ABSTRACT
Many diverse technological applications, such as soft robotics and flexible electronics, demand the development of intelligent sensors that can simultaneously detect different physical parameters. Taking advantage of plasmonic structures, which can experience minute variations in physical parameters upon close contact, herein, a dual channel based silver nanostructure of concentric square rings and disks on an SiO2 substrate is proposed for the synchronized detection of magnetic field (H) and temperature (T). The thermometric polydimethylsiloxane (PDMS) and ferromagnetic Fe3O4 were placed in two channels of the nanostructure, forming the sensor. The structure modeling and electromagnetic study were carried out using the finite element method (FEM). The simultaneous detection of H and T was realized through the sensing matrix, which solved the problem of cross-sensitivity caused by a variation in temperature. Furthermore, the impact of structural asymmetry on the performance of the sensor was studied by tuning its geometrical parameters, such as disk length and ring length, separately and together. Asymmetry and the channel size significantly enhanced the performance, where disk optimization increased the temperature and magnetic field sensitivity by about 760 and 8319 times using 70% and 80% asymmetric systems, respectively. Also, the smallest ΔW (5 nm) provided a sufficiently high channel separation factor of about 7.47 µm during multi-parameter sensing. In addition, asymmetric sensing toward a single parameter was tested by placing PDMS/Fe3O4 on both channels. Multiple peaks were displayed with high sensitivity and CH-factor, making the detection more specific. Thus, the system possessing a combination of narrow channels and unique channel asymmetry exhibited excellent multi- and single-sensing for the detection of temperature and magnetic field.
ABSTRACT
We investigate the optical properties of a photonic crystal (PC) composed of a quasi-one-dimensional flat-band lattice array through finite-difference time-domain simulations. The photonic bands contain flat bands (FBs) at specific frequencies, which correspond to compact localized states as a consequence of destructive interference. The FBs are shown to be nondispersive along the Ð â X line, prohibiting optical transmission with incident light in x direction. On the other hand, the photonic band for the FB frequency is found to be dispersive along the Ð â Y line, resulting in nonzero optical transmission. Such anisotropic optical response of the PC due to the FB localization of light in a single direction only results in a self-collimation of light propagation throughout the PC at the FB frequency.
ABSTRACT
Flatband systems typically host "compact localized states" (CLS) due to destructive interference and macroscopic degeneracy of Bloch wave functions associated with a dispersionless energy band. Using a photonic Lieb lattice (LL), such conventional localized flatband states are found to be inherently incomplete, with the missing modes manifested as extended line states that form noncontractible loops winding around the entire lattice. Experimentally, we develop a continuous-wave laser writing technique to establish a finite-sized photonic LL with specially tailored boundaries and, thereby, directly observe the unusually extended flatband line states. Such unconventional line states cannot be expressed as a linear combination of the previously observed boundary-independent bulk CLS but rather arise from the nontrivial real-space topology. The robustness of the line states to imperfect excitation conditions is discussed, and their potential applications are illustrated.
