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Presents information on a study which demonstrated the potential for laser operation at far-infrared wavelengths by using intersubband emission in four level gallium (Ga) arsenic (As)/aluminum (Al)GaAs asymmetric quantum wells. Methodology of the study; Results and discussion on the study; Conclusions.

Cemented carbide (YG8) is commonly applied to workplaces where friction and wear are severe. Therefore, improving the surface friction performance is of great significance. Surface micro-texture technology is exactly a feasible method. However, due to high wear resistance and hardness of YG8, it is difficult to process surface texture with accurate feature size by traditional methods. In this paper, four types of groove-shaped textures were etched on the surface of YG8 discs by high peak power UV nanosecond laser. The error of texture width could be controlled within ±5 μm. Friction and wear tests were performed using a standard ball-on-disc configuration to investigate the influence of the texture parameters (width and area ratio of grooved textures) on the friction-reducing and wear-resistance properties under constant load and relative sliding speed. Antifriction mechanism of textures was analyzed and a theoretical model of texture under dry friction condition was presented. As shown in the experimental results, the optimal texture parameters have a good gain effect on friction-reducing and wear-resistance of cemented carbide surface under dry friction and solid lubrication. Friction coefficient was reduced from 0.301 to 0.275 and 0.138, respectively. The theoretical model has good agreement with the experimental data and could provide theoretical support for predicting the optimal parameters of texture. • High-precision and well-formed textures were prepared on the cemented carbide surface by high UV nanosecond laser. • The radially arranged groove texture allowed the texture area ratio to be distributed from 10% to 50%. • The effect of texture parameters on the friction coefficient was studied. • The friction reduction mechanism of texture was studied and the friction coefficient prediction model was obtained. [ABSTRACT FROM AUTHOR]

In this paper, the different spot phenomena of high-order laser cavity under wire interference diffraction are verified experimentally. Firstly, we customize an external cavity He-Ne laser tube which can directly generate high-order Gaussian beams with various modes, good beam stability and outstanding quality. This device is easy to operate and easy to implement. We have done some research on this laser cavity. On this basis, we use a wire with a diameter of 0.15 mm to deform and then interfere with the beam, and use a CMOS camera to collect the diffraction pattern of the beam. Finally, the induction and summary of the experimental phenomena under different steel wires are carried out, and the change process of high-order Gaussian beams is recorded in detail, which provides an experimental precedent for future research. [ABSTRACT FROM AUTHOR]

In this paper, a laser interference lithography technology which based on the mutual injection dual-output laser is innovatively developed. The experimental study of two beams of laser interference lithography on the material surface is carried out by using two beams of phase locking and the same frequency output. In order to solve the problems caused by beam splitter in laser interference lithography in the past, such as unequal energy, high loss and unsatisfactory interference pattern. U cavity structure is constructed by using two pump gain dielectric devices and two perpendicular 45° total reflection mirrors in the experiment. Outputing two parallel beams with pulse width of 8.2 ns and energy of 186 mJ after intracavity electro-optic Q-switching. Then using two other reflection mirrors to make the two beams of light reflection convergence onto the surface of the silicon material for interference lithography. When the angles of two beams are 12°, 9°and 6°, the clear interference fringes with periods of 5.1 μm, 6.9 μm and 10.4 μm are obtained. The interference photolithography using a dual-output laser with mutual injection has a positive significance for micromachining technology, and it can be extended to multi-channel laser interferometry processing using multi-channel mutual injection lasers. [ABSTRACT FROM AUTHOR]

Aiming at the phenomenon of plasma acoustic wave during laser shock processing, the online monitoring method of laser shock processing based on plasma acoustic wave signal energy is proposed. The TC4 titanium alloy samples, after the vibration stress relief treatment, were treated by a Nd:YAG laser system with a wavelength of 1064nm, a pulse width of 12–18 ns, and a single pulse energy of 0–7 J. The plasma acoustic wave in air is sampled, stored, digitally filtered, and analyzed by the laser shock processing online monitoring system during laser shock processing. Then the system gets the plasma acoustic wave signal energy. The surface residual stress of material after the treatment of laser shock processing were measured by a Photo-LXRD X-ray diffraction device. The experimental results show that the residual compressive stress is generated on the surface of material after laser shock processing. Both the surface residual stress of the material and the plasma acoustic wave signal energy are increased as the laser pulse energy increases from 3J to 7J, and their growth trend is consistent. Finally, the empirical formula between the surface residual compressive stress of the material and the plasma acoustic wave signal energy is obtained by polynomial fitting, which will provides a theoretical basis for the development of laser shock processing online monitoring technology. [ABSTRACT FROM AUTHOR]

