Photonic nanojet induced modes generated by a chain of dielectric microdisks

High intensity and low divergence photonic nanojet-induced modes are observed in a chain of dielectric microdisks illuminated from the side with laser source of wavelengths 405 nm, 532 nm, and 671 nm. The properties of transmission in a chain of dielectric microdisks are calculated by using finite-difference time-domain method. The spectra of propagation lightwave within the chains of SiO₂ and Si₃N₄ microdisks are directly measured by a scanning optical microscope system with an optical-fiber probe. The photonic nanojet-induced modes are observed from the optical microscope images for the 3 μm, 5 μm, and 8 μm microdisk chains on a silicon substrate. The incident lightwave can be periodically reproduced in chains of dielectric microdisks due to photonic nanojets. The theoretical and experimental results on the field-of-view, transmission, and scattering loss are reported. Understanding these nanojet-induced modes is critical for selecting suitable microdisks to construct optical waveguides and photonic circuits for efficient lightwave guiding.