Physical review. B, Condensed matter
Stimulated emission of 0.2-THz phonons in La F3 : Er3+
D. J. Sox, John E. Rives, Richard S. Meltzer
Abstract
Stimulated emission of phonons in the 0.2-THz frequency range is observed in La${\mathrm{F}}_{3}$:${\mathrm{Er}}^{3+}$. The phonons are generated in the relaxation between the Kramers components of the $^{4}S_{\frac{3}{2}}(1)$ state of ${\mathrm{Er}}^{3+}$ split in a magnetic field after inverting the population with a pulsed tunable dye laser. The stimulated emission is identified from the temporal behavior of the luminescence from the upper Kramers component which shows a speedup in the relaxation during inversion. The population dynamics are analyzed with the rate equations for the system. Comparison with experiment indicates strong preferential stimulated emission along the axis of the cylindrically excited volume and a gain of up to 5 ${\mathrm{mm}}^{\ensuremath{-}1}$. The population inversion exists sufficiently long for phonon propagation over macroscopic distances and the phonon frequency is tunable with the magnetic field.