No abstract

No abstract

We demonstrate a simple way of building a compact eye-safe laser source based on a double-pass pumped extracavity optical parametric oscillator (EOPO) without an optical Faraday isolator. A Nd:KGW pump laser (PL) and the KTP EOPO located close to the PL are designed with stable cavities, while the 100% end system mirrors form an unstable cavity with sufficiently high threshold at 1067 nm. At the 6.6 J pump of the Nd:KGW laser, the EOPO output energy obtained at 1577 nm is 14.7 mJ, corresponding to the conversion efficiency of 33% with respect to the fundamental. The pulse width is 7 ns and the output beam divergence is 3 times diffraction limit.

The Salmi batholith’s successive felsic rocks differentiates are represented by a series: biotite-amphibole granite-rapakivi, biotite granite, highly differentiated granites (Li-siderophyllite granite and zinnwaldite Li-F granite). In this series of rocks a gradual increase in content of Ta and Nb and a decrease in the Nb/Ta ratio is seen. A regular change in the separation factors of Ta and Nb between mica and the total composition of the rock is observed as well. When comparing Li-siderophyllite granites and Li-F granites, the latter have a sharp decrease in the separation coefficients KrTa, Nb. This decrease is due to the fall in content of these metals in Li-F granites zinnwaldite and associated with the appearance of columbite in these rocks. The study of rock samples from the Salmi batholith suggests that the change of the Ta and Nb content in the mica of deeply differentiated granites and the corresponding decrease in the Kr value of these metals may be a diagnostic indication of the presence of columbite mineralization in the rock.