Broad-spectrum Light Source Research Articles

A comparison study of the degradative effects and safety implications of UVC and 405 nm germicidal light sources for endoscope storage

Storage of flexible endoscopes under germicidal ultraviolet (UVC) light has been associated with degradation of device material leading to failure and increased risk to patients. 405 nm germicidal light presents a possible alternative, potentially providing effective bacterial inactivation without material damage. Samples of endoscope material were exposed to UVC and 405 nm germicidal light sources and a broad spectrum light source control. Material properties were monitored using FTIR, AFM, contact angle and confocal microscopy. Significant changes were observed with samples exposed to the UVC source, with variations in FTIR spectra indicative of side chain scission, a decrease in contact angle from 82.6° to 61.4°, an increase in average surface roughness from 2.34 nm to 68.7 nm and visible cracking of the surface. In contrast samples exposed to the 405 nm light source showed little to no changes, with any variations being comparable to those seen on samples exposed to the broad spectrum control. Bacterial adhesion tests on samples showed an 86.8% increase in Pseudomonas aeruginosa adhesion on UVC exposed samples and no significant increase in adhesion with samples exposed to the other light sources. 405 nm germicidal light therefore potentially represents a safer alternative to UVC light for use in flexible endoscope storage.

Application of white light Fresnel diffractometry to film thickness measurement.

In this work we present the theoretical background and experimental procedure to measure the thickness of thin films by analyzing Fresnel diffraction patterns obtained from polychromatic illumination of phase-step samples. As examples of this technique, we measured the thicknesses of thin aluminum layers on glass substrates using three different broad-spectrum light sources. The results are in excellent agreement with independent interferometric measurements within less than 5% relative uncertainties.

Ultra-short longitudinal spatial coherence length of laser light with the combined effect of spatial, angular, and temporal diversity

We demonstrate ultra-high axial-resolution topography and tomography of multilayered objects using pseudo thermal light source, i.e., laser. The longitudinal spatial coherence (LSC) length of light was significantly reduced by synthesizing a pseudo thermal source with the combined effect of spatial, angular, and temporal diversity. Thus, generating a low spatially coherent (i.e., broad angular frequency spectrum) light source having narrow temporal frequency spectrum. The LSC length was reduced less than 10 μm using a very low magnification lens. Experimental results of optical sectioning of multilayer objects with high axial-resolution of the order of 4 μm was achieved which is comparable to broadband light source. The present system does not require any dispersion compensation optical system for biological samples as a highly monochromatic light source is used.

Photoinduced superconductivity in semiconductors

We show that optically pumped semiconductors can exhibit superconductivity. We illustrate this phenomenon in the case of a two-band semiconductor tunnel-coupled to broad-band reservoirs and driven by a continuous wave laser. More realistically, we also show that superconductivity can be induced in a two-band semiconductor interacting with a broad-spectrum light source. We furthermore discuss the case of a three-band model in which the middle band replaces the broad-band reservoirs as the source of dissipation. In all three cases, we derive the simple conditions on the band structure, electron-electron interaction, and hybridization to the reservoirs that enable superconductivity. We compute the finite superconducting gap and argue that the mechanism can be induced through both attractive and repulsive interactions and is robust to high temperatures.

Light dulls and darkens bird eggs.

Although egg color is generally consistent within individual birds and robust to environmental variation, recent evidence suggests a degree of susceptibility to environmental perturbation or modulation of egg color. Most of this variation manifests via the physiology of the laying female, but some direct impacts of the environment on laid eggs have also been discovered. Here we test whether light changes bird egg color and we quantify its effect, by subjecting variable blue-green eggs of Rüppell's weaver (Ploceus galbula) to a broad-spectrum light source under laboratory conditions, and measuring egg reflectance every few hours. Eggshells gradually decreased in reflectance across the entire measured wavelength spectrum of 250–800 nm. Reflectance peaks were disproportionately affected, such that the height decreased of both the blue-green peak and the smaller UV peak typical of blue-green eggs. The reflectance of lighter eggs was affected slightly more than that of darker eggs. These changes are similar to previous results for changes over long periods of time in darkness, suggesting that light might hasten the same process of pigment degradation that proceeds even without light. Comparison between the experimental light source and both sunlight and typical artificial lighting situations raises the possibility that significant color change might occur during incubation in some birds, but indicates that eggshell illumination in museums for short periods of study is unlikely to affect their color to a detectable extent. Additional research should be performed on eggs of other species and in other light environments, with an eye to an eventual generalized model of the effect of light on eggshell color.

