Nd : Y2O3 single-crystal fiber laser: Room-temperature cw operation at 1.07- and 1.35-μm wavelength

Abstract

Single‐crystal fibers have been grown from high‐purity 1.5 wt% Nd₂O₃ : Y₂O₃ powder mixtures, and short lengths of the fiber in dielectric mirror resonators have been evaluated as lasers at both 1.07‐ and 1.35‐μm wavelength. The laser transition cross sections were approximately equal at the two wavelengths, and they were about two‐thirds the cross section of Nd : YAG at 1.31 μm. The fluorescence lifetime of the laser samples was 340 μsec. Loss in the material was approximately 3% per cm. The absorption spectrum from 0.7 to 1.0 μm and fluorescence spectra for the 4F_3/2→4I_9/2, 4F_3/2→4I_11/2, and 4F_3/2→4I_13/2 manifolds of Nd³⁺ in Y₂O₃, taken with fiber samples, are reproduced in detail. The resultant energy levels are given. With a Kr laser operating at 0.7525 μm as the end pump, minimum observed laser threshold was 0.57 mW absorbed pump power for a 100‐μm‐diam 2.5‐mm‐long fiber operating cw in room‐temperature air at 1.07 μm. The lasers operated in one or two transverse modes and had active linewidths of approximately 2 Å.