Optical Radiation Research Articles

Physics of the Signal Formation in Photopletysmography: Assessment of the Contribution of Light Absorption and Scattering to the Registered Flux of Optical Radiation

The paper is devoted to the study of physical mechanisms of photoplethysmography (PPG) signal formation using Monte Carlo simulations of light transport in biological tissue. The problem of estimating the contribution of absorption and scattering variations to the registered PPG signal is solved. Based on a three-layer skin model, changes in the optical properties of the dermal layer (absorption and scattering) were sequentially simulated and their contributions to the total signal were estimated. Calculations were carried out for two wavelengths, 525 nm and 810 nm. It was found that for green light the main contribution to the signal formation is made by absorption (88 % versus 12 % scattering, respectively). While for the near infrared light, scattering predominates over absorption. In this case, the contributions of absorption and scattering are 28 % and 72 %. Thus, for the green wavelength range the classical volumetric model of signal formation is valid. Whereas for the near-infrared range, the predominant factor in signal formation is scattering of the medium, which can change due to processes such as changes in orientation, aggregation and deformation of red blood cells, their concentration in the diagnostic volume of tissue, etc.

Characterisation of optical waveguides for photonic integrated circuits

Fast signal processing at the speed of light is the main advantage of photonic integrated circuits. Therefore, these circuits have good prospects for the implementation of mathematical calculations, including matrix to vector multiplication. The purpose of the research was to create and investigate a technique for automatic measurement of brightness distribution along optical waveguides of analogue photonic integrated circuits. Empirical methods (observation, measurement, comparison, experiment) and a complex method (analysis and synthesis) have been used during the research. The proposed technique uses a digital camera that captures images of optical waveguide illuminated by light emitting diodes and image processing software to calculate brightness distribution. This technique determines the best approximation of this distribution, calculates parameters of brightness non-uniformity and losses of optical radiation. Measurements of a set of optical waveguides help to identify the best candidates for photonic integrated circuits. It has been found that optical waveguides with grinded surfaces acting as diffusive scattering have good combination of smooth brightness distribution and small losses of optical radiation. Due to multiple diffuse reflection and scattering within waveguide material, these waveguides are promising candidates for analogue photonic integrated circuits. All other waveguides with non-processed surface, with grooves or grinded with a large grain have sufficient losses of optical radiation. These losses are usually caused by the exit of optical radiation from waveguide surface. The obtained results are necessary for accurate design of circuits that takes into account scattering and losses in optical waveguides. The proposed technique can be applied in automatic technological process of manufacturing a fast and economical photonic matrix to vector multiplication, which does not require expensive electron-beam, optical or laser lithographic equipment

Recent Advances in Magnetically Actuated Droplet Manipulation for Biomedical Applications

The manipulation of droplets plays a vital role in biomedicine, chemistry, and hydromechanics, especially in microfluidics. Magnetic droplet manipulation has emerged as a prominent and advanced technique in comparison to other modes such as dielectric infiltration, optical radiation, and surface acoustic waves. Its notable progress is attributed to several advantages, including excellent biocompatibility, remote and non-contact control, and instantaneous response. This review provides a comprehensive overview of recent developments in magnetic droplet manipulation and its applications within the biomedical field. Firstly, the discussion involves an examination of the distinctive features associated with droplet manipulation based on both permanent magnet and electromagnet principles, along with a thorough exploration of the influencing factors impacting magnetic droplet manipulation. Additionally, an in-depth review of magnetic actuation mechanisms and various droplet manipulation methods is presented. Furthermore, the article elucidates the biomedical applications of magnetic droplet manipulation, particularly its role in diagnostic assays, drug discovery, and cell culture. Finally, the highlights and challenges of magnetic droplet manipulation in biomedical applications are described in detail.

