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Topic Review
Scanless and Detectorless Imaging System
Optical feedback interferometry is a versatile and robust technology for both sensing and imaging applications, available at all wavelengths were a semiconductor laser exists, from 270 nm to 120 μm. It can be easily adapted to fiber integrated systems and promises to be compatible also to silicon photonics.
  • 971
  • 18 Nov 2020
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. 
  • 956
  • 20 Jun 2022
Topic Review
Biosensing Using SERS Active Gold Nanostructures
Surface-enhanced Raman spectroscopy (SERS) has become a powerful tool for biosensing applications owing to its fingerprint recognition, high sensitivity, multiplex detection, and biocompatibility. This review provides an overview of the most significant aspects of SERS for biomedical and biosensing applications. 
  • 955
  • 01 Nov 2021
Topic Review
Wavefront shaping concepts in OCT
Optical coherence tomography (OCT) enables three-dimensional imaging with resolution on the micrometer scale. The technique relies on the time-of-flight gated detection of light scattered from a sample and has received enormous interest in applications as versatile as non-destructive testing, metrology and non-invasive medical diagnostics. However, in strongly scattering media such as biological tissue, the penetration depth and imaging resolution are limited. Combining OCT imaging with wavefront shaping approaches significantly leverages the capabilities of the technique by controlling the scattered light field through manipulation of the field incident on the sample.
  • 952
  • 24 Dec 2020
Biography
Md. Anowar Hossain
Engr. Md. Anowar Hossain is a specialized textile engineer (textile coloration & technical textiles), consultant (textile engineering), Professor (textile engineering), color philosopher, scientist, motivational speaker and a writer.                                                                                          Figure 1. Sketch of academi
  • 937
  • 15 Sep 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. 
  • 898
  • 10 Jun 2021
Topic Review
Generation/Amplification of Mid-Infrared Few-Cycle Pulse
The mid-infrared (MIR) wavelength is usually defined in the range of 2–20 μm (500–5000 cm−1). With its unique properties and wide application prospects, lasers in this band have attracted a great deal of attention from researchers all over the world.
  • 881
  • 30 Jul 2021
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.
  • 868
  • 03 Dec 2020
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.
  • 863
  • 13 Feb 2023
Topic Review
3D Live Cell Imaging Challenges
Relevant samples are described and various problems and challenges—including 3D Challenges of 3D imaging by optical sectioning, light scattering and phototoxicity—are addressed. Furthermore, enhanced methods of wide-field or laser scanning microscopy together with some relevant examples and applications are summarized. In the future one may profit from a continuous increase in microscopic resolution, but also from molecular sensing techniques in the nanometer range using e.g., non-radiative energy transfer (FRET).
  • 846
  • 23 Aug 2021
Topic Review
Photoacoustic Approach in the Characterization of Nanostructured Materials
The photoacoustic (PA) effect is the generation of pressure perturbations in a medium due to its heating with non-stationary electromagnetic radiation. A new generation of sensors can be engineered based on the sensing of several markers to satisfy the conditions of the multimodal detection principle. From this point of view, photoacoustic-based sensing approaches are essential. The photoacoustic effect relies on the generation of light-induced deformation (pressure) perturbations in media, which is essential for sensing applications since the photoacoustic response is formed due to a contrast in the optical, thermal, and acoustical properties. It is also particularly important to mention that photoacoustic light-based approaches are flexible enough for the measurement of thermal/elastic parameters. Moreover, the photoacoustic approach can be used for imaging and visualization in material research and biomedical applications. The advantages of photoacoustic devices are their compact sizes and the possibility of on-site measurements, enabling the online monitoring of material parameters. The latter has significance for the development of various sensing applications, including biomedical ones, such as monitoring of the biodistribution of biomolecules. To extend sensing abilities and to find reliable measurement conditions, one needs to clearly understand all the phenomena taking place during energy transformation during photoacoustic signal formation. 
  • 821
  • 21 Mar 2022
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.
  • 818
  • 11 Oct 2022
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. 
