The calcium and rare earth oxo-borates, Ca4ReO(BO3)3 (Re = Gd, Y, La): synthesis and investigations of new non-critical phase matching configurations for frequency conversion at specific laser wavelengths

Visible and UV lasers are currently investigated for many applications as data storage, medicine, etc. Intracavity frequency doubling appears as a good solution. Thus, the non-linear family Ca4REO(BO3)3 (RE = rare earth, RECOB) has shown a considerable interest to produce compact visible laser. In addition, it is possible to tune the compositions of RECOB by partial substitutions in order to achieve non-critical phase matching (NCPM). In the present work, various cationic substitutions have been studied in solid solutions as Gd1-xYxCOB, Gd1-xLaxCOB, Gd1-xScxCOB (for the first time), Re1-xBixCOB (REe = Gd or Y) and (Ca1-xSrx)4GdO(BO3)3 in order to investigate their crystal growth and adjust the NCPM wavelength by composition. The wavelength range is related to neodymium doped laser materials emitting on the 4F3/2-4I9/2 transition, for example Nd:YAP (YAlO3) at 930 nm, Nd:YAG (Y3Al5O12) at 946 nm or Nd:ASL (Sr1-xNdyLax-yMgxAl11-xO19) at 900 nm. We have also demonstrated that the compositions for NCPM can be determined from the refractive index of both lattices M1-xM'xCOB (M, M' RE) with x = 0 or 1, using the Clausius-Mosotti relation. Two new blue laser systems, constituted of a laser crystal and a non-linear crystal optimized for type-I NCPM second harmonic generation, were achieved: a 946 nm Nd:YAG laser with Gd0.87Y0.13COB and a 900 nm Nd:ASL laser with Gd0.56Y0.44COB. Moreover, we have performed for the first time a CW laser action at 900 nm with Nd:ASL. (author)