Switchable Photonic Nanojet by Electro-Switching Nematic Liquid Crystals

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.

All-dielectric concentration of electromagnetic fields at the nanoscale: the role of photonic nanojets

“…LCs have been extensively utilized in many elds including organic electronics and energy conversion, the creation of nanostructured materials or ordering nano-and microparticles, actuators, polymer-dispersed LCs, and spatial light modulators. [69][70][71][72][73] Liu et al, 74 Matsui et al, 75 Eti et al, 76 and Du et al, 77 have investigated the properties of PNJs as functions of the phase transitions of LCs, but the rst experimental imaging of tunable PNJs using LC control appears to have been achieved by Matsui and Tsukuda. 78 In their experiments, a LC microdroplet formed in a polydimethylsiloxane (PDMS) matrix is sandwiched between indium-tin-oxide (ITO) electrodes.…”

“…93 For example, to detect intrinsic nanostructures and articially introduced nanoparticles that are deeply embedded within biological cells researchers requires a long PNJ length, whereas a rapidly convergent PNJ generated by the microsphere or microcylinder is followed by a fast divergence. 77 We give, herein, a review on the major published results of the past decade on the geometry engineering for PNJs, to remind our readers of the diversity in PNJ customization. Geints et al investigated the longitudinal and transverse dimensions of the PNJ as well as the dependence of its peak intensity on the optical contrast of micrometer-sized composite particles consisting of a nucleus and several shells with different refractive indices.…”

“… 93 For example, to detect intrinsic nanostructures and artificially introduced nanoparticles that are deeply embedded within biological cells researchers requires a long PNJ length, whereas a rapidly convergent PNJ generated by the microsphere or microcylinder is followed by a fast divergence. 77 We give, herein, a review on the major published results of the past decade on the geometry engineering for PNJs, to remind our readers of the diversity in PNJ customization.…”

Novel Bilayer Micropyramid Structure Photonic Nanojet for Enhancing a Focused Optical Field

“…The most outstanding characteristics of the PNJ are the subwavelength focusing [ 6 , 7 ], the long focus range [ 8 , 9 ], and being easily integrated with other technologies [ 10 , 11 ], which can bring a wide range of opportunities for the practical application of the PNJ in nanolithography [ 12 , 13 ], nanoscopy [ 14 , 15 ], all-dielectric switching [ 16 , 17 ], optical trapping and manipulation [ 18 , 19 , 20 ], etc.…”

Coated High-Refractive-Index Barium Titanate Glass Microspheres for Optically Trapped Microsphere Super-Resolution Microscopy: A Simulation Study

“…Darafsheh et al realized optical super-resolution imaging by using high-refractive-index barium titanate glass (BTG) microspheres ( n ∼ 1.9-2.1) totally immersed in a liquid environment [8], and they also studied the influence of immersion medium on imaging performance in microsphere-assisted microscopy [9]. This label-free super-resolution imaging technique has attracted many research groups across the world, demonstrating sub-diffraction discerning ability in nanostructure detections and biological observations [10][11][12][13]. The super-resolution mechanism of microsphere-assisted microscopy is still a heated topic [14][15][16].…”