Twisting laser light offers the chance to probe the nano-scale

A new method to sensitively measure the structure of molecules has been demonstrated by twisting laser light and aiming it at miniscule gold gratings to separate out wavelengths.

The technique could potentially be used to probe the structure and purity of molecules in pharmaceuticals, agrochemicals, foods and other important products more easily and cheaply than existing methods.

Developed by physicists at the University of Bath, working with colleagues at the University of Cambridge and University College London, the technique relies on the curious fact that many biological and pharmaceutical molecules can be either ‘left-handed’ or ‘right-handed’.
Although such molecules are built from exactly the same elements they can be arranged in mirror images of each other, and this configuration sometimes changes their properties drastically.

Notoriously the morning sickness drug Thalidomide caused birth defects and deaths in babies before it was pulled from the market in the 1960s. Investigation showed that the drug existed in two mirror images – the right-handed form was effective as a morning sickness drug, but the left-handed form was harmful to foetuses. This is one example of why testing what ‘handedness’, or chirality, a molecule has is essential for many valuable products.

The research team from the Centre for Photonics and Photonic Materials, and the Centre for Nanoscience and Nanotechnology at the University of Bath, used a special white-light laser built in-house and directed it through several optical components to put a twist on the beam. The twisted laser beam then hits a nano-scopic U-shaped gold grating which serves as a template for the light, further twisting the beam in either a right or left-handed direction. This deflects the beam in many directions and further splits it into its constituent wavelengths across the colour spectrum.


Image Credit:  Ventsislav Valev

Recent News