Influence of titanium dioxide doping on the attenuation and optical characteristics of magnesium borate glass systems

This research examines the effects of varying titanium oxide (TiO2) concentrations in glass formulations, denoted as [(53-x)B2O3–7MgO–20BaF2–20Na2O-xTiO2] or BMBNTix, where x varies from 0 to 8 mol% in 2 % increments, on optical properties and radiation shielding effectiveness. Using MCNP5 (MC) Monte Carlo simulations and Phy-X software, this study assesses a range of photon energies from 0.015 to 15 MeV, focusing on key radiation shielding metrics such as the linear attenuation coefficient (μ), the half-value layer (HVL), and the tenth value layer (TVL). The results reveal a clear relationship between increased TiO2 levels in the BMBNTix glasses and improved radiation shielding performance. Notably, the linear attenuation coefficient (μ) steadily climbs from BMBNTi0 to BMBNTi8, highlighting the beneficial effect of a TiO2 addition to the material's ability to attenuate radiation. This trend is inversely mirrored in HVL values, which decrease from 0.010 cm for BMBNTi0 to 7.646 cm for BMBNTi8, reflecting enhanced shielding efficiency over the entire studied photon energy range. The effective atomic number (Zeff) also showcases a dynamic range from 40.793 to 15.101, suggesting a complex relationship between TiO2 content and photon interaction. Moreover, the study indicates a slight but consistent increase in the fast neutron removal cross-section (ΣR) from 0.104 cm−1 for BMBNTi0 to 0.106 cm−1 for BMBNTi8, pointing to improved neutron shielding with greater Ti and oxygen content in the glass. These insights highlight the potential of TiO2-enriched magnesium borate glasses as superior options for effective photon and neutron shielding, particularly in nuclear medicine, emphasizing their role in enhancing radiation safety measures.

From structure to luminescence investigation of B2O3-GeO2-BaO-ZnO glass doped with Dy3+

This study describes the preparation of Dy3+ doped B2O3-GeO2-BaO-ZnO (BGBZ) glass using a high temperature melting technique. By means of excitation and emission spectroscopy, it was determined that the glass sample with 25 mol% BaO content had the maximum luminous intensity. The internal structure of the glass was investigated using FT-IR spectroscopy, absorption spectrum testing, and J-O theoretical analysis in order to investigate the principle. The FT-IR spectrum revealed the coexistence of [BO3], [BO4], [GeO4], and [GeO6] coordination polyhedra. The Ω2 value reaching its maximum when the BaO content reached 25mol%, indicating the highest degree of asymmetry in the glass structure at that time. After analyzing the impact of BaO content on the glass structure, it was investigated how the concentration of Dy2O3 doping affected the glass's optical characteristics and radiation performance. By calculating the CIE of glass samples, it was found that the CCT value of glass sample 1.25Dy was 6735 K, suggesting that the produced glass may find use in the w-LED commercial industry. The 0.50Dy glass sample was calculated to have a high σse (8.47×10−22 cm2) from the emission spectral data, suggesting that the prepared glass sample may also be suitable for lasers.

Convolutional neural network-based classification of glaucoma using optic radiation tissue properties

BackgroundSensory changes due to aging or disease can impact brain tissue. This study aims to investigate the link between glaucoma, a leading cause of blindness, and alterations in brain connections.MethodsWe analyzed diffusion MRI measurements of white matter tissue in a large group, consisting of 905 glaucoma patients (aged 49-80) and 5292 healthy individuals (aged 45-80) from the UK Biobank. Confounds due to group differences were mitigated by matching a sub-sample of controls to glaucoma subjects. We compared classification of glaucoma using convolutional neural networks (CNNs) focusing on the optic radiations, which are the primary visual connection to the cortex, against those analyzing non-visual brain connections. As a control, we evaluated the performance of regularized linear regression models.ResultsWe showed that CNNs using information from the optic radiations exhibited higher accuracy in classifying subjects with glaucoma when contrasted with CNNs relying on information from non-visual brain connections. Regularized linear regression models were also tested, and showed significantly weaker classification performance. Additionally, the CNN was unable to generalize to the classification of age-group or of age-related macular degeneration.ConclusionsOur findings indicate a distinct and potentially non-linear signature of glaucoma in the tissue properties of optic radiations. This study enhances our understanding of how glaucoma affects brain tissue and opens avenues for further research into how diseases that affect sensory input may also affect brain aging.