Experiments to enhance photoneutron production from the Ta (γ,xn) reaction with 100 TW picosecond laser pulses irradiating on gas-solid hybrid targets have been performed on the XingGuangIII laser facility at the Laser Fusion Research Center (LFRC) in Mianyang. The so-called gas-solid hybrid target was composed of a 1 mm thick N2 gas jet and a 2 cm thick Ta block. Picosecond laser pulses with intensities up to 1019 W/cm2 first interact with the tenuous gas to enhance the yields of high energy electrons through the direct laser acceleration (DLA) mechanism, and then through bremsstrahlung and subsequent (γ, n) reactions in a Ta converter, photoneutrons were enhanced effectively and the total number of neutrons was optimized by changing the gas density. A maximum neutron yield of 4 × 107/shot over 4π was achieved which is 200 times higher than that in the direct laser-solid interaction shot in our experiment. The spectrum of photoneutrons was measured which is in agreement with Monte Carlo (MC) simulation. From the size of the reaction area and the neutron pulse duration inferred from simulation, the corresponding flux was calculated to be 1.2 × 1016 n/cm2/s. [ABSTRACT FROM AUTHOR]

Elucidation of the mechanisms of laser damage is indispensable in realizing high resistance mirrors for the next generation of ultra-short pulse high intensity lasers. In this study, the surface and a section of the laser-damaged area of a laser mirror were observed with a laser microscope and a transmission electron microscope (cross-sectional TEM), respectively. A grain boundary of HfO2 microcrystal was observed in the damaged area. This observation and an evaluation of the mirror's damage resistance showed that the formation of crystals in the multilayer mirror is one of the major determinants of damage resistance. [ABSTRACT FROM AUTHOR]

The fundamental issues associated with the magnetoplasmon excitations are investigated in a quantum wire characterized by a confining harmonic potential and subjected to a perpendicular magnetic field. Essentially, we embark on the device aspects of the intersubband collective (magnetoroton) excitation which observes a negative group velocity between the maxon and the roton. The computation of the gain coefficient suggests an interesting and important application: the electronic device based on such magnetoroton modes can act as an active laser medium. [ABSTRACT FROM AUTHOR]

In conventional two-dimensional (2-D) ghost imaging (GI), intensity images can be obtained by utilizing the intensity correlation between signals in the reference path and test path. Grey values in ghost imaging represent the transmission coefficient or reflection coefficient of the target. In this study, colour fusion polarization ghost imaging (CPGI) system is proposed to acquire polarization image of target through Stokes parameters. A polarized chromatic value (PCV) is introduced in this system to describe Stokes parameters in a pseudo-colour way. Target information can easily be extracted from the result of CPGI system. The proposed method can be employed successfully to identify targets, promoting wider application of ghost imaging systems. [ABSTRACT FROM AUTHOR]

A special phenomenon about laser spot tail in dual channel type linear CCD is studied. In the CCD, the charges packets in odd and even number pixels are respectively transferred by two channels, in which, the threshold difference of surface full well induces the length difference of spot tails. So, the terminal vibration of spot tail is caused. A simulation of this phenomenon is given and qualitatively validated by the experiment results of laser irradiating a dual channel type linear CCD. In the experiment, the phenomenon has been used to estimate relative size of surface full well thresholds in two channels of CCD. [ABSTRACT FROM AUTHOR]

