Wide Bandgap Phase Change Material Tuned Visible Photonics

Dong, Weiling; Liu, Hailong; Behera, Jitendra K.; Lu, Li; Ng, Ray Jia Hong; Sreekanth, Kandammathe Valiyaveedu; Zhou, Xilin; Yang, Joel K. W.; Simpson, Robert E.

doi:10.1002/adfm.201806181

Cited by 248 publications

(226 citation statements)

References 42 publications

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“…The layer thickness is typically ∼10 nm and the large number of interfaces means that inter-diffusion over nanometer distances can be a real problem. Thus, it is important to identify plasmonic materials that can directly interface with Ge 2 Sb 2 Te 5 , and other important phase change chalcogenides [26], without inter-diffusion between the metal and the PCM layers occuring.…”

Section: Introductionmentioning

confidence: 99%

Inter-diffusion of plasmonic metals and phase change materials

Dong

Behera

et al. 2018

J Mater Sci

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This work investigates the diffusion of metal atoms into phase change chalcogenides, which is problematic because it can destroy resonances in photonic devices. Interfaces between Ge 2 Sb 2 Te 5 and metal layers were studied using X-ray reflectivity (XRR) and reflectometry of metal-Ge 2 Sb 2 Te 5 layered stacks. The diffusion of metal atoms influences the crystallisation temperature and optical properties of phase change materials. When Au, Ag, Al, W structures are directly deposited on Ge 2 Sb 2 Te 5 , inter-diffusion occurs. Indeed, Au reacts with Ge 2 Sb 2 Te 5 to form a AuTe 2 layer at the interface. Diffusion barrier layers, such as Si 3 N 4 or stable plasmonic materials, such as TiN, can prevent the interfacial damage. This work shows that the interfacial diffusion must be considered when designing phase change material tuned photonic devices, and that TiN is the most suitable plasmonic material to interface directly with Ge 2 Sb 2 Te 5 .

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Section: Introductionmentioning

confidence: 99%

Inter-diffusion of plasmonic metals and phase change materials

Dong

Behera

et al. 2018

J Mater Sci

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“…Unlink the PCM GST, Sb 2 S 3 has a bandgap of 2 eV, which renders it transmissive in the visible spectrum. Moreover, the dielectric function of Sb 2 S 3 exhibits a substantial change in the visible frequencies when the structure of the material is switched from amorphous to crystalline phase . To avoid diffusion problems typical of noble metals, TiN has been selected as a plasmonic component in the designed HMM.…”

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confidence: 99%

Phase‐Change‐Material‐Based Low‐Loss Visible‐Frequency Hyperbolic Metamaterials for Ultrasensitive Label‐Free Biosensing

Sreekanth

Ouyang

Sreejith

et al. 2019

Advanced Optical Materials

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The extreme anisotropic permittivity of hyperbolic metamaterials (HMMs) represent a unique opportunity to realize effective bulk metastructures with extraordinary optical properties over a broad frequency range from visible to terahertz. [1] HMMs are artificial uniaxial materials that exhibit hyperbolic dispersion because the out of plane dielectric constant (ε zz = ε ⊥ ) has an opposite sign to the in-plane dielectric constants (ε xx = ε yy = ε ll ). HMMs can be classified into two types based on the sign of their dielectric components, i.e., type I (−ε ⊥ and ε ll ) and type II (ε ⊥ and −ε ll ). In comparison to isotropic materials showing elliptical dispersion, HMMs support propagation of optical modes across the structure with infinitely large momentum (high-k modes) in the effective medium limit, [2,3] irrespective of Hyperbolic metamaterials (HMMs) have emerged as a burgeoning field of research over the past few years as their dispersion can be easily engineered in different spectral regions using various material combinations. Even though HMMs have comparatively low optical loss due to a single resonance, the noble-metal-based HMMs are limited by their strong energy dissipation in metallic layers at visible frequencies. Here, the fabrication of noble-metal-free reconfigurable HMMs for visible photonic applications is experimentally demonstrated. The low-loss and active HMMs are realized by combining titanium nitride (TiN) and stibnite (Sb 2 S 3 ) as the phase change material. A reconfigurable plasmonic biosensor platform based on active Sb 2 S 3 -TiN HMMs is proposed, and it is shown that significant improvement in sensitivity is possible for small molecule detection at low concentrations. In addition, a plasmonic apta-biosensor based on a hybrid platform of graphene and Sb 2 S 3 -TiN HMM is developed and the detection and real-time binding of thrombin concentration as low as 1 × 10 −15 m are demonstrated. A biosensor operating in the visible range has several advantages including the availability of sources and detectors in this region, and ease of operation particularly for point-of-care applications.