Rapid optical switching of latched electrical resistance in a high-T c superconducting tape

We report microsecond timescale switching between the superconducting and normal states of commercially manufactured high-Tc superconducting wires using optical radiation to heat the conductor above Tc. The achieved voltages and switching times have significant implications for a new class of thermal switches. The report contains experimental data for photo-induced microsecond scale voltage transients as well as numerical analysis of heat propagation through the material in response to optical radiation. The microbridges are etched into commercially manufactured coated conductors and submerged in liquid nitrogen. By varying the magnitude of the transport current, two different optical responses are identified. At low transport currents, short-lived voltage transients occur, transitioning to persistent latching once the current is increased above a threshold value. The microbridge, therefore, behaves as a fast opening and closing switch when carrying low currents or an optically latched thyristor at high currents. This is understood to occur due to critical current suppression as a result of heating from the optical pulse. Optically induced heating reduces the superconducting volume fraction, and Joule heating due to the transport current interaction with the high temperature superconducting occurs, which either causes short-lived or stable self-heating normal regions dependent on the magnitude of the transport current. This study is concluded with an estimate of the energy necessary to drive the microbridge into the resistive state. The observed behavior can potentially be utilized as a switching element in superconducting transformer rectifiers where high frequency switch operation is required.

Direct Subcortical Stimulation for Intraoperative Mapping of Optic Radiations (P1-11.009)

Direct Subcortical Stimulation for Intraoperative Mapping of Optic Radiations (P1-11.009)

Electro-optic 3D snapshot of a laser wakefield accelerated kilo-ampere electron bunch

Laser wakefield acceleration, as an advanced accelerator concept, has attracted great attentions for its ultrahigh acceleration gradient and the capability to produce high brightness electron bunches. The three-dimensional (3D) density serves as an evaluation metric for the particle bunch quality and is intrinsically related to the applications of an accelerator. Despite its significance, this parameter has not been experimentally measured in the investigation of laser wakefield acceleration. We report on an electro-optic 3D snapshot of a laser wakefield electron bunch at a position outside the plasma. The 3D shape of the electron bunch was detected by simultaneously performing optical transition radiation imaging and electro-optic sampling. Detailed 3D structures to a few micrometer levels were reconstructed using a genetic algorithm. The electron bunch possessed a transverse size of less than 30 micrometers. The current profile shows a multi-peak structure. The main peak had a duration of < 10 fs and a peak current > 1 kA. The maximum electron 3D number density was ~ 9 × 1021 m -3. This research demonstrates a feasible way of 3D density monitoring on femtosecond kilo-ampere electron bunches, at any position of a beam transport line for relevant applications.

416 MRI Findings in Preterm Infants Associated with Strabismus

OBJECTIVES/GOALS: Prematurity and perinatal brain injury are known risk factors for strabismus. In this study, we sought to understand the link between neonatal neuroimaging measures in very preterm infants and the emergence of strabismus later in life. Study findings may inform if neonatal brain MRI could serve as a prognostic tool for this visual disorder. METHODS/STUDY POPULATION: This study draws from a longitudinal cohort of very preterm infants (VPT, &lt; 30 weeks gestation, range 23 – 29 weeks) who underwent an MRI scan at 36 to 43 weeks postmenstrual age (PMA). Anatomic and diffusion MRI data were collected for each child . A subset of thirty-three patients in this cohort had records of an eye exam, which were reviewed for a history of strabismus. Patients with MRI scans demonstrating cystic periventricular leukomalacia or grade III/IV intraventricular hemorrhage were classified as having brain injury. Clinical variables with a known association to strabismus or diffusion metrics were included in a multivariable logistic regression model. Diffusion tractography metrics were screened for association with strabismus on univariable analysis prior to inclusion in the regression model. RESULTS/ANTICIPATED RESULTS: A total of 17/33 (51.5%) patients developed strabismus. A logistic regression model including gestational age, PMA at MRI, retinopathy of prematurity (ROP) stage, brain injury, and fractional anisotropy of the right optic radiation was significant at the .001 level according to the chi-square statistic. The model predicted 88% of responses correctly. Each decrease of 0.01 in the fractional anisotropy of the right optic radiation increased the odds of strabismus by a factor of 1.5 (95% CI 1.03 – 2.06; p = .03). Patients with brain injury had 15.8 times higher odds of strabismus (95% CI 1.1 – 216.5; p = .04). Gestational age (OR 1.7; 95% CI 0.9 – 3.3; p = .1) and stage of ROP (OR 0.6; 95% CI 0.2 – 2.0; p = .4) were not significant predictors of strabismus in the multivariable model. DISCUSSION/SIGNIFICANCE: Our findings suggest that strabismus in VPT patients may be related to specific changes in brain structure in the neonatal period. The identified association between neonatal optic radiation microstructure and strabismus supports the possibility of using brain MRI in very preterm infants to prognosticate visual and ocular morbidity.

