Extraordinary optical transmission from a thin microcavity by macroscopic quantum effect

The macroscopic quantum effect is revealed to elaborate the extraordinary optical transmission (EOT) from a subwavelength thin microcavity based on the uncertainty property of the transmitted electromagnetic fields after the aperture. A critical radius is found in the thin microcavity under a certain incident electromagnetic wavelength. With the aperture radius varying, the transmitted field can be divided into three regimes: I. the macroscopic quantum regime when the aperture radius is less than the critical radius, in which the field edge effect occurs and EOT phenomenon is perfectly manifested; II. The wave-particle duality regime in the vicinity of the critical radius, in which the edge effect and diffraction phenomenon exist simultaneously; III. The wave regime when the aperture radius is greater than the critical radius, in which the near-field diffraction emerges. In addition, the influences of incident wavelength and microcavity thickness on EOT are also investigated. Our research have potential applications in advanced optical devices, such as light switch and optical manipulations.

Extraordinary optical transmission in silicon nanoholes

In this work, for the first time, a study was conducted of the existence of Extraordinary Optical Transmission (EOT) in Silicon (Si) thin films with subwavelength holes array and high excess carrier concentration. Typically EOT is studied in opaque perforated metal films. Using Si would bring EOT and its many applications to the silicon photonics realm and the mid-IR range. Since Si thin film is a semi-transparent film in mid-IR, a generalization was proposed of the normalized transmission metric used in literature for EOT studies in opaque films. The plasma dispersion effect was introduced into the studied perforated Si film through either doping or carriers’ generation. Careful consideration for the differences in optical response modeling in both cases was given. Full-wave simulation and analysis showed an enhanced transmission when using Si with excess carriers, mimicking the enhancement reported in perforated metallic films. EOT was found in the mid-IR instead of the visible range which is the case in metallic films. The case of Si with generated excess carriers showed a mid-IR EOT peak reaching 157% around 6.68 µm, while the phosphorus-doped Si case showed a transmission enhancement of 152% around 8.6 µm. The effect of varying the holes’ dimensions and generated carriers’ concentration on the transmission was studied. The analogy of the relation between the fundamental mode cutoff and the EOT peak wavelength in the case of Si to the case of metal such as silver was studied and verified. The perforated Si thin film transmission sensitivity for a change in the refractive index of the holes and surroundings material was investigated. Also, a study of the device potential in sensing the hole and surroundings materials that have almost the same refractive index yet with different absorption fingerprints was performed as well.

A Theoretical Study of Broadband Extraordinary Optical Transmission in Gold Plasmonic Square Nanohole Arrays and its Application on Refractive Index Sensor

Extraordinary optical transmission (EOT) behaviour is investigated in a subwavelength plasmonic nanostructure, consisting of a gold film perforated with a square nanohole array and deposited on a silicon dioxide substrate. The essential aspect of the proposed structure is the periodic disorder that enables broadband transmission peaks in the visible and near-infrared region and reduces the structure's size, which mainly arises from the excitation of localized surface plasmon resonances (LSPRs). Optical cavity modes formed in the nanoholes and the hybridization of plasmon modes. Further, the performance of the proposed nanostructure as a plasmonic sensor is analyzed by increasing the index of refraction of the local environment; the EOT exhibit remarkable refractive index sensitivity of up to 944 nm/RIU, a figure of merit of 9.25 and a contrast ratio of 47% are realized. The proposed structure has some practical significance for designing low-cost and effective sensing devices.

Extraordinary Optical Transmission by Hybrid Phonon–Plasmon Polaritons Using hBN Embedded in Plasmonic Nanoslits

Hexagonal boron nitride (hBN) exhibits natural hyperbolic dispersion in the infrared (IR) wavelength spectrum. In particular, the hybridization of its hyperbolic phonon polaritons (HPPs) and surface plasmon resonances (SPRs) induced by metallic nanostructures is expected to serve as a new platform for novel light manipulation. In this study, the transmission properties of embedded hBN in metallic one-dimensional (1D) nanoslits were theoretically investigated using a rigorous coupled wave analysis method. Extraordinary optical transmission (EOT) was observed in the type-II Reststrahlen band, which was attributed to the hybridization of HPPs in hBN and SPRs in 1D nanoslits. The calculated electric field distributions indicated that the unique Fabry–Pérot-like resonance was induced by the hybridization of HPPs and SPRs in an embedded hBN cavity. The trajectory of the confined light was a zigzag owing to the hyperbolicity of hBN, and its resonance number depended primarily on the aspect ratio of the 1D nanoslit. Such an EOT is also independent of the slit width and incident angle of light. These findings can not only assist in the development of improved strategies for the extreme confinement of IR light but may also be applied to ultrathin optical filters, advanced photodetectors, and optical devices.

Modelling 1-D Copper Grating for Extraordinary Optical Transmission

The excitation of surface plasmon polaritons (SPPs) and its association with extraordinary optical transmission (EOT) has been presented in this report.. The 1-dimensional periodic grating structure of copper (Cu) has been designed over the glass substrate in rf-module of COMSOL Multiphysics 5.3a. The geometry was illuminated from glass side with visible-near infrared (400-900nm) electromagnetic spectrum. The 0th order transmission spectra have been investigated to study the maximum value of EOT at different slit widths by taking the period (700nm) and thickness of Cu grating (50nm) constant. Moreover, the near field analysis has been used to investigate the field behavior at desired interface and to verify the results of transmission spectra. It is worth mentioning that the highest value of EOT corresponds to the slit width of 250nm which is affiliated with the strongest plasmonic mode i.e., fundamental plasmonic mode. Such devices are increasingly applicable in sensing, chemical and solar cell industries.