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Light Wavelength (light + wavelength)
Selected AbstractsTheoretical and experimental study of polarization characteristics of polarization maintaining fiber based on wavelength-sweeping modulationMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 7 2010Zuo-Liang Duan Abstract We analyze theoretically the polarization characteristics of polarization maintaining fiber and study the basic measurement principles of beat length and polarization extinction ratio of this kind of optical fiber. According to the dependence of the phase difference between two orthogonally polarized modes (denoted as HE and HE) transmitted in the polarization maintaining fiber on the light wavelength, we propose the wavelength-sweeping modulation method to measure the beat length and the model birefringence. Based on this technique, the beat length and polarization extinction ratio of the PANDA polarization maintaining fibers (PMFs) (provided by Yangtze Optical Fiber and Cable Company, Wuhan, China) were investigated in detail. Experimental results show good consistent with the theoretical ones. We find that this method shows high measurement precision with the advantages of clear measurement principle and easy to operate. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1466,1469, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25244 [source] Hopping photoconductivity and its long-time relaxation in two-dimensional array of Ge/Si quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 8 2005N. P. Stepina Abstract Photoconductivity excitation kinetics has been studied in a two-dimensional array of Ge/Si quantum dots under illumination with different light wavelength. Both negative and positive photoeffects depending on dot occupations with holes were observed. Long-time conductivity dynamics (typically, 102,104 sec at T = 4.2 K) has been revealed as well as after switch on and switch off the illumination, displaying a sluggish temporal dependence. The observed effects were not suppressed by decreasing of the excitation energy below the silicon band-gap. For electronic glasses it was discovered that the more time under excitation the faster relaxation rate. Our results are explained by the different capture rate of electrons and holes by quantum dots, due to the presence of potential barriers created by positively charged Ge quantum dots. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Coherence length and time of excitons in ZnSe quantum wellsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2004B. Dal Don Abstract We investigate the in-plane transport of excitons in quantum wells by nano-photoluminescence. The experimental method is based on a confocal microscope with an enhanced resolution given by the introduction of a solid immersion lens. In combination with pulsed laser excitation and streak-camera detection, we have access to transport phenomena on a timescale faster than the time of scattering with acoustic phonons and a length scale of the light wavelength. We use ZnSe-based quantum wells as a model system since hot excitons with well defined excess energy can be formed assisted by the emission of optical phonons. This results e.g. in a periodic quenching of the excitonic transport length as function of excitation excess energy which, in comparison, is not found in GaAs quantum wells. Monte Carlo simulations of the nonlinear expansion of the luminescence spot observed as a function of time reveal the difference between the spatial profiles of the luminescence and the exciton density. The latter shows an oscillatory behaviour in time due to the dominant backscattering, when the first acoustic phonon is emitted. From this oscillation we can determine simultaneously the coherence time and length of the excitonic transport in ZnSe quantum wells. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Investigating the influence of wavelength, light intensity and macular pigmentation on retinal straylightACTA OPHTHALMOLOGICA, Issue 2009J ROZEMA Purpose To investigate the influence of wavelength, light intensity and macular pigmentation on retinal straylight. This will be tested in both phakic and pseudophakic eyes by means of color filters, as well as by comparing postoperative straylight results of eyes implanted with either clear or blue-blocking IOLs. It has also been suggested in the literature that the yellow macular pigment reduces the effects of the short wavelength components of retinal straylight. Methods In this prospective study the straylight is measured on two groups of pseudophakic subjects: one group of 25 subjects implanted with a clear IOL (Alcon AcrySof SA60AT) and another group of 25 subjects implanted with a yellow IOL (AcrySof Natural SN60AT) using white light as well as with blue, green and red filters. These measurements are repeated on a group of age matched 25 phakic subjects. All retinal straylight measurements