Materials Engineering Newsline … items of interest to JME readers

AbstractActively tunable and reconfigurable wavefront shaping by optical metasurfaces poses a significant technical challenge often requiring unconventional materials engineering and nanofabrication. Most wavefront-shaping metasurfaces can be considered “local” in that their operation depends on the responses of individual meta-units. In contrast, “nonlocal” metasurfaces function based on the modes supported by many adjacent meta-units, resulting in sharp spectral features but typically no spatial control of the outgoing wavefront. Recently, nonlocal metasurfaces based on quasi-bound states in the continuum have been shown to produce designer wavefronts only across the narrow bandwidth of the supported Fano resonance. Here, we leverage the enhanced light-matter interactions associated with sharp Fano resonances to explore the active modulation of optical spectra and wavefronts by refractive-index tuning and mechanical stretching. We experimentally demonstrate proof-of-principle thermo-optically tuned nonlocal metasurfaces made of silicon and numerically demonstrate nonlocal metasurfaces that thermo-optically switch between distinct wavefront shapes. This meta-optics platform for thermally reconfigurable wavefront shaping requires neither unusual materials and fabrication nor active control of individual meta-units.

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Integrated Computational Materials Engineering to Predict Dimensions for Steady-State and Transient Melt-Pool Formation in the Selective Laser Melting of Inconel 625

Integrating Materials and Manufacturing Innovation ◽

10.1007/s40192-021-00223-6 ◽

2021 ◽

Author(s):

Stephen Wormald ◽

Jordan Clingenpeel ◽

Tim Vincent ◽

Anil Chaudhary

Keyword(s):

Steady State ◽

Selective Laser Melting ◽

Inconel 625 ◽

Laser Melting ◽

Materials Engineering ◽

Melt Pool ◽

Integrated Computational Materials Engineering ◽

Computational Materials ◽

Pool Formation

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Recent advancements and perspectives on light management and high performance in perovskite light-emitting diodes

Nanophotonics ◽

10.1515/nanoph-2021-0033 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Shaoni Kar ◽

Nur Fadilah Jamaludin ◽

Natalia Yantara ◽

Subodh G. Mhaisalkar ◽

Wei Lin Leong

Keyword(s):

High Performance ◽

Light Propagation ◽

Light Emission ◽

Review Article ◽

Rapid Progress ◽

Light Emitting ◽

Materials Engineering ◽

Perovskite Materials ◽

Light Management ◽

Photon Recycling

Abstract Perovskite semiconductors have experienced meteoric rise in a variety of optoelectronic applications. With a strong foothold on photovoltaics, much focus now lies on their light emission applications. Rapid progress in materials engineering have led to the demonstration of external quantum efficiencies that surpass the previously established theoretical limits. However, there remains much scope to further optimize the light propagation inside the device stack through careful tailoring of the optical processes that take place at the bulk and interface levels. Photon recycling in the emitter material followed by efficient outcoupling can result in boosting external efficiencies up to 100%. In addition, the poor ambient and operational stability of these materials and devices restrict further commercialization efforts. With best operational lifetimes of only a few hours reported, there is a long way to go before perovskite LEDs can be perceived as reliable alternatives to more established technologies like organic or quantum dot-based LED devices. This review article starts with the discussions of the mechanism of luminescence in these perovskite materials and factors impacting it. It then looks at the possible routes to achieve efficient outcoupling through nanostructuring of the emitter and the substrate. Next, we analyse the instability issues of perovskite-based LEDs from a photophysical standpoint, taking into consideration the underlying phenomena pertaining to defects, and summarize recent advances in mitigating the same. Finally, we provide an outlook on the possible routes forward for the field and propose new avenues to maximally exploit the excellent light-emitting capabilities of this family of semiconductors.

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