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Topic Review
3D-Printed Silica Glass
Glass technologies for 3D printing can be divided into several categories according to the printing method and the form of pre-treatment for the raw materials. These categories include powder-based, photopolymerization-based, and material extrusion-based 3D printing technology. Among them, fused deposition modeling (FDM), based on material extrusion (MEX), and selective laser sintering/melting (SLS/SLM), based on powder, usually require strict processing conditions and are therefore less suitable for laboratory processing. The most promising processing technologies are stereolithography (SLA), digital light processing (DLP), two-photon polymerization (TPP), sheet lamination (SL), which is based on photopolymerization, and DIW, based on MEX.
  • 1.8K
  • 28 Feb 2022
Topic Review
Liquid Mirror Telescope
Liquid mirror telescopes are telescopes with mirrors made with a reflective liquid. The most common liquid used is mercury, but other liquids will work as well (for example, low melting alloys of gallium). The liquid and its container are rotated at a constant speed around a vertical axis, which causes the surface of the liquid to assume a paraboloidal shape, suitable for use as the primary mirror of a reflecting telescope. The rotating liquid assumes the paraboloidal shape regardless of the container's shape. To reduce the amount of liquid metal needed, and thus weight, a rotating mercury mirror uses a container that is as close to the necessary parabolic shape as possible. Liquid mirrors can be a low cost alternative to conventional large telescopes. Compared to a solid glass mirror that must be cast, ground, and polished, a rotating liquid metal mirror is much less expensive to manufacture. Isaac Newton noted that the free surface of a rotating liquid forms a circular paraboloid and can therefore be used as a telescope, but he could not actually build one because he had no way to stabilize the speed of rotation. The concept was further developed by Ernesto Capocci of the Naples Observatory (1850), but it was not until 1872 that Henry Skey of Dunedin, New Zealand constructed the first working laboratory liquid mirror telescope. Another difficulty is that a liquid metal mirror can only be used in zenith telescopes, i.e., that look straight up, so it is not suitable for investigations where the telescope must remain pointing at the same location of inertial space (a possible exception to this rule may exist for a mercury mirror space telescope, where the effect of Earth's gravity is replaced by artificial gravity, perhaps by rotating the telescope on a very long tether, or propelling it gently forward with rockets). Only a telescope located at the North Pole or South Pole would offer a relatively static view of the sky, although the freezing point of mercury and the remoteness of the location would need to be considered. A very large telescope already exists at the South Pole, but the North Pole is located in the Arctic Ocean. The mercury mirror of the Large Zenith Telescope in Canada was the largest liquid metal mirror ever built. It had a diameter of six meters, and rotated at a rate of about 8.5 revolutions per minute. It is now decommissioned. This mirror was a test, built for $1 million but it was not suitable for astronomy because of the test site's weather. They are now planning to build a larger 8 meter liquid mirror telescope ALPACA for astronomical use and a larger project called LAMA with 66 individual 6.15 meter telescopes with a total collecting power equal to a 55 meter telescope, resolving power of a 70 meter scope.
  • 1.8K
  • 08 Oct 2022
Topic Review
Integrated OPAs for Beam Forming/Steering
Integrated optical phased arrays (OPAs) can be used for beam shaping and steering with a small footprint, lightweight, high mechanical stability, low price, and high-yield, benefiting from the mature CMOS-compatible fabrication. 
