Broadband Mie scattering from optically levitated aerosol droplets using a white LED.
We describe a simple and efficient means of using a white LED source to illuminate an optically levitated aerosol droplet to enable study of broadband Mie scattering. The backscattered resonances are imaged through a spectrograph and CCD which show high resolution Mie scattering intensity distributions across a spectral range of 480 to 700 nm. The wide spectral range allows assignment of resonance mode numbers and mode orders using conventional Mie theory calculations. Accurate droplet sizing, within +/- 2 nm, is possible for water-based droplets with radii between 2 microm and 8 microm. We additionally demonstrate that the refractive index dispersion can be determined from a single refractive index value at known wavelength. Finally, morphological droplet dynamics are presented showing non-linear droplet evaporation behaviour at a temporal resolution of 100 milliseconds.
Central Laser Facility, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot, UK. a.d.ward@rl.ac.uk
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Ward
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Zhang
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Hunt
D000336:Aerosols / Q000737:chemistry*; D004867:Equipment Design / Q000379:methods*; D019544:Equipment Failure Analysis; D008027:Light; D008029:Lighting / Q000295:instrumentation* / Q000379:methods; D010783:Photometry / Q000295:instrumentation* / Q000379:methods; D012031:Refractometry / Q000295:instrumentation*; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012666:Semiconductors; D012680:Sensitivity and Specificity
D000336:Aerosols