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The Far-Field Superlens
Published in Zhaowei Liu, Plasmonics and Super-Resolution Imaging, 2017
Figure 1.3 shows the layered design of a silver near-field optical superlens for experimental demonstration. A patterned chromium film served as the object. The polymethylmethacrylate (PMMA) layer was a spacer, and photoresist (PR) was placed on the other side of the silver superlens to record the image in the near field. The wavelength used was a common lithographic wavelength. We can clearly see, both in the 2D “NANO” image and in the intensity profile, that the superlens provides significantly higher resolution than the diffraction-limited case.
Nanoscale Optics
Published in Vladimir I. Gavrilenko, Optics of Nanomaterials, 2019
Experimental results and numerical simulations obtained by (Parazzoli et al., 2003) are shown in Fig. 3.14. The deviation of a microwave beam freely propagating in air in NIM and Teflon wedge agreed with the theory very well thus experimentally verifying the concept of the negative index materials. Metamaterials with negative refraction may lead to the development of a superlens capable of imaging objects and fine structures that are much smaller than the wavelength of light (Pendry et al., 2006).
Nanoscale Etching and Deposition
Published in R. Mohan Sankaran, Plasma Processing of Nanomaterials, 2017
Nathan Marchack, Jane P. Chang
There are other top-down techniques discussed in the literature to extend lithographic patterning beyond the diffraction limit. Among these are nanoimprint lithography (NIL),101 quantum interferometric optical lithography (QIOL),102 surface plasmon resonant interference nanolithography (SPRINT),103 and metamaterial-based “superlenses.”104 The NIL method utilizes mechanical molding of polymer materials to create features, which theoretically could overcome the diffraction limit; however, plasma etching is still deeply involved in the process—from the creation of the template molds to the removal of residual polymer on the substrate. However, this approach offers the possibility of hybridization; by implanting metal pads into the template mold it can be used as both a conventional lithographic mask as well as an NIL tool. QIOL is based on the concept of nonclassical entangled photon-number states and theoretically allows for the patterning of features with a minimum CD smaller than the diffraction limit by a factor of N, where N in this case is the number of photons entangled at a time, and also the number absorbed by the substrate. Entangled photon pairs can be generated by spontaneous parametric down-conversion and allow for lithography below the typical limits of diffraction.102 SPRINT relies on the principle that illumination light can be guided with a prism to couple with surface plasmons to obtain a new state with a much shorter wavelength and higher field intensity than that of the illumination light. The resulting enhanced optical field close to the metal mask can then cause localized exposure of a thin resist layer below the mask.103 The superlens concept hinges heavily on “negative index media” (NIM) (i.e., materials with a negative index of refraction). Engineering NIM allows for the enhancement of evanescent waves, which carry fine details about the object but are confined to the near field and subsequently become lost by conventional glass lenses. When utilized in conjunction with a coupling element, the enhanced evanescent waves can be coupled into propagating waves, which makes far-field detection possible. A variation of this idea is the hyperlens, which uses an artificial metamaterial to transfer deep subwavelength information into the far field by a two-stage process. First, evanescent waves are enhanced through surface resonance, followed by conversion into a propagation wave at the exit surface by means of a designed surface scatter.104 Such novel techniques provide examples of expanding the possibilities of plasma etching.
A plasmonic lens based on coordinate transformation
Published in Journal of Modern Optics, 2020
Qiongchan Gu, Yafei Li, Chunhai Hu, Jiangtao Lv, Yu Ying, Xiaoxiao Jiang, Guangyuan Si
Here, we propose an electromagnetic device based on coordinate transformation principles: a metamaterial superlens. Undoubtedly, transformation optics has provided a new method to design optical devices with elegant features. Extensive useful optical devices have been elaborately designed by considering the coordinate transformation principles via different approaches. In addition, more practical applications have been experimentally demonstrated for various specific applications. Such devices possess many unique optical properties and they are crucial for developing applications in beam-steering, spatial light modulating, nanoscale-resolution imaging and biochemical sensing. Moreover, these devices are highly geometric dependent since surface plasmon resonance is mainly determined by structural parameters. Therefore, dynamic control of an optical device with a predesigned function can be readily achieved. Many novel functional devices have been demonstrated using transformation optics and they are intractable or even unrealizable using conventional optical design methods. We propose a device which can modulate electromagnetic waves in a different way compared with traditional lenses. The following part will introduce the designing method and working principles of the device in detail. Then, calculation results are discussed and further compared with the function of traditional lenses, proving that transformation optics can provide a more convenient way to regulate the propagation of electromagnetic waves.