Photobiological Interactions of Blue Light and Photosynthetic Photon Flux: Effects of Monochromatic and Broad‐Spectrum Light Sources

Photosynthesis (Pn) and photomorphogenesis (Pm) are affected by light quality, light intensity and photoperiod. Although blue light (BL) is necessary for normal development, it is less efficient in driving Pn than other wavelengths of photosynthetically active radiation. The effects of BL on Pm are highly species dependent. Here we report the interacting effects of BL and photosynthetic photon flux (PPF) on growth and development of lettuce, radish and pepper. We used light-emitting diode (LED) arrays to provide BL fractions from 11% to 28% under broad-spectrum white LEDs, and from 0.3% to 92% under monochromatic LEDs. All treatments were replicated three times at each of two PPFs (200 and 500 μmol m(-2) s(-1)). Other than light quality, environmental conditions were uniformly maintained across chambers. Regardless of PPF, BL was necessary to prevent shade-avoidance responses in radish and lettuce. For lettuce and radish, increasing BL reduced stem length, and for both species, there were significant interactions of BL with PPF for leaf expansion. Increasing BL reduced petiole length in radish and flower number in pepper. BL minimally affected pepper growth and other developmental parameters. Pepper seedlings were more photobiologically sensitive than older plants. Surprisingly, there were few interactions between monochromatic and broad-spectrum light sources.

Opaque intraocular lens implantation

We read with great interest the recent article by Lee et al,1 who described their clinical experience with three patients who underwent primary implantation of Morcher (Stuttgart, Germany) occlusive intraocular lenses (IOLs) across a variety of neuroophthalmic indications. We hope to offer some further insight into these clinical observations in the context of our ongoing research into occlusive IOLs. We feel such a discussion may be of benefit to ophthalmologists managing this group of patients.

Inability to perform posterior segment monitoring by scanning laser ophthalmoscopy or optical coherence tomography with some occlusive intraocular lenses in clinical use

To evaluate whether occlusive intraocular lenses (IOLs) produced by several manufacturers for clinical use equivalently transmit near-infrared (IR) light for scanning laser ophthalmoscopy (SLO) or optical coherence tomography (OCT) imaging. Nuffield Laboratory of Ophthalmology, Oxford University, United Kingdom. Evaluation of diagnostic test or technology. The study evaluated 6 black IOLs of 2 designs: 3 poly(methyl methacrylate) (PMMA) and 3 iris-claw anterior chamber IOLs. Each IOL was placed between a broad-spectrum white light source and a spectroradiometer to generate transmission spectra. Transmission in the near-IR range was examined using an 850 nm light-emitting diode. Scanning laser ophthalmoscopy or OCT imaging using Spectralis spectral-domain SLO or OCT was attempted through occlusive IOLs in a model eye. Artisan iris-claw and MS 612 PMMA occlusive IOLs totally occluded all wavelengths of light, including in the near IR range in which SLO and OCT imaging systems operate. It was not possible to capture SLO or OCT images through the iris-claw and PMMA occlusive IOLs in a model eye. Results suggest the property of near-IR transmission that permits SLO or OCT imaging through occlusive IOLs is restricted to the Morcher range of occlusive IOLs. Patients with non-near IR transmitting IOLs will not be able to receive detailed posterior segment monitoring with SLO or OCT. This finding may have a significant impact on preoperative occlusive IOL selection and the management of current patients with occlusive IOLs. No author has a financial or proprietary interest in any material or method mentioned.

SIRAD – Personal radiation detectors

Abstract SIRAD badge dosimeters provide a visual qualitative measurement of exposure to radiation for mid range dose exposure. This is performed using an active radiochromic dosimeter in a transparent window, combined into a badge assembly. When irradiated, the badges active window turns blue, which can be matched against the given colour chart for a qualitative assessment of the exposure received. Two peaks in the absorption spectra located at 617 nm and 567 nm were found. When analysed with a common computer desktop scanner, the optical density response of the film to radiation exposure is non-linear but reproducible. The net OD of the film was 0.21 when exposed to 50cGyand 0.31 at 200 cGy exposure when irradiated with a 6 MV x-ray energy beam and analysed using a broad spectrum light source. These values reduced when exposed with kilovoltage x-rays with an approximate 30% reducing in sensitivity at 50 kVp. The film provides an adequate measurement and visually qualitative assessment of radiation exposure for levels in the range of 0–50 cGy.

