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https://www.readbyqxmd.com/read/28508042/toward-continuous-wave-operation-of-organic-semiconductor-lasers
#1
Atula S D Sandanayaka, Toshinori Matsushima, Fatima Bencheikh, Kou Yoshida, Munetomo Inoue, Takashi Fujihara, Kenichi Goushi, Jean-Charles Ribierre, Chihaya Adachi
The demonstration of continuous-wave lasing from organic semiconductor films is highly desirable for practical applications in the areas of spectroscopy, data communication, and sensing, but it still remains a challenging objective. We report low-threshold surface-emitting organic distributed feedback lasers operating in the quasi-continuous-wave regime at 80 MHz as well as under long-pulse photoexcitation of 30 ms. This outstanding performance was achieved using an organic semiconductor thin film with high optical gain, high photoluminescence quantum yield, and no triplet absorption losses at the lasing wavelength combined with a mixed-order distributed feedback grating to achieve a low lasing threshold...
April 2017: Science Advances
https://www.readbyqxmd.com/read/28492049/a-review-of-laser-and-light-therapy-in-melasma
#2
REVIEW
M K Trivedi, F C Yang, B K Cho
Melasma is a dysregulation of the homeostatic mechanisms that control skin pigmentation and excess pigment is produced. Traditional treatment approaches with topical medications and chemical peels are commonly used but due to the refractory and recurrent nature of melasma, patients often seek alternative treatment strategies such as laser and light therapy. Several types of laser and light therapy have been studied in the treatment of melasma. Intense pulsed light, low fluence Q-switched lasers, and non-ablative fractionated lasers are the most common lasers and light treatments that are currently performed...
March 2017: International Journal of Women's Dermatology
https://www.readbyqxmd.com/read/28485872/new-lasers-and-light-sources-old-and-new-risks
#3
REVIEW
Uwe Paasch, Antje Schwandt, Nikolaus Seeber, Gerd Kautz, Sonja Grunewald, Merete Haedersdal
Recent developments (new wavelengths, treatment concepts, and combinations) in the field of lasers, intense pulsed light (IPL), LED, as well as new energy and light sources have opened up new therapeutic options that extend beyond mere aesthetic indications. Thus, while fractional lasers used to be employed to merely treat wrinkles, the same devices - in the context of laser-assisted drug delivery - have now become important tools in the treatment of scars, field cancerization, and epithelial tumors. The requirements posed to physicians, both with respect to establishing the indication and conducting treatment, have been growing along with the increase in technological complexity as well as the rising number of comorbidities and comedications in a patient population that continues to age...
May 2017: Journal der Deutschen Dermatologischen Gesellschaft, Journal of the German Society of Dermatology: JDDG
https://www.readbyqxmd.com/read/28474903/reduction-of-intrinsic-electron-emittance-from-photocathodes-using-ordered-crystalline-surfaces
#4
Siddharth Karkare, Jun Feng, Xumin Chen, Weishi Wan, F Javier Palomares, T-C Chiang, Howard A Padmore
The generation of intense electron beams with low emittance is key to both the production of coherent x rays from free electron lasers, and electron pulses with large transverse coherence length used in ultrafast electron diffraction. These beams are generated today by photoemission from disordered polycrystalline surfaces. We show that the use of single crystal surfaces with appropriate electronic structures allows us to effectively utilize the physics of photoemission to generate highly directed electron emission, thus reducing the emittance of the electron beam being generated...
April 21, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28463283/high-resolution-flash-three-dimensional-lidar-systems-based-on-polarization-modulation
#5
Peng Zhang, Xiaoping Du, Jiguang Zhao, Yishuo Song, Hang Chen
Two high resolution flash LIDAR systems based on polarization modulation are demonstrated in this paper. One utilizes a polarization beam splitter (PBS) and two charge coupled device (CCD) arrays; the other utilizes a micro-polarizer array and a CCD array. Compared with the traditional flash LIDAR systems, the main advantage of the presented flash LIDAR systems is replacing high bandwidth detectors with a polarization modulator and low bandwidth detectors. The polarization modulator is used to modulate the polarization state of the received laser pulse in time and the range information can be mapped into the intensity received by the low bandwidth detectors...