A laser range-gated viewing experiment in the eye-safe spectral region is demonstrated where a semiconductor based laser illuminator is associated with a corresponding image detector able to operate in high frequency and high sensitivity shutter mode. After experimental validations of the camera developed for accumulation operation, a high power semiconductor based illuminator has been designed and realized. This technology can be used to develop efficient, compact and high average power SWIR illuminators. Images of different scenes were recorded in a test tunnel and the results are compared to those recorded simultaneously with a solid state based laser illuminator working in flash mode. Both results are similar in terms of image intensity whereas semiconductor based recordings exhibits lower speckle noise and better homogeneity. These results open new opportunities for compact and efficient SWIR active imaging systems. [ABSTRACT FROM AUTHOR]

By power scaling of LEDs pump concentrators we demonstrated a visible light source (centered at 550 nm) producing 294 W with a radiance of 668 W/cm 2 /sr in the air. Using more than 1100 LEDs, this setup represents one order of magnitude improvement in terms of output power and brightest of LED pump concentrator ever reported. We pushed further the concept of low cost high brightness light source using this concentrator to pump a very simple Nd:YAG laser in free running mode and in passively Q-switched regime using a Cr:YAG saturable absorber. Output energies up to 263 µJ with a pulse duration of 33 ns have been obtained at 1064 nm, leading to a peak power of 8 kW in a TEM 00 mode. [ABSTRACT FROM AUTHOR]

This study aimed to explore the electrochemical properties and microstructure of friction stir welds to understand the correlation between their properties and processing. Friction stir welding is a promising solid-state joining process for high-strength aluminum alloys (AA). Although friction stir welding (FSW) eliminates the problems of fusion welding due to the fact that it is performed below T m , it causes severe plastic deformation in the material. Some AA welded by FSW exhibit relatively poor corrosion resistance. In this research, the corrosion resistance of such welds was enhanced through laser surface melting. A friction stir weld of AA 2219 was laser melted. The melt depth and microstructure were observed using optical and scanning electron microscopy. The melt zone exhibited epitaxially grown columnar grains. The redistribution of elemental composition was analyzed using energy-dispersive spectroscopy. The anticorrosion properties of both laser-melted and original welds were studied in aqueous 3.5% NaCl solution using cyclic potentiodynamic polarization. The results indicated a noticeable increase in the pitting corrosion resistance after the laser treatment on the surface. The repassivation potential was nobler than the corrosion potential after the laser treatment, confirming that the resistance to pitting growth improved. [ABSTRACT FROM AUTHOR]

We fabricate a capsule-shaped metal-clad wavelength-scale InP/InGaAs cavity and demonstrate room-temperature lasing at a wavelength of ~1550 nm under pulsed optical pumping. By introducing an optimized curvature to the sidewalls of a conventional rectangular metal-clad laser, we effectively reduce the metallic loss of the transverse-electric mode and experimentally confirm a clear improvement in the side mode suppression ratio and slope efficiency. [ABSTRACT FROM AUTHOR]

In this paper a doubly Q-switched 1.06 μm Nd:YVO4 pulse laser with acoustic-optic (AO) Q-switch and Cr4+:YAG saturable absorber passive Q-switch was demonstrated. The pulse width was compressed from 22.6 to 17.5 ns and the pulse peak power was increased from 3.92 to 4.17 kW for the doubly Q-switched laser when compared with the acoustic-optics Q-switched laser at the conditions of incident pump power of 12 W and repetition rate of 50 kHz. [ABSTRACT FROM AUTHOR]

Distinguishing label-free malignant cells from healthy ones by their laser scattering spectra is still a tough challenge in label-free cells detection methods. During cells malignant transferring, some tiny structural differences occurs. The nucleus, as the most important internal structure, has very close relationships with cell's healthy state. In this paper, cells with similar size but different tiny nucleus differences are set as the research objects. A novel cell's laser scattering processing algorithm, even interval incident angle (EIIA) algorithm, is developed which is effective in distinguish label-free cells with tiny nucleus' size difference. The laser scattering spectra of human acute leukaemia Jurkat cell models with different nuclei are processed by EIIA to test its sensitivity and reliability. The results prove that cell's original tightly compacted laser scattering spectra have been well separated by EIIA. A consistent rule for cell's nucleus becoming larger can be obviously observed in EIIA processed laser scattering results, which is promising to be an effective standard for identifying malignant larger nucleus cells from healthy ones; therefore, a valid pathway for identify label-free cells simply and directly by their laser scattering spectra can be implemented by EIIA. Also, it may supply an important clinic diagnosis tool to detect malignant cells in early cancerous stage without any dying and marking procedures. [ABSTRACT FROM AUTHOR]