Occlusive IOLs for Intractable Diplopia Demonstrate a Novel Near-Infrared Window of Transmission for SLO/OCT Imaging and Clinical Assessment

Occlusive intraocular lens (IOL) implantation is an effective therapeutic option in patients with intractable diplopia, visual confusion, and unsightly leukocoria. However, their use has been restricted by concerns that inability to visualize the retina may prevent the diagnosis of important posterior pole diseases. In this study, transmission spectra of occlusive IOLs were defined as a basis for acquiring scanning laser ophthalmoscopy/optical coherence tomography (SLO/OCT) images. Fifteen IOLs of three designs were examined: black small and large PMMA and black Lotus (Morcher GmbH, Stuttgart, Germany). Each IOL was placed between a broad-spectrum white light source and a spectroradiometer, to generate transmission spectra for each lens and determine the cutoff wavelength. Transmission in the near-infrared (NIR) range was confirmed with an 850-nm LED. A model eye was implanted with occlusive IOLs, and SLO/OCT scans were acquired with seven clinical SLO/OCT imaging systems. Occlusive IOLs demonstrated high levels of transmission of NIR light. It was determined that most SLO/OCT scanners would achieve 99% to 100% transmission at their operational wavelengths of NIR light. Furthermore, all clinical SLO/OCT imaging systems were capable of imaging fine retinal features without attenuation through occlusive IOLs in a model eye. In this study, a novel NIR window of high-level transmission was identified across the occlusive IOLs with applications to SLO/OCT imaging and NIR-based clinical assessment. The ability to acquire high-quality SLO/OCT scans to detect posterior pole disease may fundamentally change the current view on occlusive IOLs and encourage their use in patients with intractable diplopia.

Achieving accurate radiochromic optical-CT imaging when using a polychromatic light source

Optical-CT performed with a broad spectrum light source can lead to inaccurate reconstructed attenuation coefficients (and hence dose) due to 'spectral warping' as the beam passes through the dosimeter. Some wavelengths will be attenuated more strongly than others depending on the absorption spectrum of the radiochromic dosimeter. A simulation was run to characterize the error introduced by the spectrum warping phenomena. Simulations of a typical dosimeter and delivered dose (6cm diameter, 2 Gy irradiation) showed reconstructed attenuation coefficients can be in error by >12% when compared to those obtained from a monochromatic scan. A method to correct for these errors is presented and preliminary data suggests that with the correction, polychromatic imaging can yield imaging results equal in accuracy to those of monochromatic imaging. The advantage is that polychromatic imaging may be less sensitive to prominent schlerring artefacts that are often observed in telecentric optical-CT scanning systems with tight bandwidth filters applied.

White LEDs as broad spectrum light sources for spectrophotometry: Demonstration in the visible spectrum range in a diode‐array spectrophotometric detector

Although traditional lamps, such as deuterium lamps, are suitable for bench-top instrumentation, their compatibility with the requirements of modern miniaturized instrumentation is limited. This study investigates the option of utilizing solid-state light source technology, namely white LEDs, as a broad band spectrum source for spectrophotometry. Several white light LEDs of both RGB and white phosphorus have been characterized in terms of their emission spectra and energy output and a white phosphorus Luxeon LED was then chosen for demonstration as a light source for visible-spectrum spectrophotometry conducted in CE. The Luxeon LED was fixed onto the base of a dismounted deuterium (D(2) ) lamp so that the light-emitting spot was geometrically positioned exactly where the light-emitting spot of the original D(2) lamp is placed. In this manner, the detector of a commercial CE instrument equipped with a DAD was not modified in any way. As the detector hardware and electronics remained the same, the change of the deuterium lamp for the Luxeon white LED allowed a direct comparison of their performances. Several anionic dyes as model analytes with absorption maxima between 450 and 600 nm were separated by CE in an electrolyte of 0.01 mol/L sodium tetraborate. The absorbance baseline noise as the key parameter was 5 × lower for the white LED lamp, showing clearly superior performance to the deuterium lamp in the available, i.e. visible part of the spectrum.