will be performed using the Oculus C-Quant straylight meter. In the normal and clear IOL subjects the macular pigment is measured as well using the Tinsley M|Pod device. Results The first, preliminary results demonstrate that in healthy eyes the retinal straylight measured by the Oculus C-Quant depends on the wavelength of the stimulus light. Measurements performed with blue light were lower than those performed in green or red light. Conclusion Stimulus light wavelength appears to have an influence on straylight measurements. Further study on a larger population is required to confirm this trend and to study how IOL color may influence this result in pseudophakic eyes. The possible influence of macular pigment on retinal straylight will be studied simultaneously. [source] The use of light-emitting diode therapy in the treatment of photoaged skinJOURNAL OF COSMETIC DERMATOLOGY, Issue 3 2007FACCS, FRACGP, Fabien Baez MBBS, MAACS, MCPSA Summary Background, Light-emitting diode (LED) therapy is an increasingly popular methodology for the treatment of sun damage. Combination use of light wavelengths reported to stimulate collagen synthesis and accelerate fibroblast,myofibroblast transformation may display a composite rejuvenative effect. Objective, To clinically assess reduction in sun damage signs following a 5-week course of LED therapy and to assess subject's perception of the treatment. Methods, Thirteen subjects with wrinkles or fine lines in the periorbital and nasolabial region and those presenting Glogau scale photodamage grade II,III received nine 20-min duration light treatments using the OmniluxÔ LED system. The treatments combined wavelengths of 633 and 830 nm at fluences of 126 and 66 J/cm2, respectively. Sun-damage reduction was assessed at 6, 9, and 12 weeks by clinical photography and patient satisfaction scores. Results, The majority of subjects displayed "moderate" (50%) or "slight" (25%) response to treatment at investigator assessment. Treatment of the periorbital region was reported more effective than the nasolabial region. At 12-week follow-up, 91% of subjects reported improved skin tone, and 82% reported enhanced smoothness of skin in the treatment area. Conclusion, Good response to LED therapy has been shown in this modest sample. Larger trials are needed to assess optimum frequency of light treatments and overall treatment time. [source] Ultraviolet photofragmentation of biomolecular ionsMASS SPECTROMETRY REVIEWS, Issue 3 2009James P. Reilly Abstract Mass spectrometric identification of all types of molecules relies on the observation and interpretation of ion fragmentation patterns. Peptides, proteins, carbohydrates, and nucleic acids that are often found as components of complex biological samples represent particularly important challenges. The most common strategies for fragmenting biomolecular ions include low- and high-energy collisional activation, post-source decay, and electron capture or transfer dissociation. Each of these methods has its own idiosyncrasies and advantages but encounters problems with some types of samples. Novel fragmentation methods that can offer improvements are always desirable. One approach that has been under study for years but is not yet incorporated into a commercial instrument is ultraviolet photofragmentation. This review discusses experimental results on various biological molecules that have been generated by several research groups using different light wavelengths and mass analyzers. Work involving short-wavelength vacuum ultraviolet light is particularly emphasized. The characteristics of photofragmentation are examined and its advantages summarized. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 28:425,447, 2009 [source] Characterisation of rough reflecting substrates incorporated into thin-film silicon solar cellsPROGRESS IN PHOTOVOLTAICS: RESEARCH & APPLICATIONS, Issue 6 2006V. Terrazzoni Daudrix Abstract Four different categories of rough reflecting substrates as well as a single periodic grating are incorporated and tested within n-i-p type amorphous silicon (a-Si:H) solar cells. Each category is characterised by its own texture shape; dimensions were varied within the categories. Compared to flat reflecting substrates, gains in short-circuit current density (Jsc) up to 20% have been obtained on rough reflecting plastic substrates. As long as (1) the characteristic dimensions of the textures are lower than the involved light wavelengths, (2) the textures do not present any defects i.e. as long as they do not have large craters or bumps spread over the surface, the root mean square roughness (,RMS) as well as the ratio of average feature height to average period can be used to evaluate the gain in Jsc; if each category of randomly textured substrates is considered separately, the haze factor can be used to estimate ,RMS and thereby the gains in Jsc. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||