Slow light and slow acoustic phonons in optophononic resonators

Slow light has been exploited in optoelectronics to enhance the light-matter interaction, including light absorption and emission, nonlinear processes such as sum-frequency generation and phase modulation, and lasing. Modulated structures that modify the propagation of light can also be tailored to alter the propagation of sound. The question then arises: how can slow high-frequency acoustic waves and slow light in the same device perform with a perspective in optomechanics? This question becomes particularly relevant in view of recent reports of photon lifetimes extended to the millisecond range (lifetimes that are characteristic of phonons) by introducing slow-light effects in microresonators. With this application in mind, this work studies DBR-based GaAs/AlAs microcavities as structures that present both light confinement and slowing-down, depending on whether the laser is tuned resonantly to the cavity or stop-band edge modes. Interestingly, the authors show that for these kind of devices precisely the same happens for acoustic phonons, thus providing a rich playground to investigate confined and slow optomechanical effects. Time-resolved coherent phonon generation experiments using picosecond lasers are reported, showing a strong enhancement of the optomechanical coupling using both confined and also properly designed slow photon and phonon modes. The prospects for the use of these optoelectronic devices in confined and slow optomechanics is addressed.