Optical control over multi-membrane materials

Acoustic metamaterials and circuits allow to shape and control the propagation of vibrations, i.e., phonons, in an artificial material. Using the interaction of phonons with light in so called optomechanical devices, single material sites can be interfaced and mechanical properties be locally tuned. Optomechanically controlled acoustic circuits hold great promise for a wide range of applications from routing and manipulation of vibrations in integrated acoustic circuits, over topological optomechanical materials and non-reciprocal devices, to optomechanical arrays. So far, optomechanical control of acoustic metamaterials on the scale of only up to two interface sites has been achieved by optomechanical crystals or coupled microdisks. The limited access to interface sites and the dominating disorder in those systems poses fundamental restrictions on the size, complexity, and amount of control over the acoustic layer.My project will realize a new platform for optically interfaced, integrated acoustic circuits that lifts the present restrictions. To this end, I will interface InGaP-membrane resonator arrays, i.e., the acoustic metamaterial, fabricated over a distributed Bragg reflector (DBR) substrate using flexibly positioned micromirrors on optical fiber tips. This system establishes an out-of-plane optical interface using a membrane-in-the-middle cavity scheme. The microscopic Fabry-Perot cavity approach enables large optomechanical spring effects that are used to individually control the acoustic material sites and that surpass both disorder and the direct mechanical coupling of acoustic resonator sites. This novel approach will allow for an unprecedented and hitherto unachieved level of optical control over acoustic metamaterials.The platform established within this project will be suited for a vast number of applications complementing other integrated device platforms and opening a pathway to concepts so far only studied in theoretical proposals.