A quasi-droplet optofluidic ring resonator laser using a micro-bubble

Abstract

Optofluidic ring resonator lasers based on micro-bubbles filled with liquid gain medium are demonstrated. Due to the sub-micron wall thickness of the micro-bubble, significant amount of the electric field resides inside the liquid. Consequently, micro-bubbles mimic the droplets in air that have 3-dimensional optical confinement, extremely high Q-factors, and versatility in handling liquids of different refractive index. Furthermore, they enable repetitive interrogation and easy directional laser emission out-coupling without evaporation or size/shape variations. The laser using Rhodamine 6G in methanol is achieved with a threshold of 300 nJ/mm2 and 5.3 μJ/mm2 for 1 mM and 10 μM in concentration, respectively.

Brillouin cavity optomechanics with microfluidic devices

“…These results are, therefore, a step towards novel experiments probing optomechanics on non-solid phases of matter. In particular, the high frequency, high quality-factor mechanical modes demonstrated in this work may enable strongly localized, high-sensitivity, optomechanical interaction with chemical and biological analytes 36,37 as environmental parameters like pressure and cell nutrients are relatively easy to control inside the hollow resonator 32,38,39 , and as the liquid volume within the device is the scale of a living cell.…”

“…However, as we can fabricate the resonator with walls as thin as 560 nm (ref. 32) we believe that a large acoustic penetration to water will be possible in such thin-wall silica bubble resonators even for the 11 GHz mode (ME650), which can open a rare hypersonic window for the acoustic analysis of liquids. Reduction in wall thickness may even allow access to an interesting regime where giant-enhanced Brillouin scattering is predicted 33 .…”

Cavity optomechanics on a microfluidic resonator with water and viscous liquids

“…We can fabricate devices with various bubble diameters upon request and with wall thickness below 600 nm. 8 Experimental set-up We evanescently couple light from a tapered optical fibre 19 (Figure 1d and 1e) into the glass bubble to excite its optical whispering-gallery Water is inserted in the bubble through a microcapillary inlet, using a syringe pump. The optical wavelength that we used is 1.5 mm.…”

“…Bubbles along microcapillaries 7,8,16,17 and on-chip 18 devices can possess excellent optical transmission 7,8,16,17 together with low mechanical dissipation while allowing liquid to be placed inside the device. Additionally, such glass bubbles can benefit from optically excited vibrations as no electrodes are needed.…”

“…5,6 Just like we use more than one sense (e.g., eyes and ears) to detect hazards, optomechanics might suggest a bridge between the seemingly parallel optical and mechanical detection fields. The recent availability of liquid containing bubble shaped resonators, 7,8 in combination with optomechanical vibrations at .GHz rate, 9-12 might pave the way for ultrasound investigations on analytes in liquids. Nevertheless, cavity optomechanics on non-solid phases of material was never before demonstrated.…”