Comparison of Optical Properties and Radiation Stability of Gd2O3 Micro- and Nanopowders

Comparison of Optical Properties and Radiation Stability of Gd2O3 Micro- and Nanopowders

Lithium magnesium borosilicate glass: the impact of alternate doping with nano copper oxide and nano hematite on its structural, optical, and nuclear radiation shielding characteristics

Lithium magnesium borosilicate glass: the impact of alternate doping with nano copper oxide and nano hematite on its structural, optical, and nuclear radiation shielding characteristics

Intraventricular meningioma resection and visual outcomes.

Intraventricular meningiomas (IVMs) of the lateral ventricle are rare tumors that present surgical challenges because of their deep location. Visual field deficits (VFDs) are one risk associated with these tumors and their treatment. VFDs may be present preoperatively due to the tumor and mass effect (tumor VFDs) or may develop postoperatively due to the surgical approach (surgical VFDs). This institutional series aimed to review surgical outcomes following resection of IVMs, with a focus on VFDs. Patients who received IVM resection at one academic institution between the years 1996 and 2021 were retrospectively reviewed. Diffusion tensor imaging (DTI) reconstructions of the optic radiations around the tumor were performed from preoperative IVM imaging. The VFD course and resolution were documented. Thirty-two adult patients underwent IVM resection, with gross-total resection in 30 patients (93.8%). Preoperatively, tumor VFDs were present in 6 patients, resolving after surgery in 5 patients. Five other patients (without preoperative VFD) had new persistent surgical VFDs postoperatively (5/32, 15.6%) that persisted to the most recent follow-up. Of the 5 patients with persistent surgical VFDs, 4 received a transtemporal approach and 1 received a transparietal approach, and all these deficits occurred prior to regular use of DTI in preoperative imaging. New surgical VFDs are a common neurological deficit after IVM resection. Preoperative DTI may demonstrate distortion of the optic radiations around the tumor, thus revealing safe operative corridors to prevent surgical VFDs.

1230 Intraventricular Meningioma Resection and Visual Outcomes

INTRODUCTION: Intraventricular meningiomas (IVMs) of the lateral ventricle are rare tumors that present surgical challenges due to their location. Visual field deficits (VFDs) are one risk associated with these tumors and their treatment. VFDs may be present preoperatively due to the tumor and mass effect (i.e. tumor-VFDs) or may develop postoperatively due to the surgical approach (surgical-VFDs). METHODS: Patients who received IVM resection at one academic institution (1996-2021) were retrospectively reviewed. Diffusor tensor imaging (DTI) reconstructions of the optic radiations around the tumor were performed from preoperative imaging. VFD course and resolution were documented. A systematic review was conducted for studies on surgical resection for IVMs that included &gt;5 patients and reported postoperative neurologic outcomes. RESULTS: In the institutional series, thirty-two adult patients underwent IVM resection, with gross total resection in 30 patients (93.8%). Pre-operatively, tumor-VFDs were present in 6 patients, resolving after surgery in 5. Five other patients (without pre-operative VFD) had new persistent surgical-VFDs postoperatively (5/32 patients, 15.6%) that persisted to most recent follow-up. Of the 5 patients in the institutional cohort with persistent surgical-VFD, 4 had trans-temporal and 1 had a trans-parietal approach, and all of these occurred prior to regular use of DTI in preoperative imaging. In the systematic review, 14 studies met inclusion criteria and 12 commented on visual outcomes postoperatively. Median rate of tumor-VFDs improving postoperatively was 50% (range 0 to 100%) and median rate of new postoperative surgical-VFDs was 11% (range 0 to 23%). CONCLUSIONS: Half of presenting tumor-VFDs from IVMs improve with surgery. However, new surgical-VFDs are a common neurologic deficit after IVM resection. Preoperative DTI may demonstrate distortion of the optic radiations around the tumor, thus revealing safe operative corridors to prevent surgical-VFDs.

