Control and characterisation of a single aerosol droplet in a single-beam gradient-force optical trap

Optical tweezers are used to control aerosol droplets, 4-14 mum in diameter, over time frames of hours at trapping powers of less than 10 mW. When coupled with cavity enhanced Raman scattering (CERS), the evolution of the size of a single droplet can be examined with nanometre accuracy. Trapping efficiencies for water and decane droplets are reported and the possible impact of droplet heating is discussed. We demonstrate that the unique combination of optical tweezing and CERS can enable the fundamental factors governing the coagulation of two liquid droplets to be studied.