Doppler amplification of motion of a trapped three-level ion

The system of a trapped ion translationally excited by a blue-detuned near-resonant laser, sometimes described as an instance of a phonon laser, has recently received attention as interesting in its own right and for its application to non-destructive readout of internal states of non-fluorescing ions. Previous theoretical work has been limited to cases of two-level ions. Here, we perform simulations to study the dynamics of a phonon laser involving the Λ-type ¹³⁸Ba + ion, in which coherent population trapping (CPT) effects lead to different behavior than in the previously studied cases. We explore optimization of the laser parameters to maximize amplification gain for initially seeded motion and consider the related signal-to-noise ratios for internal state readout. We find that good Doppler amplification and state readout performance can be obtained even when operating quite near the CPT dip.