Plasmon Injection to Compensate and Control Losses in Negative Index Metamaterials

Abstract

Metamaterials have introduced a whole new world of unusual materials with functionalities that cannot be attained in naturally occurring material systems by mimicking and controlling the natural phenomena at subwavelength scales. However, the inherent absorption losses pose fundamental challenge to the most fascinating applications of metamaterials. Based on a novel plasmon injection (PI or )-scheme, we propose a coherent optical amplification technique to compensate losses in metamaterials. Although the proof of concept device here operates under normal incidence only, our proposed scheme can be generalized to arbitrary form of incident waves. The -scheme is fundamentally different than major optical amplification schemes. It does not require gain medium, interaction with phonons, or any nonlinear medium. The -scheme allows for loss-free metamaterials. It is ideally suited for mitigating losses in metamaterials operating in the visible spectrum and is scalable to other optical frequencies. These findings open the possibility of reviving the early dreams of making "magical" metamaterials from scratch. PACS numbers:Metamaterials have led to previously unthought-of applications such as flat lens [1], perfect lens [2], hyperlens [3][4][5], ultimate illusion optics [6][7][8], perfect absorber [9,10], optical analog simulators [11,12], metaspacers [13], and many others. Despite tremendous progress in theory and experimental realizations, the major current challenges seem to further delay the metamaterial era to come. For instance, achieving full isotropy, feasible fabrication methods, broad bandwidth, and compensation of dissipative losses especially at optical frequencies are among the challenges yet to be solved [14,15]. Perhaps, the most critical of all is how to avoid optical losses -especially in large-volume structures. The performance of devices utilizing metamaterials dramatically degrades at optical frequencies due to significant ohmic losses arising from the metallic constituents. The strategies proposed to mitigate the losses include passive reduction and active compensation schemes. Avoiding sharp edges [16], reducing skin depths [16][17][18], and classical analog of electromagnetically induced transparency are proposed as passive loss minimization techniques [19,20]. Constitutive materials such as dielectrics [21], nitrides [22], oxides [23], graphene [24], and superconductors [24-30] have also been explored for possible alternatives to lossy conductors. However, none of these materials have so far shown to outperform the performance of high-conductivity metals at room temperature [31,32]. Active compensation of losses using gain medium has been emerged as the most promising strategy to avoid the deleterious impacts of losses on metamaterial devices. Optically pumped semiconductor quantum dots and quantum wells incorporated in planar metamaterials have been experimentally shown to compensate the losses to some extent [33][34][35][36][37][38]. A remarkable improvement in the figure of merit (FOM) of a ...

Review of near-field optics and superlenses for sub-diffraction-limited nano-imaging

“…63 In contrast to many other loss compensation methods, the Π scheme requires no gain medium, thus eliminates its associated complexities. Instead, full compensation is achieved not by traditional amplification but by the coherent superposition of externally-driven "auxiliary" modes with the eigenmodes of a NIM.…”

“…Surface plasmon polaritons are injected from auxiliary ports through a metallic grating structure, which are then superimposed with the native eigenmodes in the metamaterial. The Π scheme allows for diverging figure-of-merit (i.e., loss free metamaterial), and has been demonstrated to provide near-perfect loss compensation for superlenses 63,64 and hyperlenses 65 applied to sub-diffraction-limited imaging. For imaging, applying the Π scheme is equivalent to a simple spatial filtering procedure, or superposition of the original source with an auxiliary source as shown in Fig.…”

“…16,48 Fortunately, a number of promising loss compensation methods have appeared, including the employment of gain media, [49][50][51][52][53][54][55][56][57][58][59] geometric tailoring, 60 and plasmon injection. [61][62][63][64][65] Somewhat surprisingly, there is less detailed treatment given in the literature to the practical matter of extracting the image from a near-field superlens than one might expect. Since the image is focused into the near-field, one may wonder why there is any interest in superlensing at all if there is still a need for additional employment of a scanning microscope.…”

Parametric study of modified dipole nano‐antennas printed on thick substrates for infrared energy harvesting

“…In contrast to RF and microwave antennas, whose resonances occur when the size of the structure is on the order of a half‐wavelength in free space, the resonance in nano‐antennas is associated with plasmonic effects in the conducting parts of the antennas, especially at optical frequencies . In fact, the excitation of a nano‐antenna by an incident field induces the oscillations of free electrons in the conductors which in turn create surface plasmon polaritons (SPPs) …”

“…4 In fact, the excitation of a nano-antenna by an incident field induces the oscillations of free electrons in the conductors which in turn create surface plasmon polaritons (SPPs). [6][7][8][9][10] The concept of plasmonic resonance that occurs when an incident electromagnetic wave hits a metal surface inducing a SPPs has explained many physical phenomena giving arise to new applications in optical and IR ranges such as optical biosensors, absorbers, superlens, clocking, and energy harvesting.…”