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Surface Plasmon Resonance and THz Radiation
Published in Hitendra K. Malik, Laser-Matter Interaction for Radiation and Energy, 2021
This cannot be true for plane waves for any angle of incidence. Therefore, plane wave cannot be used directly to excite the surface plasmons. Hence, the surface plasmons are excited through the evanescent waves generated. Thus, a prism is kept near the metal interface and a wave is allowed to incident on it so that the total internal reflection takes place at the bottom surface of the prism due to which evanescent wave is produced parallel to the metal surface. As the angle of the incidence is varied, the wave vector of the evanescent wave changes. At a certain angle of incidence, it matches with that of the surface plasmon, and significant energy transfer takes place and the dip is observed in the reflected light. This is how the surface plasmons are excited.
Sharp focusing of light with microoptics components
Published in V. A. Soifer, Diffractive Optics and Nanophotonics, 2017
As part of the study of the objects we carried out focusing in the near fi eld where there are evanescent waves, and for the experimental verification of the results we used scanning near‐field optical microscopy (SNOM), enabling the detection of evanescent waves. The SNOM concept is to use probes which, being in close proximity to the sample surface, are able to transform the evanescent wave to a propagating one. The first scanning near‐field microscope was designed in 1984 by Dieter Pohl and his colleagues [33]. Thus, the fi rst SNOM was created only two years later aft er the construction of the scanning tunneling microscope—the first probe microscope [34]. In our studies used a Ntegra Spectra (NT‐MDT) microscope, its image and the optical scheme of the experiments are shown in Fig. 3.5.
Microscale Radiative Heat Transfer
Published in C. B. Sobhan, G. P. Peterson, Microscale and Nanoscale Heat Transfer, 2008
Photon tunneling phenomenon is due to the interaction of evanescent waves in gaps smaller than the wavelength of the emitting source. Evanescent waves are exponentially decaying electromagnetic waves in space. Tunneling has found widespread use in applications such as optical microscopy and microscale thermophotovoltaic devices. Fu et al. (2007) theoretically analyzed the energy transmission by photon tunneling in multilayer structures, including negative refractive index materials. (Negative refractive index materials were first proposed as hypothetical materials (Veselago 1968). These have peculiar properties such as the focusing of light by a flat slab. The analysis presented in the paper predicted transmittance spectra in the multilayer structures, and examined the influence of the number of layers on the transmittance.
Surface plasmon resonance sensor for refractive index and temperature measurement based upon a double-sided polished microstructured fiber
Published in Instrumentation Science & Technology, 2023
Xin Yan, Yang Zhao, Tonglei Cheng, Rao Fu
The reported structure is simple and easy to prepare. A schematic is shown in Figure 3b. When light enters the fiber, it travels into its silica layer. Since the outer layer of silica is coated with a thin metal film, light leaks into the cladding. These cladding waves are affected by the surrounding medium at the boundary of the cladding. Due to total reflection, evanescent waves are generated at the interface between the cladding and the metal film. When the evanescent wave and the surface plasmon wave are equal, the surface plasmons are resonantly excited, resulting in a portion of the energy of the incident light being transferred to the metal film and the reflected light energy is reduced. The optical power received by the spectrometer decreases and a dip is created in the spectrum. This resonance dip shifts due to the changes in the refractive index of the surrounding medium. Thus, sensing is achieved by observing the change in the resonant wavelength.
Time reversal mirror for hyperthermia of multi-focal breast tumors using electromagnetic time reversal technique
Published in Electromagnetics, 2022
Baidenger Agyekum Twumasi, Jia-Lin Li, Ebenezer Tawiah Ashong, Christian Dzah, Dustin Pomary
It has been established that sub-wavelength information about an object is carried by evanescent waves, but these waves decay exponentially. This implies that these waves are lost before reaching the far-field image plane which is the origin of the diffraction limit. In near-field microscopy, one such approach for the recovery of evanescent waves is the loading of sub-wavelength scatterers in the near field of the object to be imaged. Evanescent waves can be converted into propagating waves by diffracting off these scatterers which enables their detection or reception in the far-field by the time reversal mirror (Lerosey et al. 2007). This idea is extended to the hyperthermia of multi-focal breast tumors. In time reversal application, a single antenna TRM can be used and this will act as a transmitter and at the same time as a receiver of the field. But for the proposed application, we used five antenna TRMs, where one is placed below the breast and loaded with the SRESP scatterers. This antenna is excited to send out the probing signal (channel sounding). The other four TRMs surrounding the breast act as receivers during the first phase of the time reversal process. During the second phase after the received and recorded signals (field) has been flipped in time, the four antenna TRMs then transmit these signals back into the breast medium for the spatial-temporal focusing at tumor locations. The procedure can be outlined as follows (Ge et al. 2011):
Theoretical investigation of the effect of the geometry on the sensitivity of tapered-fiber sensors based on staircase concatenation method
Published in Journal of Modern Optics, 2022
Optical fibers have been widely studied owing to their applications such as communications, sensing, and fabrication of fibre lasers and devices demonstrating nonlinear effects. They are immune to electromagnetic noise and possess lightweight, low transmission loss in the communication window and large bandwidth. In recent decades, several fibre optical sensors have been designed and examined for various applications [1–4]. Tapered optical fibre (TOF) sensors have been recently attracted significant attention from researchers [5–11]. By tapering the fibre, the evanescent field extends out of the fibre surface and interacts with the surrounding material. The evanescent interaction of the guided wave with the surrounding media would be a powerful tool for sensing applications.