  • 799
  • 18 Oct 2021
Topic Review
Long-Wavelength Vertical-Cavity Surface-Emitting Lasers
Single-mode long-wavelength (LW) vertical-cavity surface-emitting lasers (VCSELs) present an inexpensive alternative to DFB-lasers for data communication in next-generation giga data centers, where optical links with large transmission distances are required. The use of long-wavelength (1300–1550 nm) single-mode (SM) VCSELs makes it possible to reduce the modal and chromatic dispersion in an optical link and, as a result, to extend its reach. Moreover, spatial division multiplexing (SDM) transmission by multicore fibers using long-wavelength (LW or short-wavelength infrared, SWIR) VCSELs are enabling many larger-scale data center networks than presently possible. 1300 nm VCSELs are of particularly strong importance for hybrid integration with silicon photonics, providing integrated modulators and InP- and GaAs-based integrated photonic circuits.
  • 794
  • 20 Mar 2023
Topic Review
Optical-Coherence Tomography Angiography in AMD
Optical coherence tomography angiography (OCTA) is a non-invasive diagnostic instrument that has become indispensable for the management of age-related macular degeneration (AMD). OCTA allows quickly visualizing retinal and choroidal microvasculature, and in the last years, its use has increased in clinical practice as well as for research into the pathophysiology of AMD.
  • 792
  • 22 Sep 2021
Biography
Chandrasekhara Venkata Raman
Chandrasekhara Venkata Raman, born on November 7, 1888, and passed away on November 21, 1970, was a distinguished Indian physicist renowned for his contributions to the study of light scattering. Alongside his student K. S. Krishnan, he developed a spectrograph and made a groundbreaking discovery – the modification of light scattering when it passes through a transparent material. This phenome
  • 792
  • 17 Feb 2024
Topic Review
Extinction-Coefficient Modulation of MoO3 Films
This entry focused on the application of the effective medium theory to describe the extinction coefficient (Qext) in molybdenum trioxide (MoO3) doped with different kinds of plasmonic nanoparticles, such as silver (Ag), gold (Au), and copper (Cu). Usually, in studies of these materials, it is normal to analyze the transmission or absorption spectra. However, the effect of this type or size of nanoparticles on the spectra is not as remarkable as the effect that is found by analyzing the Qext of MoO3. It was shown that the β-phase of MoO3 enhanced the intensity response of the Qext when compared to the α-phase of MoO3. With a nanoparticle size of 5 nm, the Ag-doped MoO3 was the configuration that presents the best response in Qext. On the other hand, Cu nanoparticles with a radius of 20 nm embedded in MoO3 was the configuration that presented intensities in Qext similar to the cases of Au and Ag nanoparticles. Therefore, implementing the effective medium theory can serve as a guide for experimental researchers for the application of these materials as an absorbing layer in photovoltaic cells. 
  • 785
  • 20 Aug 2021
Topic Review
Astrophotonic Spectrographs
Astrophotonics is the application of photonic technologies to channel, manipulate, and disperse light from one or more telescopes to achieve scientific objectives in astronomy in an efficient and cost-effective way. Utilizing photonic advantage for astronomical spectroscopy is a promising approach to miniaturizing the next generation of spectrometers for large telescopes. 
  • 783
  • 23 Jun 2021
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.
  • 759
  • 21 Nov 2022
Topic Review
OCT Applications in GI Tract
Optical coherence tomography (OCT) is uniquely poised for advanced imaging in the gastrointestinal (GI) tract as it allows real-time, subsurface and wide-field evaluation at near-microscopic resolution, which may improve the current limitations or even obviate the need of superficial random biopsies in the surveillance of early neoplasias in the near future. OCT’s greatest impact so far in the GI tract has been in the study of the tubular esophagus owing to its accessibility, less bends and folds and allowance of balloon employment with optimal contact to aid circumferential imaging. Moreover, given the alarming rise in the incidence of Barrett's esophagus and its progression to adenocarcinoma in the U.S., OCT has helped identify pathological features that may guide future therapy and follow-up strategy. This review will explore the current uses of OCT in the gastrointestinal tract and future directions, particularly with non-endoscopic office-based capsule OCT and the use of artificial intelligence to aid in diagnoses.
  • 728
  • 06 Nov 2020
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