Concentric Ring Scanning Laser Ophthalmoscope Artifacts and Dysphotopsia in Diffractive Multifocal Pseudophakia

A 67-year-old woman had decreased visual acuity in her left eye and disturbing concentric ring dysphotopsias after bilateral implantation of ReSTOR (SN60D3; Alcon Laboratories, Inc., Fort Worth, TX) diffractive multifocal intraocular lenses (IOLs). Monochromatic (820-nm infrared and 488-nm red-free) scanning laser ophthalmoscopy (SLO) documented central retinal concentric ring patterns resembling the patient's drawings of her dysphotopsia, prompting investigation of the relationship of these phenomena. Similar SLO findings were present in four eyes of three additional ReSTOR pseudophakes without dysphotopsia, but absent in monofocal pseudophakes or phakic individuals. Optical analysis shows that concentric ring SLO imaging artifacts can be caused by coherent reflection of monochromatic laser radiation off the diffractive optical element on the IOL's anterior surface, whereas concentric ring dysphotopsias are due to diffraction or projection of broad spectrum light sources in ordinary environments. Thus, the IOL's diffractive optics is the origin of both concentric ring dysphotopsia and SLO artifacts, but diffraction or projection causes the visual phenomenon, whereas coherent reflection produces the imaging anomaly.

Full-field optical coherence tomography by achromatic phase shifting with a rotatinghalf-wave plate

An achromatic phase shifter with a rotating half-wave plate (HWP) and a full-field opticalcoherence tomography (FF-OCT) system based on it are presented. The novelconfiguration of this phase shifter in the FF-OCT system can achromaticallyprovide a phase shift of eight times the rotation angle of the HWP. The theoreticalcalculation of the phase shift and numerical analysis of the phase shift error,as well as the amplitude ratio, are conducted by means of Jones matrices. Theactual phase shift has also been measured to confirm the validity of the ‘8θ phase shift—HWProtation angle θ’ relation. The coherent image of a mirror has been obtained by using the Hariharanalgorithm to verify the phase shifter’s feasibility. Using traditional phase shiftingalgorithms, en-face images of a coin have been measured at different depths to illustrate thetomographic capability of this FF-OCT system. In comparison with other current systems,our design has several advantages, and high-resolution high-speed FF-OCT imaging can beenvisioned. The phase shifter can be used for common path setups and is verysuitable for implementing the phase shifting of a broad-spectrum light source.

Self-pulsing 1050 nm quantum dot edge emitting laser diodes

We examine self-pulsing, edge emitting, quantum dot laser diodes as continuous broad spectrum light sources emitting at ∼1050 nm. Devices are configured with split contacts. When operated without a saturable absorber, the laser emits a number of discrete narrow modes, which merge to form a broad continuous lasing spectrum on application of the saturable absorber. The broadened spectra are consistent with the modulated carrier density expected under Q-switched operation. This provides a simple technique for generating emission suitable for biomedical applications. The spectral width achieved is ∼10 nm, and the average output power is 7.5 mW.

A proposed in-vessel calibration light source for the Joint European Torus

An in-vessel calibration light source (ICLS) is proposed for use during extended shutdown periods of the Joint European Torus (JET). The ICLS is primarily a 12 in. integrating sphere (4 in. opening) with four lamps (of known radiance), which can be positioned inside the JET vacuum vessel via the remote handling arm during interventions in the JET operating schedule. This will facilitate the in situ calibration of optical diagnostics, which rely on absolute light intensity measurements currently made when the diagnostics are removed from JET. The ICLS could ultimately reduce/remove the mechanical stresses associated with the repositioning of diagnostics for calibration purposes. At least 10 diagnostic systems (approximately 20 diagnostic subsystems) could benefit from the ICLS; in some instances the ICLS provides the only viable absolute-calibration strategy. Moreover, the ICLS will be a broad-spectrum white light source, enabling intensity calibrations at all visible wavelengths. A secondary benefit of the ICLS is in its use as an illumination source for making measurements of the reflectance (over a broad spectral range and at multiple angles) from the tiles lining the JET vacuum vessel. During the ITER-like wall intervention new Be, C, and W tiles will be installed in JET and their reflectance measured. Measurements made in subsequent JET interventions will provide data on the effect of high-temperature plasma operation on the reflectance of these tiles.

