Spectroscopic properties of Cr3+ ions in KTP single crystals

The possibility of creation of self-frequency doubling laser crystal based on crystal KTP doped with chromium ions is investigated. The spectral properties of Cr3+ ions are researched. The magnitude of emission cross-section at the wavelength of 833 nm corresponding to the maximum of vibronic transition 4T2-4A2 of Cr3+ ion is estimated. The excited state lifetimes at room and liquid nitrogen temperatures are determined. The spectroscopic investigations show that impurity Cr3+ ions in KTP crystal are placed in positions with weak crystal field: Dq equals 1507 cm-1, B equals 652 cm-1, C equals 2800 cm-1. The configuration diagram model with one excited state is discussed. The main features of fluorescence spectra and the expected laser emission in the near IR range form 700 to 1000 nm are considered.