One Hundred Years of Relative Spectral Luminous Efficiency Curve – CIE V(λ) Function

In 1924, the International Commission on Illumination adopted the function of relative spectral luminous efficiency V(λ), which made it possible to move from subjective methods for assessing light sources of radiation to objective methods for measuring light quantities, constructing a system of light quantities, and creating standards for reproducing units of light quantities. Research in the field of physiological perception of light has continued and continues throughout these hundred years. This article is devoted to a brief review of materials from studies of actinic properties of the visual apparatus, i.e. spectral weighting functions of human perception of optical radiation, taking into account adaptation to various lighting conditions, as well as taking into account studies of fundamental physiological reactions of the visual system.

Cladding-pumped laser and amplifier for E- and S-bands based on multimode bismuth-doped graded-index fibers: toward "watt-level" output power.

In this Letter, we investigated the potential scalability of output power of a cladding-pumped laser and a power amplifier (booster) based on a multimode Bi-doped fiber (BDF) using the mode-selection approach. We fabricated the multimode double-clad graded-index (GRIN) fiber with a confined Bi-doped germanosilicate glass core with a diameter of ≈30 and ≈60 µm. Using femtosecond (fs) inscription technology with high spatial resolution, Bragg gratings of a special transverse structure allowing the selection of low-order modes were written into the core of BDFs. The operation features of the cladding-pumped multimode bismuth-doped GRIN fiber lasers with the inscribed Bragg gratings with various reflection coefficients were investigated. In addition, the behavior of the output power and the beam quality (M2 parameter) of the optical radiation of the developed devices was studied. The CW laser and booster operating at nearly 1.45 µm with maximum output powers of ≈0.8 and ≈1 W, respectively, based on the 60-µm-core BDF under pumping by multimode laser diodes at 808 nm were developed, which are, to the best of our knowledge, the most powerful cladding-pumped BDF devices to date. Near single-mode lasing (M2 <1.3) is demonstrated for a 30-µm-core fiber. The experimental data open new possibilities to achieve higher powers in cladding-pumped BDF sources, which are more cost-effective compared to core-pumped counterparts.

Central visual pathways affected by degenerative retinal disease before and after gene therapy.

Genetic diseases affecting the retina can result in partial or complete loss of visual function. Leber's congenital amaurosis (LCA) is a rare blinding disease, usually inherited in an autosomally recessive manner, with no cure. Retinal gene therapy has been shown to improve vision in LCA patients caused by mutations in the RPE65 gene (LCA2). However, little is known about how activity in central visual pathways is affected by the disease or by subsequent gene therapy. Functional MRI (fMRI) was used to assess retinal signal transmission in cortical and subcortical visual structures before and 1 year after retinal intervention. The fMRI paradigm consisted of 15-s blocks of flickering (8 Hz) black and white checkerboards interleaved with 15 s of blank (black) screen. Visual activation in the brain was assessed using the general linear model, with multiple comparisons corrected using the false discovery rate method. Response to visual stimulation through untreated eyes of LCA2 patients showed heightened fMRI responses in the superior colliculus and diminished activities in the lateral geniculate nucleus (LGN) compared to controls, indicating a shift in the patients' visual processing towards the retinotectal pathway. Following gene therapy, stimuli presented to the treated eye elicited significantly stronger fMRI responses in the LGN and primary visual cortex, indicating some re-engagement of the geniculostriate pathway (GS) pathway. Across patients, the post-treatment LGN fMRI responses correlated significantly with performance on a clinical test measuring light sensitivity. Our results demonstrate that the low vision observed in LCA2 patients involves a shift in visual processing toward the retinotectal pathway, and that gene therapy partially reinstates visual transmission through the GS pathway. This selective boosting of retinal output through the GS pathway and its correlation to improved visual performance, following several years of degenerative retinal disease, is striking. However, while retinal gene therapy and other ocular interventions have given hope to RPE65 patients, it may take years before development of therapies tailored to treat the diseases in other low vision patients are available. Our demonstration of a shift toward the retinotectal pathway in these patients may spur the development of new tools and rehabilitation strategies to help maximize the use of residual visual abilities and augment experience-dependent plasticity.

