Loss compensation in metamaterials and plasmonics with virtual gain [Invited]

Abstract

Metamaterials and plasmonics potentially offer an ultimate control of light to enable a rich number of non-conventional devices and a testbed for many novel physical phenomena. However, optical loss in metamaterials and plasmonics is a fundamental challenge rendering many conceived applications not viable in practical settings. Many approaches have been proposed so far to mitigate losses, including geometric tailoring, active gain media, nonlinear effects, metasurfaces, dielectrics, and 2D materials. Here, we review recent efforts on the less explored and unique territory of “virtual gain” as an alternative approach to combat optical losses. We define the virtual gain as the result of any extrinsic amplification mechanism in a medium. Our aim is to accentuate virtual gain not only as a promising candidate to address the material challenge, but also as a design concept with broader impacts.

Coherent amplification and inversion less lasing of surface plasmon polaritons in a negative index metamaterial with a resonant atomic medium

“…Here, we assume Pr 3+ impurities within a transparent crystal that acts as a one-dimensional chain, and hence our methodology to exciting directional SSPP is valid due to experimental feasibility. Next, our amplification scheme is also based on ultra-low loss propagation of the weak SPP field, which is a valid concept and the experimental/theoretical feasibility has been extensively discussed recently 67 . Finally, we elucidate field amplification through parametric resonance, which is a valid methodology for inducing amplification in dynamical systems such as micro-electro-mechanical systems 86 and superconducting cavities 87 .…”

“…To suppress this unwanted loss we suggest virtual gain technique, which is extensively discussed in Ref. 67 . This coherent amplification without need to population and high-input power of SPP fields thus open prospects for applications in wide research areas from biology and sensing to interconnects 18 .…”

“…To this aim, various mechanism such as optical parametric amplification 62 , geometrical tailoring and optimization 63 , including gain media 64 and meta-surfaces 65 serve to combat the Ohmic loss related to plasmonic structures, specifically for optical frequencies. However, we introduce a virtual gain to our hybrid interface by employing a coherent method, which is based on constructive interference of the two externally injected plasmonic fields and also excited signal SPP field to suppress the Ohmic loss of this NIMM layer 66,67 . This loss-compensation is basically different from the stimulated optical loss suppression achieved by dye molecules or amplification induced in integrated plasmonic chip 64,68 .…”

Non-Hermitian Electromagnetic Metasurfaces at Exceptional Points (Invited Review)

“…where γ ave = (γ 1 + γ 2 )/2 is the average loss of the two components, and γ diff = (γ 1 − γ 2 )/2 is the contrast of the two losses. Thus, a "virtual gain" can be achieved to combat the loss [32]. We can still define exact-PT phase and broken-PT phase by H P T , although H is offset by a global loss H L with eigenvalues that are no longer real [26].…”

Experimental realization of the active convolved illumination imaging technique for enhanced signal-to-noise ratio

“…Subwavelength optical engineering through metamaterials and metasurfaces offer unprecedented opportunities in a wide range of applications such as superresolution imaging [5][6][7][8][9][10][11], photolithography [12,13], wireless and optical communications [14,15], multifunctional and flat optics and photonics [16][17][18][19][20], metalenses [21], intelligent metaphotonics [22], light detection and ranging [23], autonomous vehicles [24], and quantum information [25][26][27]. However, the photon losses hinder their further viability [28][29][30]. Inspiration from research in loss compensation for metamaterials and plasmonics employing 'virtual gain' [30][31][32][33] led us to propose a unique perspective on the noisy imaging problem [2,32,[34][35][36][37][38][39][40][41].…”