Optical chirality

Chiral objects interact asymmetrically with chiral fields. For example, a chiral molecule is excited at slightly different rates when exposed to left- or right-circularly polarized light (CPL), an effect called circular dichroism. Circular dichroism (CD) is widely used to characterize organic and biological compounds.

Chiroptical effects are typically very small, because the wavelength of light is so much larger than the size of most molecules. The electromagnetic field undergoes a nearly imperceptible twist over molecular dimensions.

To couple more strongly to molecular chirality, one should increase the chirality, or twistiness, of the electromagnetic field. We invented a quantity, optical chirality, that quantifies the degree of chiral dissymmetry in electromagnetic fields. We further showed how one could engineer electromagnetic fields to maximize the chiral dissymmetry.


Trapping single molecules in solution

The Anti-Brownian ELectrokinetic trap (ABEL trap) is a device for trapping and manipulating single molecules in solution at room temperature. It couples fluorescence microscopy to real-time electrokinetic feedback to control the motion of individual molecules. By actively canceling a molecule's Brownian motion, individual free-floating molecules can be observed for extended times. The ABEL trap has been used to trap and study fluorescent quantum dots, molecules of DNA, fluorescently labeled lipid vesicles, single virus particles, single proteins, and even single dye molecules.



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