Search results for "Length"
showing 10 items of 2188 documents
Amorphous semiconductor-electrolyte junction
1987
Abstract The photoelectrochemical behaviour of amorphous anodic films on niobium (a-Nb 2 O 5 ) grown in a wide range of thicknesses (20 ⩽ d ox ⩽ 25 nm) is presented. The influence of the wavelength, light intensity and film thickness on the photocharacteristics of the a-Nb 2 O 5 /electrolyte junction is investigated. Expressions for the photocurrent curves under steady-state conditions are derived by assuming a variable efficiency of photocarrier generation and different distributions of the electrical potential inside the amorphous films. The influence of the light intensity on the photocharacteristics and the existence of a sub-band-gap photoresponse are explained by assuming a finite den…
Full field automated evaluation of the quarter wave plate retardation by phase stepping technique
2002
Quarter wave plates are optical elements commonly used in photoelasticity to obtain circularly polarized light. They divide the incident light field into two linearly polarized orthogonal components with a phase difference of a quarter of the light wavelength. Due to the tolerance in manufacturing, however, the actual phase shifting produced by the plates is affected by an error, which noticeably influences the photoelastic measurements performed by means of various automated methods. This paper presents a technique, based on the phase stepping method, for the full field automatic evaluation of the quarter wave plate error.
Can we use time-resolved measurements to get Steady-State Transport data for Halide perovskites?
2018
Time-resolved, pulsed excitation methods are widely used to deduce optoelectronic properties of semiconductors, including now also Halide Perovskites (HaPs), especially transport properties. However, as yet, no evaluation of their amenability and justification for the use of the results for the above-noted purposes has been reported. To check if we can learn from pulsed measurement results about steady-state phototransport properties, we show here that, although pulsed measurements can be useful to extract information on the recombination kinetics of HaPs, great care should be taken. One issue is that no changes in the material are induced during or as a result of the excitation, and anothe…
Photomicrography of skin by ultraviolet light.
1971
Skin sections superimposed on fine-grained photographic plates were exposed to ultraviolet light (2580 A wavelength). The images obtained, which reproduced the microanatomy of tissue in the process of ultraviolet photoabsorption, were studied under the microscope. Since absorption is proportional to the concentration of such biologically important chromophore-bearing substances as nueleoproteins and melanoproteins, the method gives information on the content and distribution of these substances in normal and altered tissue.
Responsivity measurements of N-on-P and P-on-N silicon photomultipliers in the continuous wave regime
2013
We report the electrical and optical comparison, in continuous wave regime, of two novel classes of silicon photomultipliers (SiPMs) fabricated in planar technology on silicon P-type and N-type substrate respectively. Responsivity measurements have been performed with an incident optical power from tenths of picowatts to hundreds of nanowatts and on a broad spectrum, ranging from ultraviolet to near infrared (340-820 nm). For both classes of investigated SiPMs, responsivity shows flat response versus the optical incident power, when a preset overvoltage and wavelength is applied . More in detail, this linear behavior extends up to about 10 nW for lower overvoltages, while a shrink is observ…
The liquid-argon scintillation pulseshape in DEAP-3600
2020
AbstractDEAP-3600 is a liquid-argon scintillation detector looking for dark matter. Scintillation events in the liquid argon (LAr) are registered by 255 photomultiplier tubes (PMTs), and pulseshape discrimination (PSD) is used to suppress electromagnetic background events. The excellent PSD performance of LAr makes it a viable target for dark matter searches, and the LAr scintillation pulseshape discussed here is the basis of PSD. The observed pulseshape is a combination of LAr scintillation physics with detector effects. We present a model for the pulseshape of electromagnetic background events in the energy region of interest for dark matter searches. The model is composed of (a) LAr scin…
Transmission of light in deep sea water at the site of the Antares neutrino telescope
2005
The ANTARES neutrino telescope is a large photomultiplier array designed to detect neutrino-induced upward-going muons by their Cherenkov radiation. Understanding the absorption and scattering of light in the deep Mediterranean is fundamental to optimising the design and performance of the detector. This paper presents measurements of blue and UV light transmission at the ANTARES site taken between 1997 and 2000. The derived values for the scattering length and the angular distribution of particulate scattering were found to be highly correlated, and results are therefore presented in terms of an absorption length lambda_abs and an effective scattering length lambda_sct^eff. The values for …
A precise photometric ratio via laser excitation of the sodium layer - I. One-photon excitation using 342.78 nm light
2020
The largest uncertainty on measurements of dark energy using type Ia supernovae is presently due to systematics from photometry; specifically to the relative uncertainty on photometry as a function of wavelength in the optical spectrum. We show that a precise constraint on relative photometry between the visible and near-infrared can be achieved in upcoming surveys (such as in LSST at the Vera C. Rubin Observatory) via a mountaintop-located laser source tuned to the 342.78 nm vacuum excitation wavelength of neutral sodium atoms. Using a high-power (500 W) laser modified from laser guide star studies, this excitation will produce an artificial star (which we term a "laser photometric ratio s…
Laser wavelength effects on the refractive index change of waveguides written by femtosecond pulses in silica glasses
2018
We investigate the influence of two fs-laser wavelengths (343 and 800 nm) on the induced refractive index change (Δn) of waveguides written in silica materials. Results show that Δn is higher for waveguides photo-inscribed with UV photons.
Skin chromophore mapping from multi-spectral laser line images
2020
Skin chromophore maps can be used for assessment of various skin malformations and early cancer diagnostics. Commercially available devices are bulky and expensive. We present two portable proof-of-concept device prototypes for multi-spectral laser line imaging with three (448 nm, 532 nm and 659 nm) and four (450 nm, 523 nm, 638 nm and 850 nm) wavelength laser illumination. Laser modules and special optics that ensure uniform light distribution over the region of interest have been exploited. Skin chromophore maps were calculated using Beer-Lambert law, considering light scattering properties in the skin and including photon path length evaluated from the directly measured photon-time-of-fl…