  • 1.7K
  • 18 Jun 2021
Topic Review
InN SAs for Ultrafast Lasers
New fabrication methods are strongly demanded for the development of thin-film saturable absorbers with improved optical properties (absorption band, modulation depth, nonlinear optical response). In this sense, we investigate the performance of indium nitride (InN) epitaxial layers with low residual carrier concentration (<1018 cm^-3), which results in improved performance at telecom wavelengths (1560 nm). These materials have demonstrated a huge modulation depth of 23% and a saturation fluence of 830 uJ/cm2, and a large saturable absorption around -3 x10^4 cm/GW has been observed, attaining an enhanced, nonlinear change in transmittance. We have studied the use of such InN layers as semiconductor saturable absorber mirrors (SESAMs) for an erbium (Er)-doped fiber laser to perform mode-locking generation at 1560 nm. We demonstrate highly stable, ultrashort (134 fs) pulses with an energy of up to 5.6 nJ.a
  • 1.7K
  • 01 Dec 2020
Topic Review
Allying Meta-Structures with Diverse Optical Waveguides for Integrated-Photonics
Recent years have witnessed tremendous interest in synergizing various functional subwavelength structures into diverse optical waveguide platforms to enable versatile photonic meta-devices. The advancement of meta-waveguides not only extends meta-optics into the manipulation of guided wave, but may also reshape the landscapes of photonic integrated circuits and massive emergent applications. A recent review paper outlined latest progress on meta-waveguides-based photonics devices and systems. Both forward and inverse designed scenarios are cataloged showcasing vibrant opportunities.
  • 1.7K
  • 13 Dec 2021
Topic Review
Optimizing Sustainability Opportunities for Biochar
Biochar is most commonly considered for its use as a soil amendment, where it has gained attention for its potential to improve agricultural production and soil health. Twenty years of near exponential growth in investigation has demonstrated that biochar does not consistently deliver these benefits, due to variables in biochar, soil, climate, and cropping systems. While biochar can provide agronomic improvements in marginal soils, it is less likely to do so in temperate climates and fertile soils. Here, biochar and its coproducts may be better utilized for contaminant remediation or the substitution of nonrenewable or mining-intensive materials. 
  • 1.7K
  • 18 Oct 2021
Biography
Waheed Arian
Waheed Arian (born 5 August 1983) is a British doctor and radiologist, born in Afghanistan, who founded a telemedicine charity called Arian Teleheal. The charity enables doctors in conflict zones and low resource countries to use their smartphones to receive advice from volunteer specialists in the UK, Canada, the US and other countries. Arian has won several international awards for his achieve
  • 1.7K
  • 12 Dec 2022
Topic Review
Near-Infrared Graphene/Silicon Photodetectors
In recent years, graphene has attracted much interest due to its unique properties of flexibility, strong light-matter interaction, high carrier mobility and broadband absorption. In addition, graphene can be deposited on many substrates including silicon with which is able to form Schottky junctions, opening the path to the realization of near-infrared photodetectors based on the internal photoemission effect where graphene plays the role of the metal.
  • 1.6K
  • 29 Oct 2020
Topic Review
Polarization Lidar
Traditional lidar techniques mainly rely on the backscattering/echo light intensity and spectrum as information sources. In contrast, polarization lidar (P-lidar) expands the dimensions of detection by utilizing the physical property of polarization. By incorporating parameters such as polarization degree, polarization angle, and ellipticity, P-lidar enhances the richness of physical information obtained from target objects, providing advantages for subsequent information analysis.
  • 1.6K
  • 12 Oct 2023
Topic Review
Quantum Rayleigh Annihilation of Entangled Photons and Quantum Local Realism
The interpretation of published experimental results intended to prove the existence of a quantum phenomenon of non-locality involving photonic entangled states did not take into consideration the existence of the quantum Rayleigh conversion of photons in dielectric media. This phenomenon leads to the existence of high levels of correlations between two independent photonic and linearly polarized quantum states generated after the entangled photons have been absorbed through the quantum Rayleigh conversion. Both pure and mixed individual states of polarization result in expressions normally associated with entangled photonic states, providing support for the view that the physical reality of quantum non-locality is highly questionable.
  • 1.6K
  • 28 Oct 2020
Topic Review
Waveguide-Enhanced Raman Spectroscopy
Photonic chip-based methods for spectroscopy are of considerable interest due to their applicability to compact, low-power devices for the detection of small molecules. Waveguide-enhanced Raman spectroscopy (WERS) has emerged over the past decade as a particularly interesting approach. WERS utilizes the evanescent field of a waveguide to generate Raman scattering from nearby analyte molecules, and then collects the scattered photons back into the waveguide. The large interacting area and strong electromagnetic field provided by the waveguide allow for significant enhancements in Raman signal over conventional approaches.