In this research contour laser transmission welding (LTW) of thermoplastics is systematically studied through process modelling, finite element method (FEM) and response surface methodology (RSM) combined approach. Effect of process parameters on temperature field and weld bead dimension have been studied. The thermal field simulated by solving a three-dimensional (3-D) transient heat diffusion equation with temperature dependent material properties using the COMSOL multi-physics. MINITAB 16 software has been used for experimental design. RSM is applied for developing mathematical models based on simulation results. The interactions of process parameters on the responses are studied using the developed response surface models. It is found that responses like, weld width, depth of penetration in absorbent part and maximum temperature at weld interface have been decreased with increasing value of scanning speed. According to analysis-of-variance (ANOVA) the laser power and spot diameter is the significant factors on the maximum temperature at weld interface. [ABSTRACT FROM AUTHOR]

The linewidth enhancement (α factor) due to fluctuations in the refractive index induced by carrier fluctuations of intersubband lasers was initially expected to be zero. However, values ranging from −0.5 to 3 have been found experimentally. This paper resolves this controversy showing that counter rotating terms, usually ignored in simulations, are the actual fundamental origin of nonzero α at peak gain even without the inclusion of nonparabolicity and manybody effects, which are however needed to explain negative values. For laser without inversion conditions, significant as a potential out of the box solution for the elusive room temperature operation of terahertz lasers, α is found to be larger, but still at the same order of magnitude of conventional inverted medium lasers, thus ensuring their applicability to a huge number of spectroscopic applications that require sharp laser linewidths. [ABSTRACT FROM AUTHOR]

The present paper is concerned with the analytical and numerical investigation of the transverse spatio-temporal instabilities in two-level broad-area lasers for the specific class-B case. We show that the two-level class-B broad-area laser tends to naturally operate in the filamentary state. This is revealed to be provided with two causes. First of them is related with the homogeneous output profile being intrinsically unstable due to the traveling-wave instability, independently from the boundary conditions. Secondly, high sensitivity to the boundaries of the pumping region was found for the commonly used top-hat-like profile leading to boundaries-induced filamentary dynamics. Spatio-temporal properties of both instability mechanisms are studied and their effects on the resulting laser dynamical behavior are analyzed. [ABSTRACT FROM AUTHOR]

For skin tightening, ablative and nonablative lasers have been used with various parameters full or fractionated. Currently, other energy-based technologies have been developed such as radiofrequency (RF) from mono- to multipolar, microneedling RF, and high-intensity focused ultrasound. They heat up the tissue to a clinical endpoint. Temperatures above 42°C stimulate fibroblasts to produce more collagen and some technologies produce small coagulation points that allow to shrink and to tighten the tissue with less downtime or side effects. Alternative treatments not based on heat can be chemical peels from light to deep and microneedling without RF. [ABSTRACT FROM AUTHOR]

Microscale laser dynamic flexible forming (µLDFF) is a novel micro-forming process. Laser-induced shockwaves act on the soft punch to deform the metal foils. In this article, the forming properties of the µLDFF process are studied from four angles, namely, the maximum deformation depth, accuracy, thickness thinning ratio, and surface quality. The maximum deformation depth of the samples formed under different laser energies was measured. The 2D profiles of the workpieces were measured to study the accuracy. The results show that the deformed samples replicated the mold features well. The cold-mounted technique was used to measure the thickness of the deformed metal foils along the cross section and to discuss the thickness thinning ratio. The results show that µLDFF can reduce localized necking and stress concentrations effectively. The surface roughness was characterized to study the surface quality of the workpieces, and the results indicated that the deterioration of the formed surface was weakened during µLDFF. The advantages of the ultrahigh strain rate and soft punch are both presented in the µLDFF process, which is favorable for fabricating micro components. [ABSTRACT FROM AUTHOR]

