  Coherent acoustic phonon generation and detection assisted by optical
resonances are at the core of efficient optophononic transduction processes.
However, when dealing with a single optical resonance, the optimum generation
and detection conditions take place at different laser wavelengths, i.e.
different detunings from the cavity mode. In this work, we theoretically
propose and experimentally demonstrate the use of elliptical micropillars to
reach these conditions simultaneously at a single wavelength. Elliptical
micropillar optophononic resonators present two optical modes with orthogonal
polarizations at different wavelengths. By employing a cross-polarized scheme
pump-probe experiment, we exploit the mode splitting and couple the pump beam
to one mode while the probe is detuned from the other one. In this way, at a
particular micropillar ellipticity, both phonon generation and detection
processes are enhanced. We report an enhancement of a factor of ~3.1 when
comparing the signals from elliptical and circular micropillars. Our findings
constitute a step forward in tailoring the light-matter interaction for more
efficient ultrahigh-frequency optophononic devices.