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“…Exploiting epsilon‐near‐zero transitions such as the one for GST could open another path for realizing adaptive phase‐change metasurfaces in the visible spectral range . Besides this, identifying new phase‐change materials with improved characteristics in the visible spectral range is another topic of ongoing research and may enable more advanced adaptive metasurfaces in this spectral range in the future . A practical limitation of PCMs is the requirement of dedicated, costly fabrication tools and experience in the deposition process for achieving high material quality.…”

Section: Adaptive Metasurfacesmentioning

confidence: 99%

Optical Metasurfaces: Evolving from Passive to Adaptive

Hail

Michel

Poulikakos

et al. 2019

Advanced Optical Materials

121

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of ultrathin, artificial surfaces, so-called metasurfaces, for manipulating the propagation of light at will. [1,2] Metasurfaces control the propagation of light by abruptly changing its phase, amplitude, polarization, or spectrum at a surface and within a thin (quasi-2D) layer using large arrays of optical scatterers with subwavelength separation. Ideally, each scatterer can be independently engineered in order to locally influence the wavelets of the impinging light, and therefore, arbitrarily reform the wavefront. This concept has been exploited to create a variety of flat optical elements such as beam deflectors, [3][4][5] lenses, [6][7][8] and holograms. [9,10] As compared to bulky refraction-based optical elements, these surfaces are of subwavelength or wavelength-scale thickness, which enables their integration into compact devices. A main feature of the majority of such flat optical elements is that they are passive, and once fabricated, their optical functionalities are invariable. A beam deflector of this kind will direct light of a certain wavelength and direction always into the same direction, or a lens will focus light always to the same focal point. A broad range of new applications could be enabled if it were possible to actively and reversibly change the functionality of metasurfaces after their fabrication. With such "adaptive" metasurfaces beam deflectors with adjustable angle of deflection, metalenses with variable focal length or dynamic holograms may be realized. Advances toward such active devices are highly relevant for applications such as light detection and ranging [11] (LIDAR) sensing for driverless cars, dynamic zoom lenses for miniaturized camera systems [12] (e.g., in smartphones), or holographic displays for augmented reality devices. [13] An adaptive metasurface allows for the dynamic adjustment of an optical functionality of the surface. As shown in Figure 1, for the specific case of a metalens, these surfaces can be categorized based on their degree of dynamic adaptivity. While a passive surface has a fixed functionality, a switchable metasurface allows for switching back and forth between two (or more) predefined states (e.g., switching between different focal lengths, deflection angles, or hologram images). A continuously tunable metasurface enables continuous adjustment of a property within a range (e.g., tunable focal length or deflection angle). Finally, a freely tunable metasurface allows for continuous, arbitrary adjustment of a property, for example, 3D adjustment of the focal point of the metalens shown in Figure 1. Adaptive functionalities can be added to metasurfaces with different methods, for example, by mechanically rearranging the scatterers on the surface with respect to each other, or modifying

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Wide Bandgap Phase Change Material Tuned Visible Photonics

Cited by 248 publications

References 42 publications

Inter-diffusion of plasmonic metals and phase change materials

Inter-diffusion of plasmonic metals and phase change materials

Phase‐Change‐Material‐Based Low‐Loss Visible‐Frequency Hyperbolic Metamaterials for Ultrasensitive Label‐Free Biosensing

Optical Metasurfaces: Evolving from Passive to Adaptive

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