Manipulating polaritons at the extreme scale in van der Waals materials

Abstract

Polaritons, originating from the interactions between photons and material excitations, have attracted significant attention due tobecause of their strong field compression and deeply subdiffractional scales.Towards For practical implementationapplications, it is crucial to manipulate polaritons efficiently, which but doing so has remainsned challenging because of the relatively poor tunability of traditional polaritonic media. Fortunately, polaritons emerging fromhosted by van der Waals (vdW) materials in the past decade offer unprecedentedallow for new opportunities to tackle this difficulty. Here weWe review the state -of -the -art advancements in the manipulation of polaritons at the extreme scale in vdW materials, arranged by their working mechanisms. Benefiting from the vast large and expanding catalogue of vdW materials and associated architectures and techniques, more accessible manipulation strategies are expected, not only offering the control of light at the nanoscale with novel new degrees of freedom, but also shedding new light onoffering insight into nanophotonics, meta-optics, topological physics, and quantum materials.

Two-dimensional natural hyperbolic materials: from polaritons modulation to applications

“…To exploit more natural HMs and activate their hyperbolicity in a wider spectral range, it is necessary to attempt more approaches (being crucial to the onset frequency of hyperbolicity and the permittivity 93,[151][152][153][154] ) to modify the electric structures and energy bands of anisotropic layered crystals. The potential approaches include but are not limited to controlling the temperature, 37 straining, 10 doping, 53 photoexcitation, 155 and external stimuli to the dielectric environment of HMs, 49 etc.…”

“…In the strong coupling regime, hyperbolic polaritons have great potential for non-destructive molecule sensing and point-of-care medical diagnostics. 49 (7) The uniqueness of 2D natural HMs is their atomic thickness, which is of great significance for highly compact and integrated devices. In future device applications, large-area and high-quality crystallized natural HMs are highly desirable.…”

“…The propagation length is greatly affected by damping pathways which are tightly correlated with the polaritonic materials themselves and the surrounding dielectric environment. 49 It is seen from Table 2 that the L p values for hyperbolic phonon polaritons can change from ∼500 to ∼2000 nm through switching polaritonic materials and tuning the external physical conditions.…”

“…7,15,[24][25][26]46 Although some reviews about natural HMs have been also published, they are restricted to either only reviewing hyperbolic phonon polaritons in materials (e.g., hBN, α-MoO 3 , α-V 2 O 5 , and β-Ga 2 O 3 ) or solely introducing hyperbolic plasmon polaritons in black phosphorus (BP) and WTe 2 . 7,[42][43][44]47 Comparisons and discussions of phonon polaritons, plasmon polaritons, and exciton polaritons have been also made by W. Ma et al and Y. Wu et al 48,49 However, their reviews focus on either in-plane anisotropic polaritons or manipulation strategies for polaritons in vdW materials, from which many recently reported 2D natural HMs (e.g., ZrSiSe, β-Ga 2 O 3 , perovskites and tetradymites) along with the related hyperbolic properties are missing. 48,49 In particular, hyperbolic exciton and shear polaritons have recently been experimentally identified in tetradymites and β-Ga 2 O 3 , respectively.…”

“…7,[42][43][44]47 Comparisons and discussions of phonon polaritons, plasmon polaritons, and exciton polaritons have been also made by W. Ma et al and Y. Wu et al 48,49 However, their reviews focus on either in-plane anisotropic polaritons or manipulation strategies for polaritons in vdW materials, from which many recently reported 2D natural HMs (e.g., ZrSiSe, β-Ga 2 O 3 , perovskites and tetradymites) along with the related hyperbolic properties are missing. 48,49 In particular, hyperbolic exciton and shear polaritons have recently been experimentally identified in tetradymites and β-Ga 2 O 3 , respectively. 50,51 A comprehensive comparison of hyperbolic phonon, plasmon, exciton, and shear polaritons remains lacking.…”