Tutorial
Microfluidic Optomechanics and Water-Wave Lasers

Water waves, known scientifically as capillary waves, are familiar to everyone. Recently, our team experimentally demonstrated stimulated amplification of light mediated by capillary waves.¹

Our experimental setup is based on our recent demonstration of continuously pumped microdroplet resonators,² which allowed us to map the droplet’s optical,³ capillary⁴ and acoustic⁵ resonances . Two key enablers facilitate our optocapillary energy exchange: We leveraged the droplet optical finesse to over a million, and we transformed the capillary oscillations from the overdamped to the underdamped regime.⁴

Top (left to right): Optical, capillary and acoustic resonances of droplet micro­cavities. Bottom: Experimental setup for a water-wave laser in which light is coupled to a tweezed microdroplet via a tapered fiber. When pump frequency is tuned to one of the droplet resonances, coherent capillary oscillations accompanied by Stokes emission appear above a 77 μW threshold (inset).

1. S. Kaminski et al. Nat. Photon. 10, 758 (2016).

2. S. Kaminski et al. Opt. Express 23, 28914, (2015).

3. S. T. Attar et al. Opt. Express 24, 13134 (2016).

4. S. Maayani et al. Nat. Commun. 7, 10435 (2016).

5. R. Dahan et al. Optica 3, 175 (2016).