Determination of Enantiomeric Excess by Optofluidic Microlaser near Exceptional Point.

Enantiomeric excess (ee) is an essential indicator of chiral drug purification in the pharmaceutical industry. However, to date the ee determination of unknown concentration enantiomers generally involves two separate techniques for chirality and concentration measurement. Here, a whispering-gallery mode (WGM) based optofluidic microlaser near exceptional point to achieve the ee determination under unknown concentration with a single technique is proposed. Exceptional point induces the unidirectional WGM lasing, providing the optofluidic microlaser with the novel capability to measure chirality by polarization, in addition to wavelength-based concentration detection. The dual-parameters detection of optofluidic microlaser empowers it to achieve ee determination of various unknown enantiomers without additional concentration measurements, a feat that is challenging to accomplish with other methods. Featuring the sensitivity enhancement and miniature structure of the WGM sensors, the obtained chiroptical response of the present approach is ≈30-fold higher than that of the conventional optical rotation-based polarimeter, and the reagent consumption is reduced by three orders of magnitude.