Composite structure Al_(2)O_(3)/Al_(2)O_(3)-YAG:Ce/YAG ceramics with high color spatial uniformity for white laser lighting

Composite ceramic phosphor(CCP)is a candidate light-conversion material to obtain the high-quality laser lighting source.Phosphors based on the transmissive configuration model could not simultaneously meet the requirements of angular color uniformity and high thermal stability.In this study,a novel composite structure ceramic was designed,including Al_(2)O_(3)-YAG:Ce/YAG layered ceramic with a size of 1 mm×1 mm for lighting,and Al_(2)O_(3) ceramic(φ=16.0 mm)was used as the wrapping material due to its outstanding thermal stability.The prepared ceramics exhibited excellent thermal performance and no yellow ring phenomenon.Through this design,we achieved the match of the intensity distribution of the blue and yellow lights,resulting in a high angular color uniformity of 0.9 with a view angle of±80°.All ceramics showed no luminous saturation phenomenon,even the laser power density was increased up to 47.51 W/mm^(2).A high-brightness white-light source with a luminous flux of 618 lm,a luminous efficiency of 126 lm/W,a CCT of 6615 K,and a CRI of 69.9 was obtained in the transmissive configuration.In particular,the surface temperature of the ceramic was as low as 74.1℃ under a high laser radiation(47.51 W/mm^(2)).These results indicate that Al_(2)O_(3)/Al_(2)O_(3)-YAG:Ce/YAG composite structure ceramic is a promising luminescent material in the high-power laser lighting applications.

Cyan-green-emitting Ca_(3)Sc_(2)Si_(3)O_(12):Ce^(3+)transparent ceramics:A promising color converter for high-brightness laser lighting

Transparent phosphor ceramics have received increasing attention for high-brightness laser lighting,but commercially available phosphor ceramics are currently mainly limited to yellow YAG:Ce and green LuAG:Ce garnets,leaving a“cyan cavity”which is an obstacle to realizing full-color lighting.Achieving new phosphor ceramics capable of filling the cavity is a challenge.Herein,for the first time,cyan-green-emitting Ca_(3)Sc_(2)Si_(3)O_(12):Ce^(3+)(CSS:Ce)transparent ceramics have been successfully developed by two-step sintering technique under vacuum.The as-prepared CSS:Ce ceramics present high relative density of 99.7%and optical transmittance of 71%in the cyan-green spectral region.It exhibits an efficient band emission peaking at 504 nm(under 450 nm excitation)with internal/external quantum efficiency of 91%/62%.Furthermore,it has excellent thermal stability with a thermal quenching temperature(T_(0.5))of 838 K,approximately 100 K higher than that of LuAG:Ce ceramics(738 K).In addition,the CSS:Ce ceramics can withstand blue laser density of 45.6 W/mm^(2)and meanwhile generates cyan-green light with a forward luminous flux of 813 lm and forward luminous efficacy of 162 lm/W.The CSS:Ce transparent ceramics exhibit excellent luminescence performance comparable to the commercial LuAG:Ce ceramics and could be a highly promising color converter for high-brightness laser lighting.

Laser spot associated high-saturation phosphor-in-glass film for transmissive and reflective high-brightness laser lighting

Phosphor-in-glass(PiG)film is a promising luminescent material in high-brightness laser lighting for its advantages of high efficiency,outstanding color quality,and low-cost preparation,which must bear high laser power(LP)and laser power density(LPD)simultaneously to enable high-luminance light.Herein,laser spot associated high-saturation PiG film was proposed for transmissive and reflective high-brightness laser lighting.Two types of PiG films were prepared by printing and sintering La_(3)Si_(6)N_(11):Ce^(3+)(LSN)phosphor-borosilicate glass pastes on a sapphire substrate(PiG-S)and an AlN substrate(PiG-A),respectively.The PiG films with perfect crystal structure of phosphor were reliably bonded on the substrates.The effects of laser spot areas on the luminescence saturation of LP and LPD were investigated in the PiG films.With the increase of laser spot area from 0.5 to 2.5 mm^(2),the LP threshold of PiG films is gradually raised,while the LPD threshold of PiG films is decreased.The PiG-S withstands a high LP of 23.46 W and a high LPD of 20.64 W/mm^(2),enabling white light with a luminous flux of 3677 lm.The PiG-A withstands a high LP of 41.12 W and a high LPD of 35.56 W/mm^(2),enabling white light with a luminous flux of 2882 lm.Moreover,the PiG-A maintains lower working temperature compared with the PiG-S,and the temperatures reduce with the increasing laser spot area.The results demonstrate that the laser spot associated PiG films realize high saturation thresholds of LP and LPD simultaneously,and enable high luminance for laser lighting.

