High-precision spectral tuning of micro and nanophotonic cavities by resonantly enhanced photoelectrochemical etching

We present a simple method to tune optical micro- and nanocavities with picometer precision in the resonant wavelength, corresponding to an effective sub atomic monolayer control of the cavity dimension. This is obtained through resonant photo-electrochemical etching, with in-situ monitoring of the optical spectrum. We employ this technique to spectrally align an ensemble of resonant cavities in a permanent manner, overcoming the dimension variability resulting from current nanofabrication techniques. In a device containing several resonators, each is individually addressed and tuned, with no optical quality factor degradation. The technique is general and opens the way to multiple applications, such as the straightforward fabrication of networks of identical coupled resonators, or the tuning of chip-based cavities to external references.