Reconfigurable Flat Optics with Programmable Reflection Amplitude Using Lithography‐Free Phase‐Change Material Ultra‐Thin Films

Cueff, Sébastien; Taute, Arnaud; Bourgade, Antoine; Lumeau, Julien; Monfray, S.; Song, Qinghua; Genevet, Patrice; Devif, Brice; Letartre, Xavier; Berguiga, Lotfi

doi:10.1002/adom.202001291

Cited by 30 publications

(21 citation statements)

References 50 publications

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“…The possibility of being able to control the resonance peak with a crystallization fraction in PCMs is possible because these materials have unique chemical bonding properties, sometimes referred to as resonant or metavalent bonding. [ 17,26 ] Because of the strong electronic polarizabilities of the material in the crystalline state that produce a high value of very large refractive index over a wide wavelength range, n ≈6–7 (Figure 2a) in the region of the infrared electromagnetic spectrum. [ 27 ] The metavalent bond requires a long‐range order between the atoms and is therefore lost when the PCM is in an amorphous state.…”

Section: Resultsmentioning

confidence: 99%

Design of Planar Reconfigurable, Tunable, and Wide Angle Resonant Absorbers for Applications in the IR Spectrum

Souza

Rodríguez-Esquerre

Oliveira

2021

Advcd Theory and Sims

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A hybrid resonant absorber Fabry Perot—FP tunable from a simple stack of planar layers of ultra‐thin films of phase change material is proposed, designed, and demonstrated numerically. This work shows that properly designed metal–dielectric–metal) structures comprising thin films of titanium (Ti), germanium telluride (GeTe) on a silver (Ag) substrate produce a dynamic modulation of light in the near IR with almost perfect absorption (A > 93%). It is demonstrated that the resonant peaks of the hybrid absorber can be tuned in two different ways for any wavelength, with the crystallization fractions and the thickness of the dielectric. The influence of the metallic top layer thickness is also analyzed and demonstrated the fabrication error tolerance of the proposed absorber is demonstrated. Also analyzed is the influence of the thickness of the metallic top layer and tolerance to fabrication error of the proposed absorber is demonstrated. Finally, the physical mechanisms for the coupling of the electromagnetic field and the absorbed optical power in the structure proposed are presented and discussed. This study allows the beginning of the development of hybrid devices to control the absorption of light in the region of the electromagnetic spectrum used in optical communications.

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Section: Resultsmentioning

confidence: 99%

Design of Planar Reconfigurable, Tunable, and Wide Angle Resonant Absorbers for Applications in the IR Spectrum

Souza

Rodríguez-Esquerre

Oliveira

2021

Advcd Theory and Sims

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“…Introduction of loss in the film modifies the phases as shown by solid lines in Figure 4a. The plot demonstrates that in the ITER regime, the reflection phase at the top interface plays a dominant role in determining resonant interferences, which require ϕ 12 ¼ ϕ d , in contrast to those in Fabry-Perot resonances (which is determined by propagation phase in the film) and the previously investigated ultrathin film interferences [11][12][13][14][15][16][17][18][19][20] dominated by reflection phase at the bottom interface. Figure 4b plots the variation in magnitudes of r 12 and e 2iδ for real and lossless ENZ.…”

Section: Spectral and Angular Characteristics Of Infrared Absorptionmentioning

confidence: 89%

“…Such homogeneous ultrathin films are attractive for applications in coloring, filtering, absorption enhancement in photovoltaic applications, infrared absorbers and emitters, and in reconfigurable flat optics. [11][12][13][14][15][16][17][18][19][20] Epsilon-near-zero (ENZ) materials are one such class of thin film materials that have gained much interest in recent times. [21,22] The real part of permittivity (ε 0 ) of ENZ materials becomes zero at the zero-epsilon wavelength (λ ZE ), such that ε 0 is positive (negative) at shorter (longer) wavelengths.…”

Section: Introductionmentioning

confidence: 99%

Tailoring Infrared Absorption and Thermal Emission with Ultrathin Film Interferences in Epsilon‐Near‐Zero Media

