The study of levitated nanoparticles recently gained tremendous interest for its potential application in high precision sensing and quantum information science. One of the eld's challenges is to increase
the particle light coupling while maintaining good optical access for trapping beams. Here we propose a mesoscopic cavity device that closes a technical gap between ber-based microcavities and conventional
glass substrate cavities. The device enables cutting-edge research with levitated nanoparticles and trapped ions: For the rst time, both species can be coupled to an integrated single mode, small mode
volume cavity with good optical access. The mesoscopic cavity will be implemented in the Novotny group for experiments with levitated nanoparticles. We envision specic applications for quantum limited
sensing and transduction. In this context we foresee a high impact of the device for other modern quantum experiments.