  • 1.6K
  • 29 Dec 2022
Topic Review
Optical Fiber Biochemical Sensors Based on Graphene
Graphene, a novel form of the hexagonal honeycomb two-dimensional carbon-based structural material with a zero-band gap and ultra-high specific surface area, has unique optoelectronic capabilities, promising a suitable basis for its application in the field of optical fiber sensing. Graphene optical fiber sensing has also been a hotspot in cross-research in biology, materials, medicine, and micro-nano devices in recent years, owing to prospective benefits, such as high sensitivity, small size, and strong anti-electromagnetic interference capability and so on. 
  • 1.5K
  • 20 Jun 2022
Topic Review
Multi-Color Light-Emitting Diodes
Multi-color light-emitting diodes (LEDs) with various advantages of color tunability, self-luminescence, wide viewing angles, high color contrast, low power consumption, and flexibility provide a wide range of applications including full-color display, augmented reality/virtual reality technology, and wearable healthcare systems.
  • 1.5K
  • 13 Feb 2023
Topic Review
V-HOE Based Solar Concentrators
The fundamental advantages of volume holographic optical elements are very appealing for lightweight and cheap solar concentrators applications and can become a valuable asset that can be integrated into solar panels. 
  • 1.5K
  • 10 Jun 2021
Topic Review
Metasurfaces for Sensing Applications
Photonic devices (sensors, in particular) require that an efficient dynamic control of light at nanoscale through field (electric or optical) variation using substitute low-loss materials. One such option may be plasmonic metasurfaces. Metasurfaces are arrays of optical antenna-like anisotropic structures (sub-wavelength size), which are designated to control the amplitude and phase of reflected, scattered and transmitted components of incident light radiation.
  • 1.5K
  • 11 Oct 2022
Topic Review
Fluorescence-Based Sensors for High-Temperature Monitoring
Fiber-optic high-temperature sensors are gradually replacing traditional electronic sensors due to their small size, resistance to electromagnetic interference, remote detection, multiplexing, and distributed measurement advantages. 
  • 1.5K
  • 17 Aug 2022
Topic Review
Lossy Mode Resonance-Based Fiber Optic Sensors
Fiber optic sensors (FOSs) based on the lossy mode resonance (LMR) technique have gained substantial attention from the scientific community. The LMR technique displays several important features over the conventional surface plasmon resonance (SPR) phenomenon, for planning extremely sensitive FOSs. Unlike SPR, which mainly utilizes the thin film of metals, a wide range of materials such as conducting metal oxides and polymers support LMR.
  • 1.5K
  • 21 Nov 2022
Topic Review
TiO2 Photocatalysis
Catalysis on TiO2 nanomaterials in the presence of H2O and oxygen plays a crucial role in the advancement of many different fields, such as clean energy technologies, catalysis, disinfection, and bioimplants. Photocatalysis on TiO2 nanomaterials is well-established and has advanced in the last decades in terms of the understanding of its underlying principles and improvement of its efficiency. 
  • 1.5K
  • 17 Jul 2023
Topic Review
Perovskite Quantum Dots
The excellent luminescence properties of perovskite quantum dots (PQDs), including wide excitation wavelength range, adjustable emission wavelength, narrow full width at half maximum (FWHM), and high photoluminescence quantum yield (PLQY), highly match the application requirements in emerging displays.
  • 1.5K
  • 14 Jul 2022
Topic Review
Enchroma
EnChroma lenses are glasses designed to improve and modify some aspects of color vision deficiency for color blind people. The glasses were invented by Dr. Donald McPherson in 2002. Wearing the glasses results in subtle differences when color blind people look longer and more carefully.
  • 1.5K
  • 17 Nov 2022
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