KTP crystal (potassium titanyl phosphate KTiOPO4) has a large nonlinear coefficient, low temperature sensitivity, good mechanical properties, and no deliquescence. It is one of the crystals with the best comprehensive properties among nonlinear crystals. It is widely used in commercial and military lasers. Including laboratory and medical systems, range detectors, lidar, optical communications and industrial laser systems. However, the poor UV transmittance limits its application in the UV region.

Frequency-doubling (SHG) of neodymium-doped crystal lasers for green/red output
Solid-state laser frequency mixing (SFM) such as neodymium-doped crystals to obtain blue light output
OPG, OPA and OPO get dimming in the range of 0.6um-4.5um
Electro-optical (E-O) modulation, optical switch
Optical Waveguide, Fabrication of Periodically Polarized KTP Devices
Nd laser frequency doubling and frequency mixing applications

KTP is most commonly used in lasers for frequency-doubling Nd:YAG and other Nd-doped crystals, especially in green lasers. So far, intra-cavity and extra-cavity frequency-doubling Nd-doped lasers using KTP are gradually replacing visible dye lasers and tunable sapphire lasers. In many industrial studies, this laser is widely used as a green light source

– 0.5% Nd:YVO4 and KTP crystal pumped by 15W diode, 8W green output can be obtained
– 2% 3*3*1 Nd:YVO4 and 2*2*5 KTP crystal pumped by 1W diode, 180mW green output can be obtained
– 1% 3*3*1 Nd:YVO4 and 2*2*5 KTP crystal pumped by 2W diode, 300mW green output can be obtained
– 1% 3*3*2 Nd:YVO4 and 3*3*5 KTP crystals pumped by 3W diodes, 500mW green light output can be obtained

So far, KTP has become the first choice for the use of extra-cavity and intra-cavity frequency-doubling Nd lasers, and its output green laser has been used in scientific research, medical, industrial and commercial applications. Through extracavity KTP frequency doubling, using 900mJ injection seed Q-switched Nd: YAG laser can achieve 80% conversion efficiency and can output 700mJ green laser.

Particularly suitable for diode-pumped Nd lasers, KTP is a basic nonlinear optical crystal for visible solid-state lasers. Recently, intracavity frequency-doubled Nd:YVO4 and Nd:YAG lasers have been used in display, manufacturing, optical disc, and laser printers. LD-pumped Nd:YVO4 and Nd:YAG lasers have been able to obtain green lasers of more than 200mW TEM00 mode. Through mode-locking technology, 5.3W LD-pumped Nd:YAG intracavity frequency doubling can generate 3W TEM00 mode green lasers. In addition, 2.5mW green light can also be obtained by an intracavity frequency-doubling 50mW LD-pumped Nd:YVO4 compact laser with a cavity length of only 9mm.

KTP is also a powerful crystal for frequency doubling and mixing of lasers from about 1um to 3.4um. The angle of the frequency multiplication phase matching and the effective frequency multiplication coefficient (deff) are shown in the XY plane (0.9um-1.08um) and XZ plane (1.1um-3.3um) of the KTP. Although KTP can be phase-matched from 1um to 3.45um in the YZ plane (Type I), it is rarely used due to its extremely low effective nonlinear coefficient (deff).