May 1, 2017: Applied Optics
https://www.readbyqxmd.com/read/28456263/note-energy-calibration-of-a-femtosecond-photoelectron-imaging-detector-with-correction-for-the-ponderomotive-shift-of-atomic-ionization-energies
#6
O Hüter, F Temps
Femtosecond photoelectron imaging spectroscopy is a powerful technique for following state-resolved molecular transformations in complex coupled potential energy landscapes. To avoid unwanted nonlinear side-effects, the employed laser pulse energies are usually reduced to minimal values. However, the energy calibration of the photoelectron imaging detector is ideally performed using multi-photon above-threshold ionization of suitable atomic species, for which rather high laser intensities are required. In this work, we show that the calibration spectra of xenon obtained with high laser pulse energies cannot be directly used for the evaluation of molecular photoelectron spectra recorded using low-energy laser pulses...
April 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/28438002/hot-luminescence-from-gold-nanoflowers-and-its-application-in-high-density-optical-data-storage
#7
Yunbao Zheng, Haiying Liu, Jin Xiang, Qiaofeng Dai, Min Ouyang, Shaolong Tie, Sheng Lan
Gold nanoflowers with feature sizes ranging from several tenths to several hundred nanometers were synthesized by using the one-pot method. They were formed by the self-organization of gold nanoparticles of several nanometers and exhibited broad extinction spectra in the near infrared spectral range. Randomly distributed hot spots originating from the strongly localized modes were generated in gold nanoflowers and their appearances exhibited strong dependences on both the polarization and wavelength of the excitation light...
April 17, 2017: Optics Express
https://www.readbyqxmd.com/read/28428549/low-noise-time-resolved-optical-sensing-of-electromagnetic-pulses-from-petawatt-laser-matter-interactions
#8
T S Robinson, F Consoli, S Giltrap, S J Eardley, G S Hicks, E J Ditter, O Ettlinger, N H Stuart, M Notley, R De Angelis, Z Najmudin, R A Smith
We report on the development and deployment of an optical diagnostic for single-shot measurement of the electric-field components of electromagnetic pulses from high-intensity laser-matter interactions in a high-noise environment. The electro-optic Pockels effect in KDP crystals was used to measure transient electric fields using a geometry easily modifiable for magnetic field detection via Faraday rotation. Using dielectric sensors and an optical fibre-based readout ensures minimal field perturbations compared to conductive probes and greatly limits unwanted electrical pickup between probe and recording system...
April 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28427634/enhanced-porosity-and-permeability-of-three-dimensional-alginate-scaffolds-via-acoustic-microstreaming-induced-by-low-intensity-pulsed-ultrasound
#9
Gepu Guo, Yong Ma, Yang Guo, Chunbing Zhang, Xiasheng Guo, Juan Tu, Alfred C H Yu, Junru Wu, Dong Zhang
The shear stress resulting from the microstreaming induced by low-intensity pulsed ultrasound (LIPUS) has been often used to improve the permeability of cell membrane or porous engineering scaffolds. In the present study, three-dimensional (3-D) scaffold culture systems were constituted to simulate the in vivo microenvironment, providing benefits for cell growth. In order to investigate the mechanism underlying the enhanced porosity and permeability of the 3-D alginate scaffolds by using LIPUS with varied acoustic intensities, two quantitative imaging techniques (i...
July 2017: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/28414231/organic-phosphorescence-nanowire-lasers
#10
Zhenyi Yu, Yishi Wu, Lu Xiao, Jianwei Chen, Qing Liao, Jiannian Yao, Hongbing Fu
Organic solid-state lasers (OSSLs) based on singlet fluorescence have merited intensive study as an important class of light sources. Although the use of triplet phosphors has led to 100% internal quantum efficiency in organic light-emitting diodes (OLEDs), stumbling blocks in triplet lasing include generally forbidden intersystem crossing (ISC) and a low quantum yield of phosphorescence (ΦP). Here, we reported the first triplet-phosphorescence OSSL from a nanowire microcavity of a sulfide-substituted difluoroboron compound...
