Figure 3. The forward scattering RCS of a perfect electric conductor (PEC) nanosphere under different optical wavelengths (color coded) as a function of its diameter.

Based on these RCS values, a detection limit of 250 nm under 532-nm illumination is equivalent to a ~180-nm particle diameter under 266-nm illumination, assuming that the sensor performance and noise levels remain the same. These detection-size limits are significantly improved using self-assembled nanolenses, as illustrated in Fig. 6, enabling the detection of e.g., a ~26 nm particle.