The recent increasing research interest in two-dimensional (2D) layered materials has led to an explosion of in the discovery of novel physical and chemical phenomena in these materials. Among the 2D family, group-VI transition metal dichalcogenides (TMDs), such as represented by MoS2 and WSe2, are remarkable semiconductors with sizable energy band gaps, which make the TMDs promising building blocks for new generation optoelectronics. On the other hand, the specificity and tunability of the band gaps can generate particularly strong light–matter interactions between TMD crystals and specific photons, which can trigger complex and interesting phenomena such as photo-scattering, photo-excitation, photo-destruction, photo-physical modification, photochemical reaction and photo-oxidation. Herein, we provide an overview of the phenomena explained by various interactions between lasers and the 2D TMDs. Characterizations of the optical fundamentals of the TMDs via laser spectroscopies are reviewed. Subsequently, photoelectric conversion devices enabled by laser excitation and the functionality extension and performance improvement of the TMDs materials via laser modification are comprehensively summarized. Finally, we conclude the review by discussing the prospects for further development in this research area. [ABSTRACT FROM AUTHOR]

In LBIC systems, the evaluation of the injection level is necessary when operating in low injection for defect recombination studies or in defined standard illumination conditions (one or several suns for concentrator applications) for quantum efficiency evaluation. We demonstrate in this contribution that evaluating the laser beam induced injection based on uniform illumination condition can lead to several decades of error because of the lateral carrier diffusion. Based on a parallel beam approximation, we propose here an analytical model to evaluate the maximum of injection of a laser with its parametrization valid for most LBIC system settings and material quality. State of the art high resolution LBIC (HR-LBIC) systems have so sharply focused laser beams that the beam divergence cannot be neglected anymore in the injection calculation. Although providing a quantitative criterion to determine whether the beam divergence can be neglected, we provide a more advanced model for describing the injection of the laser that includes beam divergence. [ABSTRACT FROM AUTHOR]

We present a rare-earth-doped sapphire laser. Single-crystalline α-Al2O3 films doped with trivalent neodymium have been grown by pulsed laser deposition on undoped sapphire substrates. The Nd3+ doping concentrations of the films have been varied between 0.3 at.% and 2 at.%. Epitaxial growth was proven by structural and optical characterization of the films. The samples exhibit strongly polarization dependent emission transitions from the 4F3/2 manifold with a fluorescence lifetime of 108 μs and peak emission cross sections of 1.1 × 10−18 cm2 around 1100 nm. Lasing at 1096.5 nm was achieved under Ti:sapphire-pumping in a planar waveguide configuration with a maximum cw output power of 137 mW and a slope efficiency of 7.5% with respect to the incident pump power. [ABSTRACT FROM AUTHOR]

A proof-of-concept of space-borne laser filamentation for atmospheric remote sensing is presented. The remote generation of laser filaments from an Earth-orbiting satellite is shown by numerical simulations to be theoretically possible for a large range of laser parameters. The model includes a realistic representation of the stratified atmosphere and accounts for multi-species ionization and the dependence of air density upon the molecule type and altitude profile. The remote generation of a white light continuum extending from 350 nm to 1.1 μm within the filament is demonstrated, and hereby proposed as an atmospheric in-situ light source for monitoring greenhouse gases and pollutants on a global scale by light detection and ranging (lidar) techniques. Scaling laws are also derived for estimating the filament altitude as a function of peak pulse power (3 GW-3 TW), beam radii (10-200 cm) and for three different curvatures (300, 390, 500 km) for femtosecond infrared (800 nm) pulses. We find that operating conditions for remote supercontinuum generation are already available with current ground-based mobile laser technology and within reach of future space laser systems. [ABSTRACT FROM AUTHOR]

Nanoscale lasers are attractive for their potential applications in highly integrated photonic devices and systems. Here, nanolaser arrays are realized based on individual waved CdS nanoribbons (NRs) with periodically modulating thickness along the length direction. Microstructure investigations reveal that such a waved NR is formed with triangular-prism-like ridges alternately assembled on both sides of a surface flat nanoribbon. Under the focused laser (488 nm) excitation, the emitted light is guided along the length of the waved ribbons and can be well confined into theses ridges, being reflected and leaked out at their ends along both the lateral sides of the NRs. Polarization measurements further demonstrate the formation of the cavities along the length of the ridges. Under pulse laser excitation, the confined light in all these parallel ridges can resonate and realize lasing, forming a nanolaser array based on these individual waved NRs. These nanolasers arrays have potential applications in highly integrated photonics, signal processing, and high-throughput sensing. [ABSTRACT FROM AUTHOR]

