Lifeboat Foundation

Relying on sub-wavelength nanostructures, metasurfaces have been shown as promising candidates for replacing conventional free-space optical components by arbitrarily manipulating the amplitude, phase, and polarization of optical wavefronts in certain applications^1,2,3. In recent years, the scope of their applications has been expanded towards complete spatio-temporal control through the introduction of active metasurfaces. These developments open up exciting new possibilities for dynamic holography⁴, faster spatial light modulators⁵, and fast optical beam steering for LiDAR⁶. Large efforts have been channeled into various modulation mechanisms⁷. Microelectromechanical and nanoelectromechanical systems (MEMS and NEMS)^8,9,10,11 have the advantages of low-cost and CMOS-compatibility, but the speed is limited up to MHz. Phase-change materials^12,13,14 have fast, drastic, and non-volatile refractive index change, but lack continuous refractive index tuning and have a limited number of cycles constraining applicability to reconfigurable devices. Through molecule reorientation, liquid crystal can have index modulation over 10%, while under relatively low applied voltages Tunable liquid crystal metasurfaces, U.S. patent number 10,665,953 [Application Number 16/505,687]¹⁵. Techniques of liquid crystal integration have also advanced after decades of development. However, the tuning speeds are limited to kHz range¹⁶. Thermal-optic effects can induce relatively large refractive index changes^17,18, but the speed is inherently limited and the on-chip thermal management can be challenging. The co-integration of transparent conductive oxide and metallic plasmonic structures^5,6 has been demonstrated in epsilon-near-zero (ENZ) regime to control the wavefront of reflected light, but the low reflection amplitude induced by the optical loss of the materials and the ENZ regime is unavoidable.

In modern photonics, a multitude of technologies for tunable optics and frequency conversion^19,20 are realized with nonlinear materials that have low loss and a strong χ effect, such as lithium niobate^21,22, aluminum nitride²³, and organic electro-optic (OEO) materials²⁴. Their ultrafast responses make it possible to use RF or millimeter-wave control²⁵. Developments in computational chemistry have also led to artificially engineered organic molecules that have record-high nonlinear coefficients with long-term and high-temperature stability^26,27. However, their potential in modifying free-space light has been relatively unexplored until recently. Several OEO material-hybrid designs have demonstrated improved tunability of metasurfaces^28,29,30. Utilizing dielectric resonant structures and RF-compatible coplanar waveguides, a free-space silicon-organic modulator has recently accomplished GHz modulation speed³¹. However, all demonstrations to date require high operating voltages ± 60V, due to low resonance tuning capability (frequency shift / voltage), which hinders their integration with electronic chips.

In this work, we propose combining high-Q metasurfaces based on slot-mode resonances with the unique nano-fabrication techniques enabled by OEO materials, which drastically reduces the operating voltage. The low voltage is mainly achieved from the ability to place the electrodes in close proximity to each other while hosting high-Q modes in between and the large overlap of the optical and RF fields in OEO materials. In the following sections, we first provide the design concepts and considerations for achieving a reduced operating voltage. Next, we numerically demonstrate the advantage of a particular selected mode compared to other supported modes in the structure. Finally, we experimentally realize our concepts and characterize the performance of the electro-optic metasurface.

Read The Article Here https://time.com/6208174/maybe-the-universe-thinks/The concept that the Universe resembles a brain, a neural network, or a self-organizi…

Researchers at Trinity College Dublin, working together with the Royal College of Surgeons in Ireland (RCSI), have developed special fluorescent, color-changing dyes that, for the first time, can be used to simultaneously visualize multiple distinct biological environments using only one singular dye.

When these dyes are encapsulated in delivery vessels, like those used in technologies like the COVID-19 vaccines, they “switch on” and give out light via a process called “aggregation-induced emission” (AIE). Soon after delivery into the cells their light “switches off” before “switching on” again once the cells shuttle the dyes into cellular lipid droplets.

CERN is designing the largest and most powerful supercollider of all time. It could solve some of the biggest mysteries of our universe.

Year 2021 face_with_colon_three

Because they lack an atmosphere, the moon and other airless bodies such as asteroids can build up an electric field through direct exposure to the sun and surrounding plasma. On the moon, this surface charge is strong enough to levitate dust more than 1 meter above the ground, much the way static electricity can cause a person’s hair to stand on end.

Engineers at NASA and elsewhere have recently proposed harnessing this natural surface charge to levitate a glider with wings made of Mylar, a material that naturally holds the same charge as surfaces on airless bodies. They reasoned that the similarly charged surfaces should repel each other, with a force that lofts the glider off the ground. But such a design would likely be limited to small asteroids, as larger planetary bodies would have a stronger, counteracting gravitational pull.

Continue reading “MIT engineers test an idea for a new hovering rover” »

A team of MIT researchers has figured out a way to create a supercapacitor simply by mixing cement, the binding ingredient of concrete, and a fine charcoal product called carbon black together with water.

Better yet, this mixture could allow a home to store a full day’s worth of energy in its foundation, potentially paving the way to an efficient renewable energy storage solution that doesn’t rely on mining rare Earth metals.

Roads made up of the material could even power electric cars wirelessly, the researchers say, or windmills could store their generated energy in their base.

North Carolina State University researchers have discovered a new welding method for composite metal foam (CMF), preserving its light, strong, and thermally insulating properties, vital for numerous applications.

Researchers at North Carolina State University have now identified a welding technique that can be used to join composite metal foam (CMF) components together without impairing the properties that make CMF desirable. CMFs hold promise for a wide array of applications because the pockets of air they contain make them light, strong and effective at insulating against high temperatures.

Characteristics and Challenges of CMF.

Supernovae–stellar explosions as bright as an entire galaxy–have fascinated us since time immemorial. Yet, there are more hydrogen-poor supernovae than astrophysicists can explain. Now, a new Assistant Professor at the Institute of Science and Technology Austria (ISTA) has played a pivotal role in identifying the missing precursor star population. The results, now published in Science, go back to a conversation the involved professors had many years ago as junior scientists.

The Enigma of Hydrogen-Poor Supernovae

Continue reading “Supernova Scavenger Hunt: Cracking the Case of Cosmic Ghost Stars” »

A Tesla driver using the new Full Self-Driving (FSD) Beta v12 software managed to showcase a new behavior: FSD Beta autonomously looking for a parking spot.

The Tesla v12 software update is expected to introduce what CEO Elon Musk has been calling “end-to-end neural nets”. The biggest difference with previous FSD updates is that the vehicle’s controls would now be handled by neural nets rather than being coded by programmers.

It is being touted as the difference maker.