Determining Pasteur Parameter for Chiral Medium using Long-Range Surface Plasmon Resonance

Chirality is a fundamental property of nature, and recognizing chirality is crucial for human life. In this paper, a theoretical study on highly sensitive determination of the Pasteur parameter in chiral measurement is presented using long-range surface plasmon polariton (LRSPP) resonance. The method is based on a thorough analysis of electromagnetic wave propagating in multilayer planar waveguide structures containing a chiral medium. Both the handedness and magnitude can be determined simultaneously, either by measuring the relative direction and separation of the spectral shift of the reflected right- and left-handed circularly polarized components under the condition of an excited “bright” LRSPP mode, or by detecting the relative direction and amount of intensity split in the region of a “dark” LRSPP mode. The method offers improved measurement of the Pasteur parameter of 10⁻³ level for the “bright” mode and allows for an ultrasensitive measurement of 10⁻⁵ level for the “dark” mode. It is also immune to spectrum fluctuations or drifts caused by variations in the host refractive index or absorption loss. It is hoped that this work will inspire further optical techniques for high-sensitivity chiral sensing and detection.