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The Casimir force acts on nearby surfaces due to zero-point fluctuations of the quantum electromagnetic field. In the nonretarded limit, the interaction is also known as the van der Waals force. When the electromagnetic response of the surfaces is anisotropic, a torque may act on the surfaces. Here, we review the literature and recent developments on the Casimir torque. The theory of the Casimir torque is discussed in an explicit example for uniaxial birefringent plates. Recent theoretical predictions for the Casimir torque in various configurations are presented. A particular emphasis is made on experimental setups for measuring the Casimir torque. 

The fixed post-manufacturing properties of metal-based photonic devices impose limitations on their adoption in dynamic photonics. Modulation approaches currently available (e.g. mechanical stressing or electrical biasing) tend to render the process cumbersome or energy-inefficient. Here we demonstrate the promise of utilizing magnesium (Mg) in achieving optical tuning in a simple and controllable manner: etching in water. We revealed an evident etch rate modulation with the control of temperature and structural dimensionality. Further, our numerical calculations demonstrate the substantial tuning range of optical resonances spanning the entire visible frequency range with the etching-induced size reduction of several archetypal plasmonic nanostructures. Our work will help to guide the rational design and fabrication of bio-degradable photonic devices with easily tunable optical responses and minimal power footprint.

 

Abstract Quantum optics combines classical electrodynamics with quantum mechanics to describe how light interacts with material on the nanoscale, and many of the tricks and techniques used in nanophotonics can be extended to this quantum realm. Specifically, quantum vacuum fluctuations of electromagnetic fields experience boundary conditions that can be tailored by the nanoscopic geometry and dielectric properties of the involved materials. These quantum fluctuations give rise to a plethora of phenomena ranging from spontaneous emission to the Casimir effect, which can all be controlled and manipulated by changing the boundary conditions for the fields. Here, we focus on several recent developments in modifying the Casimir effect and related phenomena, including the generation of torques and repulsive forces, creation of photons from vacuum, modified chemistry, and engineered material functionality, as well as future directions and applications for nanotechnology. 

Structural color filters have recently blossomed as a superior alternative to organic dyes or chemical pigments owing to their remarkable durability and compactness. With appropriate design, nanostructure‐induced photonic or plasmonic resonance modes can give rise to either enhancement in transmission or suppression in the reflection within specific wavelength ranges in the optical regime, generating distinctive colors. However, the static optical properties due to fixed structural geometry and size after fabrication hinder their deployment in many cutting‐edge technologies requiring adaptive complexion changes. Here, a multilayer thin film‐based color filter incorporating Mg and MgO, earth‐abundant and biodegradable materials, is devised. The devices display vivid hues spanning a broad gamut via the control of the film thickness. They also exhibit minimal color changes with varying angle views up to 40°–50°. Moreover, the tones fade away instantly upon immersion in water and then progressively transition to a different hue with the complete removal of the Mg‐containing layers, realizing transient color responses. This approach holds great promise for alternative pixels with irreversible color‐change capability as well as zero‐power consumption and low cost, while making use of biodegradable materials.

 

In most process control systems nowadays, process measurements are periodically collected and archived in historians. Analytics applications process the data, and provide results offline or in a time period that is considerably slow in comparison to the performance of many manufacturing processes. Along with the proliferation of Internet-of-Things (IoT) and the introduction of "pervasive sensors" technology in process industries, increasing number of sensors and actuators are installed in process plants for pervasive sensing and control, and the volume of produced process data is growing exponentially. To digest these data and meet the ever-growing requirements to increase production efficiency and improve product quality, there needs a way to both improve the performance of the analytic system and scale the system to closely monitor a much larger set of plant resources. In this paper, we present a real-time data analytics platform, referred to as RT-DAP, to support large-scale continuous data analytics in process industries. RT-DAP is designed to be able to stream, store, process and visualize a large volume of real-time data flows collected from heterogeneous plant resources, and feedback to the control system and operators in a real-time manner. A prototype of the platform is implemented on Microsoft Azure. Our extensive experiments validate the design methodologies of RT-DAP and demonstrate its efficiency in both component and system levels. 

Near‐zero‐index (NZI) materials are becoming increasingly important for photonic designs because they enable new ways to control light–matter interactions at the nanoscale. Many device prototypes that utilize NZI layers are created under conditions that are tool and laboratory specific, making widespread utilization and scalability of NZI materials difficult. Herein, this limitation is circumvented by using transparent conducting oxides (TCOs) produced from scalable commercial sources. The optical response of 49 distinct TCOs with NZI behavior from 12 different suppliers is quantified, including indium tin oxide (ITO), aluminum‐doped zinc oxide (AZO), and fluorine‐doped tin oxide (FTO). The measurements reveal that the ITO samples have the strongest NZI resonances with many samples exhibiting |n| < 0.6 with resonances occurring between 1150 and 1350 nm. Conversely, the FTO and AZO films present higher values of |n| (ranging from 0.6 to 0.9) at 1500–1900 nm. The optical properties, resistivities, and roughness values for all thin films are reported, creating a useful database for device design. Finally, novel NZI phenomena, such as the strong suppression of non‐normal incidence illumination using the data collected from these samples, are demonstrated, opening the door to new opportunities for both research‐grade and mass‐produced NZI devices.