In flat-type light-emitting-diode (LED) lighting systems, a planar light is formed using a luminance source positioned on the side of the system and light guide panel (LGP) or reflecting plates. Thus, such systems are favorable for their thinness, which allows a relatively small number of LEDs to be used. However, the application of a high-power LED light to a large-area lighting system yields Lambertian luminaires; therefore, a point or a discomfort glare is produced, which generally causes degradation of the luminance efficiency and uniformity. In this study, we solved the problems of luminance non-uniformity and inefficiency by adjusting the orientation of an applied LGP scattered pattern and removing the remaining glare. Through computer simulation, optical characteristics that increase the efficiency even in the case of low-output LEDs were found. Specifically, a scattered pattern vertically oriented relative to the direction of the incident light improves the luminance uniformity at the side of the system, while a scattered pattern oriented parallel to the direction of the incident light plays the role of a waveguide. We implemented a flat-type LED lighting system by fabricating a large-area LGP based on the computer-simulation results and using an extremely sensitive laser. The optical characteristics observed using the laser-processed LGP were identical to those obtained in the computer simulation. Therefore, for large-area flat-type LED lighting systems, we confirmed that adjusting the orientation of the LGP scattered pattern can increase the luminance efficiency and uniformity. [ABSTRACT FROM AUTHOR]

The 3-D particle-in-cell simulations with the code MANDOR demonstrate effective ion acceleration from the interaction of intense ultrashort linearly polarized laser pulses with both ultrathin solid dense foils and low-density targets when the laser energy ranges from several millijoules to tens of joules. The optimum foil thickness and the corresponding maximum energy of the accelerated ions for a given energy of the laser pulse were found. Different mechanisms of ion acceleration, such as target normal sheath acceleration, directed Coulomb explosion, and ponderomotive acceleration, are involved. We discuss the transition from one acceleration regime to another when the target thickness and density and the laser pulse intensity change and show that reducing the target density significantly increases the ion energy. We present some examples of isotope production as a possible application of multimegaelectronvolt proton beams on the joule scale of a laser. [ABSTRACT FROM PUBLISHER]

We have realized GaAs/AlAs quantum-cascade lasers operating at 4.75 THz exhibiting more than three times higher wall plug efficiencies than GaAs/Al0.25Ga0.75As lasers with an almost identical design. At the same time, the threshold current density at 10K is reduced from about 350 A/cm2 for the GaAs/Al0.25Ga0.75As laser to about 120 A/cm2 for the GaAs/AlAs laser. Substituting AlAs for Al0.25Ga0.75As barriers leads to a larger energy separation between the subbands reducing the probability for leakage currents through parasitic states and for reabsorption of the laser light. The higher barriers allow for a shift of the quasi-continuum of states to much higher energies. The use of a binary barrier material may also reduce detrimental effects due to the expected composition fluctuations in ternary alloys. [ABSTRACT FROM AUTHOR]

On account of the large compatibility difference between glass fiber-reinforced Polyamide 66 (GFR-PA66) and Polycarbonate (PC), it is difficult to weld them directly by laser. A new technology is introduced in this article by which the transparent PC is successfully welded with GFR-PA66 using cold spraying in order to spray a 20 lm-thick aluminum film on GFR-PA66 as the absorbed layer. Tensile shear tests show the tensile strength of welded joints is highly enhanced. The influences of bubbles, glass fiber, and aluminum atoms on the performance of the joins are investigated via the optical microscope. X-ray Photoelectron Spectrometer (XPS) is used to detect the chemical information of fracture sections on PC. In terms of the generation of bubbles, the influence of glass fiber, the distribution of aluminum atoms, and the formation of new chemical bonds, this article analyses the mechanism why the two different materials can be welded successfully. The micro-anchor influence of glass giber in fiber-reinforced polymers is important. The generation of new chemical bonding (Al-O-C) between aluminum and upper PC is the main reason why the joining strength is enhanced greatly. [ABSTRACT FROM AUTHOR]

