Whispering-Gallery Mode Resonators for Liquid Droplet Detection

Whispering-gallery mode (WGM) dielectric resonators provide compact design, high mechanical stability and high quality factors from microwaves up to frequencies in the visible range. In particular, the specific dielectric response of liquids in micro- and (sub)millimetre wave frequency bands (10 GHz to 3 THz) make WGM mode resonators and resonator arrays in this frequency range attractive for highly sensitive liquid detection and identification of small droplets down to volumes of picolitres. Since droplets are usually generated by computer controlled microinjection pipettes being moved on a 2D scanning table, free access to the sensitive resonator surface from above is essential.