Abstract
This paper first presents a switchable photonic nanojet (PNJ) generated by a polystyrene (PS) microsphere immersed in nematic liquid crystals (NLCs). The PNJ is switched by applying external voltage, which originates from the refractive index change in the surrounding medium caused by the field-induced realignment of liquid crystal molecules. By tuning the refractive index of NLCs larger or smaller than that of the PS microsphere, the PNJ can be switched off or on. Moreover, we present an optimization study to seek a better electric energy focusing property of the PNJ. Our results reveal that the switchability of PNJ can be optimized by applying a shorter incident wavelength, a double-layer microsphere, and a PS ellipsoid. The full width at half-maximum (FWHM) generated by the PS ellipsoid is narrower than that generated by the microsphere with a shorter incident wavelength. The intensity contrast of the PS ellipsoid is higher than that of the double-layer microsphere. As a whole, the switchability of PNJ can be best optimized by a PS ellipsoid. This should open the way for the development of integrated photonic devices.
Highlights
Sub-wavelength optical resolution has become essential for various applications, from optical microscopy [1], lithography [2], and spectroscopy [3], to data storage [4]
A switchable photonic nanojet achieved by a PS microsphere with nematic liquid crystals (NLCs) immersed
The effective refractive index of NLCs canby beachanged by tuning alignment of is reported
Summary
Sub-wavelength optical resolution has become essential for various applications, from optical microscopy [1], lithography [2], and spectroscopy [3], to data storage [4]. The most striking and distinctive feature of PNJ is the high spatial localization of light field in the transverse direction (relative to the direction of incidence), which, in contrast to the conventional high-NA (numerical aperture) focusing optics, can lead to super-resolution dimensions. The maximum intensity of the PNJ can reach several hundred times compared to that of the incident light. These features bring about the potential applications of PNJ for nanoscale processing of materials [22], high-resolution microscopy [23], localized sensing techniques [24], optical data storage [25], optical antennas [26], and so on
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