Ce:GdYAG phosphor-in-glass:An innovative yellow-emitting color converter for solid-state laser lighting

Stable,efficient and high color rendering index all-inorganic color converters are urgently demanded for white laser diodes.Phosphor-in-glass(PiG),possessing the advantages of phosphors excellent quantum efficiency as well as favorable chemical and thermal stability of glass,has attracted widespread attention.There have been only very few reports of Y_(1.31)Ce_(0.09)Gd_(1.6)Al_(5)O_(12)(Ce:GdYAG)PiG for solid-state laser light-ing.Herein,a series of Ce:GdYAG PiG samples are fabricated by a simple solid-state sintering method.Impressively,the supreme internal quantum efficiency of as-prepared PiG is 91%,which is very close to original phosphors(95%).Furthermore,PiG exhibits a high thermal conductivity(1.844 W m^(−1)K^(−1))and a maximum transparency(62%).Remarkably,by changing the concentration of phosphors and the thickness of PiG samples,a luminous efficacy of 163.5 lm/W,high color rendering index of 74.8 and low correlated color temperature of 4806.8 K are achieved under blue laser irradiation.These results indicate that the Ce:GdYAG PiG samples have shown tremendous application foreground as all-inorganic color converter for solid-state laser lighting.

Progress of laser and light treatments for lower eyelid rejuvenation

Laser and light treatments have recently become popular owing to its efficacy in treating laxity,rhytids,hyperpigmentation of the lower eyelids,and drooping of septum fat.For several decades,our department has explored the application of laser and light treatment for eye rejuvenation.This paper summarizes common treatment methods and analyzes the published literature on the indications and outcomes of multiple laser and light treatments for lower eyelid rejuvenation.An extensive survey of peer-reviewed literature was performed using PubMed,with the search terms“noninvasive treatment”,“infraorbital”,“palpebral bags”,“lower eyelid”,“radiofrequency(RF)”,“laser”,“nonsurgical skin tightening”,and“noninvasive fat reduction”.The results showed that the use of lasers,intense pulsed light(IPL),monopolar RF,bipolar RF,AdipoLASER rejuvenation(ALJ),and fractional RF microneedling are safe and effective treatments for palpebral bags.We conclude that using Qswitched lasers,IPL,RF,ALJ,and fractional RF microneedling is safe and effective for lower eyelid rejuvenation,with minimal complications and quick recovery.Further research and development of optoelectronic therapy may encourage breakthroughs in lower eyelid treatment,such as simplified complex surgery and noninvasive methods.

The division and bending of green and red semiconductor laser light at the same time

In this experimental study, the laser light was split and bended using a specially designed glass lenses at the same time. This process has been done at the atmospheric pressure and room temperature conditions. During the experiments, the semiconductor laser as a source of green and red laser diode is used. In addition, polari- zation, magnetic field, electric field or any other auxiliary materials and systems which affect laser light are not used to bend the laser light. Only transparent glass lenses that are designed specially are used in the experimental study.

Roughness Control of Layer-by-Layer and Alternative Spray Films from Congo Red and PAH via Laser Light Irradiation

Films from congo red (CR) alternated with poly(allylamine hydrochloride), PAH, were prepared by layer-by-layer and alternative spray techniques. In order to investigate the change of roughness induced by laser light irradiation (532 nm), both kinds of films were characterized by using UV-visible spectroscopy and atomic force microscopy (AFM). At dif- ferent irradiation times, layer-by-layer, LbL, films showed small changes in the roughness and irregular behavior, whereas spray films exhibited higher and a regular decreasing of roughness with increasing irradiation time. The higher roughness of spray films as compared with the LbL ones was attributed to different formation mechanisms of the films. The decreasing of the roughness as a function of the irradiation time (exhibited by the spray films) was associated to surface relaxation due to the interplay between photoisomerization of congo red dye and the heating of the sample during the laser light irradiation. The results suggested that the alternative spray technique is the best choose to control of roughness of the films by using light irradiation.

Patterned glass ceramic design for high-brightness high-color-quality laser-driven lightings

Up-to-date laser-driven lightings confront a challenge of simultaneously achieving good photometric and chromatic performances.Herein,the coupling of“patterned package design”and“phosphor wheel”was proposed and demonstrated effectively to deal with this tough issue,based on a new architecture of CaAlSiN3:Eu2+(CASN:Eu)glass ceramic film(GCF)on Y_(3)Al_(5)O_(12):Ce^(3+)(YAG:Ce)GC plate.The fabricated composite has no interface between the two functional layers and retains the admirable luminescent features from CASN:Eu and YAG:Ce for the microstructural integrity during co-sintering.The studies on laser-microcrystalline interactions reveal that the luminescence saturation is almost determined by thermal quenching for YAG:Ce,but is ascribed to thermal/intensity quenching which are equally crucial for CASN:Eu.Benefiting from the elaborate architecture design,good color chromaticity tunability was obtained,and severe photon reabsorption was reduced.Moreover,accompanied with the rotation induced increase of thermal convection to air and pulse-like excitation,the constructed lighting engine under blue laser driven shows bright white light with luminous flux(LF)higher than 1000 lm,adjustable chromaticity from cool to warm,and improved color rendering index(CRI)approaching to 70.