April 25, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28383017/room-temperature-subnanosecond-waveguide-lasers-in-nd-yvo4-q-switched-by-phase-change-vo2-a-comparison-with-2d-materials
#11
Weijie Nie, Rang Li, Chen Cheng, Yanxue Chen, Qingming Lu, Carolina Romero, Javier R Vázquez de Aldana, Xiaotao Hao, Feng Chen
We report on room-temperature subnanosecond waveguide laser operation at 1064 nm in a Nd:YVO4 crystal waveguide through Q-switching of phase-change nanomaterial vanadium dioxide (VO2). The unique feature of VO2 nanomaterial from the insulating to metallic phases offers low-saturation-intensity nonlinear absorptions of light for subnanosecond pulse generation. The low-loss waveguide is fabricated by using the femtosecond laser writing with depressed cladding geometry. Under optical pump at 808 nm, efficient pulsed laser has been achieved in the Nd:YVO4 waveguide, reaching minimum pulse duration of 690 ps and maximum output average power of 66...
April 6, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28382317/probing-ultra-fast-processes-with-high-dynamic-range-at-4th-generation-light-sources-arrival-time-and-intensity-binning-at-unprecedented-repetition-rates
#12
S Kovalev, B Green, T Golz, S Maehrlein, N Stojanovic, A S Fisher, T Kampfrath, M Gensch
Understanding dynamics on ultrafast timescales enables unique and new insights into important processes in the materials and life sciences. In this respect, the fundamental pump-probe approach based on ultra-short photon pulses aims at the creation of stroboscopic movies. Performing such experiments at one of the many recently established accelerator-based 4th-generation light sources such as free-electron lasers or superradiant THz sources allows an enormous widening of the accessible parameter space for the excitation and/or probing light pulses...
March 2017: Structural Dynamics (Melville, N.Y.)
https://www.readbyqxmd.com/read/28338214/light-therapies-for-acne-abridged-cochrane-systematic-review-including-grade-assessments
#13
REVIEW
J Barbaric, R Abbott, P Posadzki, M Car, L H Gunn, A M Layton, A Majeed, J Car
We undertook a Cochrane review of randomized controlled trials (RCTs) evaluating the effects of light-based interventions for acne vulgaris. We searched the Cochrane Skin Specialised Register, CENTRAL, MEDLINE, Embase, LILACS, ISI Web of Science, and grey literature sources (September 2015). We used the Grading of Recommendations Assessment, Development and Evaluation Working Group approach to assess the quality of evidence (QE). We included 71 RCTs (4211 participants, median sample size 31). Results from a single study (n = 266, low QE) showed little or no difference in effectiveness on participants' assessment of improvement between 20% aminolevulinic acid (ALA) photodynamic therapy (PDT), activated by blue light, versus vehicle plus blue light, whereas another study (n = 180) of a comparison of ALA-PDT (red light) concentrations showed 20% ALA-PDT was no more effective than 15%, but better than 10% and 5% ALA-PDT...
March 24, 2017: British Journal of Dermatology
https://www.readbyqxmd.com/read/28317370/two-dimensional-ch3nh3pbi3-perovskite-nanosheets-for-ultrafast-pulsed-fiber-lasers
#14
Pengfei Li, Yao Chen, Tieshan Yang, Ziyu Wang, Han Lin, Yanhua Xu, Lei Li, Haoran Mu, Bannur Nanjunda Shivananju, Yupeng Zhang, Qinglin Zhang, Anlian Pan, Shaojuan Li, Dingyuan Tang, Baohua Jia, Han Zhang, Qiaoliang Bao
Even though the nonlinear optical effects of solution processed organic-inorganic perovskite films have been studied, the nonlinear optical properties in two-dimensional (2D) perovskites, especially their applications for ultrafast photonics, are largely unexplored. In comparison to bulk perovskite films, 2D perovskite nanosheets with small thicknesses of a few unit cells are more suitable for investigating the intrinsic nonlinear optical properties because bulk recombination of photocarriers and the nonlinear scattering are relatively small...
March 29, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28315815/self-assembled-photoadditives-in-polyester-films-allow-stop-and-go-chemical-release
#15
Ting Cheng, Richard O'Rorke, Raphael Francois Ortiz, Tay Yee Yan, Eva Hemmer, Fiorenzo Vetrone, Robert S Marks, Terry W J Steele
Near-infrared (NIR) triggered chemical delivery allows on-demand release with the advantage of external tissue stimulation. Bioresorbable polyester poly-l-lactic acid (PLLA) was compounded with photoadditives of neat zinc oxide (ZnO) nanoparticles and 980→365nm LiYF4:Tm(3+), Yb(3+) upconverting nanoparticles (UCNP). Subsequently, neat ZnO and UCNP blended PLLA films of sub-50μm thickness were knife casted with a hydrophobic small molecule drug mimic, fluorescein diacetate. The PLLA films displayed a 500 times increase in fluorescein diacetate release from the 50mW NIR irradiated PLLA/photoadditive film compared to non-irradiated PLLA control films...
