Liquid Droplet Microresonators

Sensors

Paolo De Natale¹  Pietro Malara²  Saverio Avino²  Gianluca Gagliardi²  Antonio Giorgini² 

[1] Consiglio Nazionale delle Ricerche, Istituto Nazionale di Ottica (INO), Largo E. Fermi 6—50125 Firenze, Italy;Consiglio Nazionale delle Ricerche, Istituto Nazionale di Ottica (INO), via Campi Flegrei 34—Comprensorio A. Olivetti, 80078 Pozzuoli (Na), Italy;

关键词: whispering gallery modes;    droplet micro-cavity;    free-space laser excitation;    optical Q-factor;    cavity ring-down spectroscopy;    cavity optomechanics;   

DOI  :  10.3390/s19030473

来源: DOAJ

【 摘 要 】

We provide here an overview of passive optical micro-cavities made of droplets in the liquid phase. We focus on resonators that are naturally created and suspended under gravity thanks to interfacial forces, illustrating simple ways to excite whispering-gallery modes in various slow-evaporation liquids using free-space optics. Similar to solid resonators, frequency locking of near-infrared and visible lasers to resonant modes is performed exploiting either phase-sensitive detection of the leakage cavity field or multiple interference between whispering-gallery modes in the scattered light. As opposed to conventional micro-cavity sensors, each droplet acts simultaneously as the sensor and the sample, whereby the internal light can detect dissolved compounds and particles. Optical quality factors up to 107⁻108 are observed in liquid-polymer droplets through photon lifetime measurements. First attempts in using single water droplets are also reported. These achievements point out their huge potential for direct spectroscopy and bio-chemical sensing in liquid environments. Finally, the first experiments of cavity optomechanics with surface acoustic waves in nanolitre droplets are presented. The possibility to perform studies of viscous-elastic properties points to a new paradigm: a droplet device as an opto-fluid-mechanics laboratory on table-top scale under controlled environmental conditions.

【 授权许可】

Unknown