Composition and luminescence properties of highly robust green-emitting LuAG:Ce/Al_(2)O_(3)composite phosphor ceramics for high-power solid-state lighting

The major advantage of laser lighting over white light-emitting-diode is the possibility to achieve ultra-high luminance.However,phosphors usually suffer laser-induced luminescence saturation,which limits the peak luminance of laser lighting devices.The aim of the present study is to develop LuAG:Ce/Al_(2)O_(3)composite ceramics(LACCs)with a high saturation threshold for high-luminance laser lighting.Owning to the rigid crystal structure,proper synthetic process,and optimized thermal design,the LACCs possess small thermal quenching(16%loss in luminescence at 225℃),high quantum yield(>95%),and excellent luminescence properties.When the LACCs are irradiated by blue laser diodes in a reflection mode,a high luminous flux of 4634 lm and luminous efficacy of 283 lm·W^(−1)are realized.Furthermore,they show no sign of luminescence saturation even when the power density reaches 20.5 W·mm^(−2).With these favorable properties,the designed LACCs show great potential in high-luminance laser lighting.

Study on Molecular Chain Morphology of Konjac Glucomannan

The long-range structure of konjac glucomannan(KGM)is studied by using laser light scatter(LLS), gel permeation chromatography(GPC)and method of viscosidity. The weight-average molecular weight(Mw), root-mean-square ratio of gyration[(S2)1/2], second viral coefficient(A2)and multi-dispersion coefficient(Mw/Mn)are 1.04×106, 105. 0±0. 9 nm,(-1. 59±0.28)×10-3 mol ml g-2 and 1.015±0.003, respectively. Mark-Houwink equation is established as [η] = 5. 96×10-2Mw0.73 and the molecular chain parameters are as follows: ML=982. 82 nm-1, Lp = 27. 93 nm, d = 0. 74 nm, h = 0. 26 nm, L = l 054.11 nm. Further more molecular chain morphology of KGM is studied by using atom force microscope(AFM)and transmission electronic microscope(TEM), and the result shows that the KGM molecular is an extending semi-flexible linear chain without branch. Therefore, the image of molecular chain morphology confirms the deduction drawn by Mark-Houwink equation and molecular chain parameters.

VISUALIZATION OF FLOW STRUCTURES IN A TURBULENT BOUNDARY LAYER USING A NEW TECHNIQUE

In this paper, an experimental investigation on the flow structures in a turbulent bounda- ry layer employing a special laser light sheet-Hydrogen bubble flow visualization technique is described. It is observed that the high/low speed streaks are directly related to the hairpin or horseshoe-like vortices. This observation can give a better understanding of the physical mechanism in the turbulent boundary layer.

Tuning the velocity and flux of a low-velocity intense source of cold atomic beam

We investigate experimentally and numerically the quantitative dependence of characteristics of a low-velocity intensity source（LVIS） of atomic beam on light parameters, especially the polarization of cooling laser along the atomic beam axis（pushing beam）. By changing the polarization of the pushing beam, the longitudinal mean velocity of a rubidium atomic beam can be tuned continuously from 10 to 20 m/s and the flux can range from 3 × 10^-8 to 1 × 10^-9 atoms/s, corresponding to the maximum sensitivity of the velocity with respect to the polarization angle of 20（m/s）/rad and the mean sensitivity of flux of 1.2 × 10^-9（atoms/s）/rad. The mechanism is explained with a Monte-Carlo based numerical simulation method, which shows a qualitative agreement with the experimental result. This is also a demonstration of a method enabling the fast and continuous modulation of a low-velocity intense source of cold atomic beam on the velocity or flux,which can be used in many fields, like the development of a cold atomic beam interferometer and atom lithography.

A SLOW RELAXATION MODE OF POLYMER CHAINS IN A SEMIDILUTE SOLUTION

Dust-free semidilute and concentrated polystyrene(PS)solutions in different solvents were prepared by slow evaporation and in situ anionic polymerization,which removes the effects of troublesome artifacts such as dust contamination and concentration gradient.The dynamics was reexamined by a combination of static and dynamic laser light scattering.In benzene and toluene(good solvents for PS),only one fast diffusive mode of polymer chains can be observed when the concentration(c)is up to 20%,which is attribut...