Johns

Chattopadhyay

Mitra

2021

Advanced Photonics Research

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Engineering modal dispersions of ultrathin, planar structures enables significant control over infrared perfect absorption (PA) and thermal emission characteristics. Herein, the optical response of ultrathin, low loss, epsilon‐near‐zero (ENZ) films on reflecting surfaces is simulated to investigate the wavelength and angular ranges over which they absorb and emit radiation most efficiently and identify the design parameters that tailor the ENZ mode dispersion of the system. A generic interference model is shown to elucidate the underlying physics of these ultrathin film absorption resonances, occurring well below the conventional quarter‐wavelength thickness limit. While the absorption is spectrally limited to wavelengths where the ENZ film is optically a dielectric with refractive index below unity, the angular spread is delimited by the material dispersion. Further, these resonant interferences are understood to arise from universal wave phenomena, realizable in simple planar structures having appropriate refractive index contrast, not restricted to ENZ materials. The results show that appropriate choice of material, film thickness and loss allows tailoring the modal dispersions, which enables precise directional control and wide tunability in spectral range (width ≈0.1–1.0 μm) of PA and thermal emission, paving the way towards efficient ENZ‐based infrared optical and thermal coatings.

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“…So far, only the cases of fully amorphous and fully crystalline PCM films were considered. It is however well-known that intermediate crystallization states can be accessed by short-time annealing [72][73][74] or optical switching. [48,51,75,76] Thus, the whole absorptance tuning ranges marked in Figure 3b should be accessible with these intermediate states.…”

Section: Continuous Absorption Tuningmentioning

confidence: 99%

Ultra‐Thin Switchable Absorbers Based on Lossy Phase‐Change Materials

Heßler

Bente

Wuttig

et al. 2021

Advanced Optical Materials

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a wavelength causes destructive interference of light and the light is absorbed at the metal surface.Along with current trends to eversmaller, more versatile devices, thin and reconfigurable infrared absorbers which do not require cumbersome nanofabrication are desirable, for example, to fabricate ultra-thin, effective light detectors. This is especially true for the mid-infrared spectral range, where optical imaging devices are important for many technological applications in key areas like thermography, surveillance, automotive safety, and astronomy. [8] It has been shown that ultra-thin absorbers can consist of just an imperfect conductor as a reflector and a very thin, lossy dielectric as the absorbing film because of non-trivial phase shifts at the interfaces. [13] Originally, the absorber functionalities are fixed after fabrication, limiting their application range. To achieve more versatile absorbers, research has been directed towards realizing tunable absorption functionality. [8,[14][15][16][17][18][19][20][21][22] Phase-change materials (PCMs) are especially interesting for this because they offer non-volatile tuning (in contrast to the volatile tuning with transparent conducting oxides or phasetransition materials) by switching between their amorphous and crystalline structural phases whose optical properties differ significantly, because of a unique bonding mechanism, referred to as metavalent bonding. [23][24][25][26] They can be switched between their phases by thermal, [27] electrical, [28] or optical heating [29] on time-scales down to a few nanoseconds [30] and they have already been successfully commercialized in products like re-writable DVDs [29] and PC-RAM. [31] Crystallization leads to an approximately twofold increase of the refractive index in the infrared spectral range for many PCMs [32,33] like Ge 2 Sb 2 Te 5 and its stoichiometric neighbors Ge 3 Sb 2 Te 6 and Ge 8 Sb 2 Te 11 . In addition, these PCMs feature low losses in the infrared, which makes them suitable for many nanophotonics applications [34][35][36] like waveguides, [37,38] photonic memory, [39,40] polaritonics, [41][42][43][44] tunable metasurfaces, [45][46][47][48][49][50][51][52][53] and tunable metasurface absorbers. [8,14,18,[54][55][56][57] But the same low-loss optical properties become disadvantageous for constructing ultra-thin absorbers with thicknesses well beyond the quarterwavelength limit. While their use is still viable in the visible and near-infrared spectral range [58][59][60] where they have significant optical losses, they are no longer suitable at infrared frequencies. Absorbersfor infrared light are important optical components in key areas like biosensing, infrared imaging, and (thermal) light emission, with special need for thin and reconfigurable devices. Here, the authors demonstrate ultra-thin, switchable infrared absorbers based on thin layers of chalcogenide phase-change materials (PCMs) with high optical contrast between a lossless amorphous and an exceptionally lossy crystalline phase (Ge 3 Sb ...

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Reconfigurable Flat Optics with Programmable Reflection Amplitude Using Lithography‐Free Phase‐Change Material Ultra‐Thin Films

Cited by 30 publications

References 50 publications

Design of Planar Reconfigurable, Tunable, and Wide Angle Resonant Absorbers for Applications in the IR Spectrum

Design of Planar Reconfigurable, Tunable, and Wide Angle Resonant Absorbers for Applications in the IR Spectrum

Tailoring Infrared Absorption and Thermal Emission with Ultrathin Film Interferences in Epsilon‐Near‐Zero Media

Ultra‐Thin Switchable Absorbers Based on Lossy Phase‐Change Materials

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