March 16, 2017: Acta Biomaterialia
https://www.readbyqxmd.com/read/28288450/laser-treatment-of-tattoos-basic-principles
#16
Wolfgang Bäumler
Tattooing has become very popular worldwide during the past decades, and millions of people have one or many tattoos at different anatomical sites. The color of tattoos is mainly black, followed by red, green, blue, and other colors. A part of the tattooed people regret tattooing or have permanent problems with tattoos and therefore seek for tattoo removal. Tattoos consist of solid pigment particles in the skin. Thus, tattoo removal requires fragmentation of these permanently incorporated particles. The gold standard of tattoo removal is laser therapy...
2017: Current Problems in Dermatology
https://www.readbyqxmd.com/read/28279642/low-intensity-400%C3%A2-mw-cm-2-500%C3%A2-khz-pulsed-transcranial-ultrasound-preconditioning-may-mitigate-focal-cerebral-ischemia-in-rats
#17
Hangdao Li, Junfeng Sun, Daqu Zhang, Daryl Omire-Mayor, Peter A Lewin, Shanbao Tong
BACKGROUND: Preconditioning methods, which could increase tolerance of brain to subsequent ischemic injuries with a small dose of non-injury stimuli, have gained attention. Capitalizing on noninvasiveness and safety of ultrasound modality, the pulsed transcranial ultrasound stimulation (pTUS) approach may provide a novel treatment for patients with high risk of stroke. OBJECTIVE: This study's goal was to investigate whether the risk of stroke could be minimized or eliminated by prior exposure to low-intensity, pulsed transcranial ultrasound stimulation (pTUS)...
May 2017: Brain Stimulation
https://www.readbyqxmd.com/read/28271006/vcsel-based-swept-source-for-low-cost-optical-coherence-tomography
#18
Sucbei Moon, Eun Seo Choi
We present a novel wavelength-swept laser source for optical coherence tomography (OCT) which is based on the conventional laser diode technology of the vertical-cavity surface-emitting laser (VCSEL). In our self-heating sweep VCSEL (SS-VCSEL), a VCSEL device is simply driven by ramped pulses of currents in direct intensity modulation. The intrinsic property of VCSEL produces a frequency-swept output through the self-heating effect. By the injected current, the temperature of the active region is gradually increased in this effect...
February 1, 2017: Biomedical Optics Express
https://www.readbyqxmd.com/read/28267751/cost-effectiveness-of-adjunct-non-pharmacological-interventions-for-osteoarthritis-of-the-knee
#19
Beth Woods, Andrea Manca, Helen Weatherly, Pedro Saramago, Eleftherios Sideris, Christina Giannopoulou, Stephen Rice, Mark Corbett, Andrew Vickers, Matthew Bowes, Hugh MacPherson, Mark Sculpher
BACKGROUND: There is limited information on the costs and benefits of alternative adjunct non-pharmacological treatments for knee osteoarthritis and little guidance on which should be prioritised for commissioning within the NHS. This study estimates the costs and benefits of acupuncture, braces, heat treatment, insoles, interferential therapy, laser/light therapy, manual therapy, neuromuscular electrical stimulation, pulsed electrical stimulation, pulsed electromagnetic fields, static magnets and transcutaneous electrical nerve Stimulation (TENS), based on all relevant data, to facilitate a more complete assessment of value...
2017: PloS One
https://www.readbyqxmd.com/read/28256507/high-operating-temperature-and-low-power-consumption-boron-nitride-nanosheets-based-broadband-uv-photodetector
#20
Manuel Rivera, Rafael Velázquez, Ali Aldalbahi, Andrew F Zhou, Peter Feng
We extend our work on the use of digitally controlled pulsed laser plasma deposition (PLPD) technique to synthesize high quality, 2-dimensional single crystalline boron nitride nanosheets (BNNSs) at a low substrate temperature for applications in high-performance deep UV photodetectors. The obtained sample consists of a large amount of BNNSs partially overlapping one another with random orientations. Each sheet is composed of a few (from 2 to 10) stacked atomic layers exhibiting high transparency due to its highly ordered hBN crystallinity...
March 3, 2017: Scientific Reports
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