Efficient active media based on Nd3+-activated calcium niobium gallium garnets

A spectroscopic investigation was made of Nd³⁺-activated crystals of calcium niobium gallium (CNGG) and calcium lithium niobium gallium (CLNGG) garnets. The energy parameters of active elements made of these crystals were determined for the first time. The absolute efficiency of a CNGG:Nd³⁺ crystal was 3.5%, higher than the efficiency (2.7%) of a YAG:Nd³⁺ crystal of high optical quality. The average output power obtained at a pulse repetition frequency of 50 Hz for a CLNGG crystal was 40 W and the efficiency was 2.7% for an active element 6 mm in diameter and 80 mm long. A comparison of the lasing characteristics of CNGG:Nd³⁺ and CLNGG:Nd³⁺ crystals revealed a considerable superiority of the latter in respect of several parameters: the damage threshold (which was twice as high), the divergence, and the influence of a thermal lens at high pump powers. Room-temperature lasing of CNGG:Nd³⁺ and CLNGG:Nd³⁺ crystals was observed as a result of the ⁴F_3/2 ← ⁴I_11/2 transition at three wavelengths: 1059.3, 1061.5, and 1066 nm.