resilience, while PPLN offers a higher d₃₃ but needs MgO doping for damage resistance.

How are photon pairs generated? A pump photon undergoes SPDC in the poled crystal and splits into an energy- and time-entangled pair at the designed wavelengths.

Is the poling period fixed? It is set for the target pump/signal/idler wavelengths; AOG can advise on period and coating — contact sales@aogcrystal.com.