Spectroscopic and electrical properties of europium doped bismuth antimony fluoroborate glasses

Strong luminescence in the red spectral region is a well-known characteristic of the trivalent europium ion (Eu3+). We investigate a novel europium doped glassy substance for their use in optical devices, optoelectronics and radiation shielding. By using the traditional melt quenching technique, Bismuth antimony fluoroborate glasses are synthesized. XRD investigations support the amorphous nature of the material. Spectral measurements of absorption, photoluminescence (PL) excitation, PL emission, and PL decay curve are made in order to study the lasing properties. Judd-Ofelt (J-O) intensity parameters, from emission spectra, exhibit the trend Ω2> Ω4 furthermore used to find the radiative parameters-transition probability (AR), branching ratio (βR), radiative lifetime (τR), and stimulated emission cross-section (σse) for all the glasses. Decay curves show single exponential behavior and is used to find the quantum efficiency of the prepared glasses. The dielectric properties (dielectric constant (ɛ′), dielectric loss (ɛ″)), impedance and electrical conductivity (σac) of these glasses with variation in frequency have also been studied at the ambient temperature. The radiation shielding properties are evaluated for the photon energy range (1 keV–15 MeV). Based on the trends noticed in the radiative parameters, electrical conductivities and radiation shielding parameters, the present glasses could be found useful as optoelectronic devices, non-linear optical materials, battery anode materials and radiation shielding purposes.

Multiple-pathways light modulation in Pleurosigma strigosum bi-raphid diatom.

Ordered, quasi-ordered, and even disordered nanostructures can be identified as constituent components of several protists, plants and animals, making possible an efficient manipulation of light for intra- and inter- species communication, camouflage, or for the enhancement of primary production. Diatoms are ubiquitous unicellular microalgae inhabiting all the aquatic environments on Earth. They developed, through tens of millions of years of evolution, ultrastructured silica cell walls, the frustules, able to handle optical radiation through multiple diffractive, refractive, and wave-guiding processes, possibly at the basis of their high photosynthetic efficiency. In this study, we employed a range of imaging, spectroscopic and numerical techniques (including transmission imaging, digital holography, photoluminescence spectroscopy, and numerical simulations based on wide-angle beam propagation method) to identify and describe different mechanisms by which Pleurosigma strigosum frustules can modulate optical radiation of different spectral content. Finally, we correlated the optical response of the frustule to the interaction with light in living, individual cells within their aquatic environment following various irradiation treatments. The obtained results demonstrate the favorable transmission of photosynthetic active radiation inside the cell compared to potentially detrimental ultraviolet radiation.

A clinico-anatomical dissection of the magnocellular and parvocellular pathways in a patient with the Riddoch syndrome

Key messageThe Riddoch syndrome is thought to be caused by damage to the primary visual cortex (V1), usually following a vascular event. This study shows that damage to the anatomical input to V1, i.e., the optic radiations, can result in selective visual deficits that mimic the Riddoch syndrome. The results also highlight the differential susceptibility of the magnocellular and parvocellular visual systems to injury. Overall, this study offers new insights that will improve our understanding of the impact of brain injury and neurosurgery on the visual pathways.The Riddoch syndrome, characterised by the ability to perceive, consciously, moving visual stimuli but not static ones, has been associated with lesions of primary visual cortex (V1). We present here the case of patient YL who, after a tumour resection surgery that spared his V1, nevertheless showed symptoms of the Riddoch syndrome. Based on our testing, we postulated that the magnocellular (M) and parvocellular (P) inputs to his V1 may be differentially affected. In a first experiment, YL was presented with static and moving checkerboards in his blind field while undergoing multimodal magnetic resonance imaging (MRI), including structural, functional, and diffusion, acquired at 3 T. In a second experiment, we assessed YL’s neural responses to M and P visual stimuli using psychophysics and high-resolution fMRI acquired at 7 T. YL’s optic radiations were partially damaged but not severed. We found extensive activity in his visual cortex for moving, but not static, visual stimuli, while our psychophysical tests revealed that only low-spatial frequency moving checkerboards were perceived. High-resolution fMRI revealed strong responses in YL's V1 to M stimuli and very weak ones to P stimuli, indicating a functional P lesion affecting V1. In addition, YL frequently reported seeing moving stimuli and discriminating their direction of motion in the absence of visual stimulation, suggesting that he was experiencing visual hallucinations. Overall, this study highlights the possibility of a selective loss of P inputs to V1 resulting in the Riddoch syndrome and in hallucinations of visual motion.