Characterization of domain gratings in KTP and RKTP crystals for second harmonic generation.

Abstract: Lasers are used in a vast range of applications ranging from eye surgery to devices formeasuring air pollution. Most of these applications require specific wavelengths that cannot be obtained by regular lasers. Therefore it is important to be able to convert the wavelength of the laser to the desired wavelength for a specific application. This is achieved by using nonlinear optical crystals in which an incoming light frequency can be converted into another. Due to the material’s chromatic dispersion there is a phase mismatch between the incoming and generated light, which prevents a net increase of the generated light’s power. A solution to this problem is the creation of domain gratings in ferroelectric crystals, which compensates for the phase mismatch between the interacting photons. However, the conversion efficiency will depend on the quality of the grating. In this study, we have characterized KTiOPO4 and Rb‐doped KTiOPO4 ferroelectric crystals in terms of their efficiency to convert infrared light to blue light. This conversion efficiency has been correlated to the domain structure and the quality of the grating. We have found that the homogeneity of the grating and the existence of damage on the crystal’s optical surfaces have a strong impact on the conversion efficiency.