Evidence‐based review of lasers, light sources and photodynamic therapy in the treatment of acne vulgaris

Background There is a considerable need for effective and safe treatment for acne vulgaris. Objective In a systematic review with an evidence-based approach to assess the effects of optical treatments for acne vulgaris. Methods Original publications of controlled clinical trials were identified through searches in PubMed and the Cochrane Library. Results A total of 16 randomized controlled trials (RCT) and 3 controlled trials (CT) were identified, involving a total of 587 patients. Interventions included photodynamic therapy (PDT; 5 RCTs), infrared lasers (4 RCTs), broad-spectrum light sources (3 RCTs, 1 CT), pulsed dye lasers (PDL; 2 RCTs, 1 CT), intense pulsed light (IPL; 1 RCTs, 2 CTs), and potassium titanyl phosphate laser (1 RCT). The randomization method was mentioned in 6 of 16 RCTs, and one trial described adequate allocation concealment. Most trials were intraindividual trials (12 of 19), which applied blinded response evaluations (12 of 19) and assessed a short-term efficacy up to 12 weeks after treatment (17 of 19). Based on the present best available evidence, we conclude that optical treatments possess the potential to improve inflammatory acne on a short-term basis with the most consistent outcomes for PDT [up to 68% improvement, aminolevulinic acid (ALA), methyl-aminolevulinic acid (MAL) and red light]. IPL-assisted PDT seems to be superior to IPL alone. Only two trials compare optical vs. conventional treatments, and further studies are needed. Side-effects from optical treatments included pain, erythema, oedema, crusting, hyperpigmentation, pustular eruptions and were more intense for treatments combined with ALA or MAL. Conclusion Evidence from controlled clinical trials indicates a short-term efficacy from optical treatments for acne vulgaris with the most consistent outcomes for PDT. We recommend that patients are preoperatively informed of the existing evidence, which indicates that optical treatments today are not included among first line treatments.

A white light confocal microscope for spectrally resolved multidimensional imaging

Spectrofluorometric imaging microscopy is demonstrated in a confocal microscope using a supercontinuum laser as an excitation source and a custom-built prism spectrometer for detection. This microscope system provides confocal imaging with spectrally resolved fluorescence excitation and detection from 450 to 700 nm. The supercontinuum laser provides a broad spectrum light source and is coupled with an acousto-optic tunable filter to provide continuously tunable fluorescence excitation with a 1-nm bandwidth. Eight different excitation wavelengths can be simultaneously selected. The prism spectrometer provides spectrally resolved detection with sensitivity comparable to a standard confocal system. This new microscope system enables optimal access to a multitude of fluorophores and provides fluorescence excitation and emission spectra for each location in a 3D confocal image. The speed of the spectral scans is suitable for spectrofluorometric imaging of live cells. Effects of chromatic aberration are modest and do not significantly limit the spatial resolution of the confocal measurements.

Laser- and light-based hair removal: an update

A variety of laser technologies are now able to successfully remove unwanted hair. Successful removal is based on an understanding of laser physics and appropriate wavelengths, pulse durations and cooling of the skin. Although ruby lasers were among the first to be used, alexandrite, diode and neodymium-doped yttrium aluminium garnet (Nd:YAG) lasers, as well as a variety of broad-spectrum intense pulsed light sources, are currently more commonly used for the treatment of unwanted hair. Darker skin types are more difficult to treat but can also be treated. Complications can occur after laser hair removal but can be reduced through an understanding of the fundamentals of laser removal. These complications include the obvious, such as scarring and pigmentary changes, and the not so obvious, such as reticulate erythema and uveitis. Laser hair removal is now widely accepted as a successful approach to remove unwanted hair in both men and women. The future will involve office-based laser and light source hair removal, as well as a variety of laser and light-based home devices.

Laser Induced Photocatalytic Splitting of Water Over WO3 Catalyst

The photocatalytic activity of WO 3 semiconductor powder for water splitting into H 2 and O 2 was studied. Instead of conventional broad spectrum light sources like lamps, monochromatic laser radiations in the UV region (γ = 355 nm) were used as the light source for the study of photocatalytic water splitting over WO 3 . An alternate route based upon the photo-chromic properties of WO 3 for the production of hydrogen was suggested. The effect of dissolved metal ions on H 2 and O 2 yield in the presence of various metal ions was also investigated. The effect of the hole-capture agent on H 2 and O 2 yield was also studied by using methanol as a hole-capture agent. The data on pH measurements during the course of reaction was found very useful in explaining the reaction mechanism in general, and metal ions action in particular.