LIGHT-SCATTERING STUDY OF POLYELECTROLYTE HOLLOW CAPSULES

Silver halide (AgX) microcrystal was used as template to synthesize hollow polyelectrolyte capsules. These hollow capsules were characterized by laser light scattering (LLS) used to measure the size of the capsules in solution. The ratio of hydrodynamic radius (R h ) from dynamic LLS to the radius of gyration (Rg) from static LLS is almost unity, revealing that the entities are hollow in solution. The results suggest that the LLS method can be regarded as a good complement to the confocal laser scanning microscopy (CLSM) method for the characterization of small hollow capsules, and it possesses the advantage of not needing fluorescence labeling.

The Case Report on the Effectiveness of Infrared Light on Acid Burn Victim

Burn injuries are common in Pakistan. However, most people are reluctant to have infrared treatment for their wounds. This study investigated the efficacy of infrared treatment on burn wounds. The procedure involved a burn victim who had sustained acid burns to the neck and face. Nectrotomy was done to remove dead tissue from the burn wound, and after treatment, Low-Level Light was used to reduce pain and enhance healing in the patient. Initial results showed mild hypertrophic scars, no stiffness. Post-operation therapy included physical training regimens and massage. The patient showed satisfactory results and felt less tightness in neck movements by the following treatment. The article concludes by showing that infrared light promoted repair and regrowth at a cellular level.

Simultaneous generation of controllable double white light lasers by focusing an intense femtosecond laser pulse in air

We report on a simultaneous generation of double white light lasers through filamentation by focusing a femtosecond laser pulse. The appearance of the two white light lasers can be controlled by tilting the focusing lens. The spectral bandwidth and the pulse energy of the double white light lasers were controlled by tuning laser filamenting pulse energy and polarization. Two white light lasers with pulse energies of 1.54 m J and 1.84 m J,respectively, were generated with the pump laser energy of 7.43 m J. Besides being beneficial in understanding the multiple white light lasers generation process through multiple filamentation and its control, the results are also valuable for white light laser-based applications.

On-chip classification of micro-particles using laser light scattering and machine learning

The rapid detection of microparticles exhibits a broad range of applications in the field of science and technology. The proposed method differentiates and identifies the 2 μm and 5 μm sized particles using a laser light scattering. The detection method is based on measuring forward light scattering from the particles and then classifying the acquired data using support vector machines. The device is composed of a microfluidic chip linked with photosensors and a laser device using optical fiber. Connecting the photosensors and laser device using optical fibers makes the device more diminutive in size and portable. The prepared sample containing microspheres was passed through the channel, and the surrounding photosensors measured the scattered light. The time-domain features were evaluated from the acquired scattered light, and then the SVM classifier was trained to distinguish the particle’s data. The real-time detection of the particles was performed with an overall classification accuracy of 96.06%. The optimum conditions were evaluated to detect the particles with a minimum concentration of 0.2 μg/m L. The developed system is anticipated to be helpful in developing rapid testing devices for detecting pathogens ranging between 2 μm to 10 μm.

Effect of Q-switched Alexandrite laser irradiation on epidermal melanocytes in treatment of Nevus of Ota

To investigate injury to epidermal melanocyte by Q-switched Alexandrite laser Methods Multiple biopsies were performed on 5 patients with nevus of Ota from before irradiation to 1 year after irradiation Fourteen specimens were obtained for light microscopy, and 17 for transmission electron microscopy Results Melanosomes in epidermal melanocytes were both smaller in size and fewer in number than those in dermal melanocytes Immediately after irradiation, focal extracellular vacuoles of the basal layer could be observed under light microscopy Most epidermal melanocytes underwent mild or moderate injury in the form of vacuolated melanosomes, swollen mitochondria, dilation of endoplasmic reticulum, and expansion of extracellular space, retaining intact cell membranes Normal structures were restored 5 months to 1 year after irradiation, with no depigmentation or hyperpigmentation as seen by light microscopy Conclusion Injury of melanosomes in epidermal melanocytes is reversible

Light gain amplification in microcavity organic semiconductor laser diodes under electrical pumping

Organic semiconductor is one of the most promising luminescent and lasing materials that can be chemically synthesized with a controllable performance and possess high cross-section of stimulated emission[1].Organic semiconductor laser diodes(OSLDs)can be prepared by simple processing technologies and integrated easily with other optoelectronic devices.As a result,OSLDs would

SOA Direct Modulation in Wavelength-Selectable Laser Array Light Sources

We demonstrated, for the first time, 2.5-Gb/s SOA direct modulation in the wavelength-selectable DFB laser array. The SOA direct modulation was achieved in the wide tuning range of 22.7nm by selecting arrayed laser and tuning the temperature. 40-km transmission was also confirmed..