Circularly polarized luminescence (CPL) spectroscopy is an analytical technique that detects the difference in luminescence intensity between left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) light during optical excitation of a sample (Figure 1). Recent years have seen an increased amount of research on compounds exhibiting CPL properties, because such compounds are expected to find applications in next-generation display fields including 3D displays, life science fields such as optical sensing and bioimaging, and security fields including communication technology and anti-counterfeiting technology.

Fig. 1 Schematic diagram of CPL measurement

Generally, the CPL intensity is expressed using the luminescence dissymmetry factor (g_lum), which is defined by the following equation (Figure 2).

Here, I_L and I_R represent the luminescence intensities of LCP light and RCP light, respectively. Generally, g_lum is between −2 and 2, with −2 representing pure RCP light and +2 representing pure LCP light.

Fig. 2  Relative luminescence intensity for LCP (blue) and RCP (red) light, together with definition of g_lum