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Topic Review
Optical Phase Shifters
Optical phase shifters have the functionality to control the phase of light by a change in the effective refractive index. In a Si photonics platform, it is an essential part composing optical modulators as well as switches in Si photonics. The realization of a silicon optical phase shifter marked a cornerstone for the development of silicon photonics, and it is expected that optical interconnects based on the technology relax the explosive datacom growth in data centers. High-performance silicon optical modulators and switches, integrated into a chip, play a very important role in optical transceivers, encoding electrical signals onto the light at high speed and routing the optical signals, respectively. The development of the devices is continuously required to meet the ever-increasing data traffic at higher performance and lower cost.
  • 6.4K
  • 08 Jun 2021
Topic Review
Optical Parametric Oscillators and Raman Lasers
Optical parametric oscillators (OPOs) and Raman lasers are two nonlinear-based laser technologies that extend the spectral range of conventional inversion lasers. Power and brightness scaling of lasers are significant for many applications in industry, medicine, and defense. Considerable advances have been made to enhance the power and brightness of inversion lasers.
  • 558
  • 30 Jan 2022
Topic Review
Optical Fibre-Based Sensors
Optical fibre sensors are an essential subset of optical fibre technology, designed specifically for sensing and measuring several physical parameters. These sensors offer unique advantages over traditional sensors, making them gradually more valuable in a wide range of applications. They can detect extremely small variations in the physical parameters they are designed to measure, such as analytes in the case of biosensing.
  • 297
  • 06 Sep 2023
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. 
  • 844
  • 20 Jun 2022
Topic Review
Optical Diffraction Tomography
Optical Diffraction Tomography (ODT) is an emerging tool for label-free imaging of semi-transparent samples in three-dimensional space. Being semi-transparent, such objects do not strongly alter the amplitude of the illuminating field.
  • 2.1K
  • 28 Jan 2022
Topic Review
Optical Detection of Pathogenic Bacteria
The optical detection of pathogenic bacteria is a growing area of ongoing research for clinically-focused applications. Different modalities, like vibrational spectroscopy, fluorescence, scattering- and polarization-based systems, have the potential to provide information about the biomolecular and morphological characteristics of a species for sample identification and differentiation. Additionally, growth pattern recognition, single-cell versus biofilm formations, cell motility and viability, cell mutation, and antibiotic resistance status can be studied with various optical modalities, providing great potential for rapid characterization of disease-causing pathogens.
  • 765
  • 03 Dec 2020
Topic Review
Optical Coherence Angiography Imaging in Ocular Vascular Diseases
Optical coherence tomography angiography (OCTA) provides us with a non-invasive and efficient means of imaging anterior and posterior segment vasculature in the eye. OCTA has been shown to be effective in imaging diseases such as diabetic retinopathy, retinal vein occlusions, retinal artery occlusions, ocular ischemic syndrome and neovascularization of the iris. It is especially useful with depth-resolved imaging of the superficial, intermediate, and deep capillary plexi in the retina, which enables us to study and closely monitor disease progression and response to treatment. With further advances in technology, OCTA has the potential to become a more widely used tool in the clinical setting and may even supersede ocular angiography in some areas.
  • 1.4K
  • 29 Oct 2020
Topic Review
Operator
In physics, an operator is a function over a space of physical states onto another space of physical states. The simplest example of the utility of operators is the study of symmetry (which makes the concept of a group useful in this context). Because of this, they are very useful tools in classical mechanics. Operators are even more important in quantum mechanics, where they form an intrinsic part of the formulation of the theory.
  • 455
  • 24 Nov 2022
Topic Review
Onium Compound
In chemistry, an onium ion is a cation formally obtained by the protonation of mononuclear parent hydride of a pnictogen (group 15 of the periodic table), chalcogen (group 16), or halogen (group 17). The oldest-known onium ion, and the namesake for the class, is ammonium, NH+4, the protonated derivative of ammonia, NH3. The name onium is also used for cations that would result from the substitution of hydrogen atoms in those ions by other groups, such as organic radicals, or halogens; such as tetraphenylphosphonium, (C6H5)4P+. The substituent groups may be divalent or trivalent, yielding ions such as iminium and nitrilium. A simple onium ion has a charge of +1. A larger ion that has two onium ion subgroups is called a double onium ion, and has a charge of +2. A triple onium ion has a charge of +3, and so on. Compounds of an onium cation and some other negative ion are known as onium compounds or onium salts. Onium ions and onium compounds are inversely analogous to -ate ions and ate complexes:
  • 593
  • 16 Nov 2022
Topic Review
On Sizes and Distances
On Sizes and Distances (of the Sun and Moon) (Περὶ μεγεθῶν καὶ ἀποστημάτων [ἡλίου καὶ σελήνης], Peri megethon kai apostematon) is a text by the ancient Greek astronomer Hipparchus. It is not extant, but some of its contents have been preserved in the works of Ptolemy and his commentator Pappus of Alexandria. Several modern historians have attempted to reconstruct the methods of Hipparchus using the available texts.
  • 367
  • 20 Oct 2022
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