Edge‐Orientation Dependent Nanoimaging of Mid‐Infrared Waveguide Modes in High‐Index PtSe<sub>2</sub>

Wong, Kin Ping; Hu, Xin; Lo, Tsz Wing; Guo, Xuyun; Fung, Kin Hung; Zhu, Ye; Lau, Shu Ping

doi:10.1002/adom.202100294

Cited by 10 publications

(9 citation statements)

References 55 publications

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“…In combination with cryogenic near-field microscopy, exciton polaritons that are anisotropic and self-hybridized or highly confined could thus be imaged. Finally, our technique is also easily transferrable to the visible or mid-infrared range, paving the way for a full characterization of novel materials for nanophotonic applications across various spectral ranges.…”

Section: Discussionmentioning

confidence: 99%

In-Plane Anisotropy in Biaxial ReS₂ Crystals Probed by Nano-Optical Imaging of Waveguide Modes

et al. 2022

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Near-field imaging has emerged as a reliable probe of the dielectric function of van der Waals crystals. In principle, analyzing the propagation patterns of subwavelength waveguide modes (WMs) allows for the extraction of the full dielectric tensor. Yet, previous studies have mostly been restricted to high-symmetry materials or narrowband probing. Here, we resolve in-plane anisotropic WMs in thin rhenium disulfide (ReS 2 ) crystals across a wide range of near-infrared frequencies. By tracing the evolution of these modes as a function of crystallographic direction, polarization of the electric field, and sample thickness, we have determined the anisotropic dielectric tensor, including the elusive out-of-plane response. The excitonic absorption at ∼1.5 eV manifests itself as a clear backbending feature in the WM dispersion and a reduction of the quality factors as fully supported by numerical calculations. Our results extend the sensitivity of near-field microscopy toward biaxial anisotropy and provide key insights into the optoelectronic properties of ReS 2 .

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Section: Discussionmentioning

confidence: 99%

In-Plane Anisotropy in Biaxial ReS₂ Crystals Probed by Nano-Optical Imaging of Waveguide Modes

et al. 2022

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“…Instead, the tip-launched waveguide modes interfere with the tip scattered light and form interference fringe patterns depending on the incident angle. The relationship between different rotation angles, the interference fringe wavevectors q obs , and the in-plane wavevectors q wm can be expressed as 52 where . Thereby, the wavevector q wm can be extracted from the complicated interference patterns.…”

Section: Resultsmentioning

confidence: 99%

Visible to mid-infrared giant in-plane optical anisotropy in ternary van der Waals crystals

Feng,

Chen,

et al. 2023

Nat Commun

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Birefringence is at the heart of photonic applications. Layered van der Waals materials inherently support considerable out-of-plane birefringence. However, funnelling light into their small nanoscale area parallel to its out-of-plane optical axis remains challenging. Thus far, the lack of large in-plane birefringence has been a major roadblock hindering their applications. Here, we introduce the presence of broadband, low-loss, giant birefringence in a biaxial van der Waals materials Ta2NiS5, spanning an ultrawide-band from visible to mid-infrared wavelengths of 0.3–16 μm. The in-plane birefringence Δn ≈ 2 and 0.5 in the visible and mid-infrared ranges is one of the highest among van der Waals materials known to date. Meanwhile, the real-space propagating waveguide modes in Ta2NiS5 show strong in-plane anisotropy with a long propagation length (>20 μm) in the mid-infrared range. Our work may promote next-generation broadband and ultracompact integrated photonics based on van der Waals materials.

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“…This is analogous to ordinary and extraordinary rays in bulk anisotropic crystals, it has been proven in reference [17]. The thickness dispersion of TE and TM modes in this system can be obtained by the following equations maximum value of GaP nanowire Δn is 0.8) [7][8][9][10] and some results of measurements of the same type of work (Δn of hBN at 633 nm is 0.58, Δn of MoS 2 at 1530 nm is 1.4, and Δn of PtSe 2 at mid-infrared is 0.56) [17,48], the giant optical birefringence indicates that WS 2 is a promising candidate for integrated phase retardation application.…”

mentioning

confidence: 80%

Giant optical anisotropy of WS₂ flakes in the visible region characterized by Au substrate assisted near-field optical microscopy

Deng¹,

Long²,

Wang³

et al. 2022

Nanotechnology

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Transition metal dichalcogenides (TMD) have attracted considerable attention in the field of photonic integrated circuits due to their giant optical anisotropy. However, on account of their inherent loss in the visible region and the difficulty of measuring high refractive index materials, near-field characterizations of the optical anisotropy of TMD in the visible region have inherent experimental difficulties. In this work, we present a systematical characterization of the optical anisotropy in tungsten disulfide (WS2) flakes by using scattering-type scanning near-field optical microscopy (s-SNOM) excited at 671 nm. Transverse-electric (TE) and transverse-magnetic (TM) waveguide modes can be excited in WS2 flakes with suitable thickness, respectively. With the assistance of the Au substrate, the contrast of the near-field fringes is enhanced in comparison with the SiO2 substrate. By combining waveguide mode near-field imaging and theoretical calculations, the in-plane and out-of-plane refractive indexes of WS2 are determined to be 4.96 and 3.01, respectively, indicating a high birefringence value up to 1.95. This work offers experimental evidence for the potential application of WS2 in optoelectronic integrated circuits in the visible region.

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Edge‐Orientation Dependent Nanoimaging of Mid‐Infrared Waveguide Modes in High‐Index PtSe₂

Cited by 10 publications

References 55 publications

In-Plane Anisotropy in Biaxial ReS₂ Crystals Probed by Nano-Optical Imaging of Waveguide Modes

In-Plane Anisotropy in Biaxial ReS₂ Crystals Probed by Nano-Optical Imaging of Waveguide Modes

Visible to mid-infrared giant in-plane optical anisotropy in ternary van der Waals crystals

Giant optical anisotropy of WS₂ flakes in the visible region characterized by Au substrate assisted near-field optical microscopy

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Edge‐Orientation Dependent Nanoimaging of Mid‐Infrared Waveguide Modes in High‐Index PtSe2

Cited by 10 publications

References 55 publications

In-Plane Anisotropy in Biaxial ReS2 Crystals Probed by Nano-Optical Imaging of Waveguide Modes

In-Plane Anisotropy in Biaxial ReS2 Crystals Probed by Nano-Optical Imaging of Waveguide Modes

Visible to mid-infrared giant in-plane optical anisotropy in ternary van der Waals crystals

Giant optical anisotropy of WS2 flakes in the visible region characterized by Au substrate assisted near-field optical microscopy

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Edge‐Orientation Dependent Nanoimaging of Mid‐Infrared Waveguide Modes in High‐Index PtSe₂

In-Plane Anisotropy in Biaxial ReS₂ Crystals Probed by Nano-Optical Imaging of Waveguide Modes

In-Plane Anisotropy in Biaxial ReS₂ Crystals Probed by Nano-Optical Imaging of Waveguide Modes

Giant optical anisotropy of WS₂ flakes in the visible region characterized by Au substrate assisted near-field optical microscopy