Researchers have fabricated a fiber-based Fabry-Perot microcavity containing a pair of mechanically coupled membranes built by 3D direct laser writing — a technique that allows the membrane geometry and spacing to be tuned far more freely than conventional fabrication routes permit. The work, posted as an unreviewed preprint on arXiv, targets a long-standing challenge in cavity optomechanics: realizing multi-membrane "membrane-in-the-middle" systems whose collective motion couples more strongly to light than any single membrane alone.
The authors report mechanical mode hybridization between the two membranes with coupling rates reaching Jmech/2π = 0.16 MHz, a value they say exceeds the individual mechanical linewidths — the condition needed for the modes to be considered strongly coupled. For the collective breathing mode of the membrane stack, they measure an optomechanical coupling strength of gcol(−)/2π ≈ 0.1 MHz. Transfer-matrix simulations presented in the paper suggest that reducing membrane thickness and spacing, or adding more membranes, could yield substantially larger enhancements.
The central claim is that direct laser writing offers a scalable, geometrically flexible route to multi-membrane optomechanical arrays — sidestepping the alignment and fabrication constraints that have limited previous two-membrane experiments. Because this is a preprint that has not yet undergone peer review, the results and their interpretation should be treated as preliminary until independently evaluated.