Four species of bacteria, E. coli, S. epidermidis, M. smegmatis, and P. aeruginosa, were harvested from agar nutrient medium growth plates and suspended in water to create liquid specimens for the testing of a new mounting protocol. Aliquots of 30 μL were deposited on standard nitrocellulose filter paper with a mean 0.45 μm pore size to create highly flat and uniform bacterial pads. The introduction of a laser-based lens-to-sample distance measuring device and a pair of matched off-axis parabolic reflectors for light collection improved both spectral reproducibility and the signal-to-noise ratio of optical emission spectra acquired from the bacterial pads by laser-induced breakdown spectroscopy. A discriminant function analysis and a partial least squares-discriminant analysis both showed improved sensitivity and specificity compared to previous mounting techniques. The behavior of the spectra as a function of suspension concentration and filter coverage was investigated, as was the effect on chemometric cell classification of sterilization via autoclaving. [ABSTRACT FROM AUTHOR]

ABSTRACT Additive manufacturing (AM), also commonly known as 3D printing, allows the direct fabrication of functional parts with complex shapes from digital models. In this review, the current progress of two AM processes suitable for metallic orthopaedic implant applications, namely selective laser melting (SLM) and electron beam melting (EBM) are presented. Several critical design factors such as the need for data acquisition for patient-specific design, design dependent porosity for osteo-inductive implants, surface topology of the implants and design for reduction of stress-shielding in implants are discussed. Additive manufactured biomaterials such as 316L stainless steel, titanium-6aluminium-4vanadium (Ti6Al4V) and cobalt-chromium (CoCr) are highlighted. Limitations and future potential of such technologies are also explored. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:369-385, 2016. [ABSTRACT FROM AUTHOR]

We study the formation and growth of laser-induced periodic surface structures (LIPSSs) with the finite-difference time-domain (FDTD) method. We use a recently proposed inter-pulse feedback method to account for the evolution of the surface morphology between each laser pulse sent to the surface of the processed material. This method has been used with an ablation-like mechanism, by removing material exposed to a light intensity higher than a given threshold. We propose an inverse mechanism, an expansion-like mechanism, able to grow structures that the ablation-like process cannot. This allows us to introduce the notions of constructive and destructive feedback and explains a strong contradiction between the standard Sipe-Drude theory and the experimental observations, i.e. the formation on metals of structures usually linked to wide band gap dielectrics. (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The products of the reaction of CH2OH with NO were studied by infrared diode laser spectroscopy. Products were detected to determine the branching ratios of the CH2OH + NO reaction. HNCO was detected in 10.3 ± 2% yields. No other products were detected in significant quantities, indicating that adduct formation is the primary reaction pathway. Ab initio calculations of the potential energy surface show a low energy pathway to HNCO + H2O, but no other bimolecular channels, in agreement with the experiments. [ABSTRACT FROM AUTHOR]

Highly fluorescent non-volatile fluidic fluorene derivatives functionalized with siloxane chains were synthesized and used in monolithic solvent-free liquid organic semiconductor distributed feedback lasers. The photoluminescence quantum yield values, the amplified spontaneous emission thresholds and the ambipolar charge carrier mobilities demonstrate that this class of materials is extremely promising for organic fluidic light-emitting and lasing devices. [ABSTRACT FROM AUTHOR]

Controllable, spatially inhomogeneous distributions of CdSe nanocrystals smaller than the exciton Bohr radius are grown in a glass matrix under combined action of sample heating (below the transformation temperature) and focused high-repetition femtosecond (fs) laser beam. Selective quantum dot precipitation is evidenced by position-dependent absorption and Raman spectra. The particle size is estimated as r = 2.1±0.3 nm by comparing the measured absorption and Raman spectra with those obtained from the samples grown in glass by traditional heat-treatment procedure. Direct growth of CdSe quantum dots in glass is enabled by nonlinear excitation using a focused fs duration laser beam (as differentiated from other methods), and this opens an avenue for adjustable selective growth patterns. [ABSTRACT FROM AUTHOR]

Chirped probe pulse femtosecond coherent anti-Stokes Raman scattering (CPP fs-CARS) thermometry was performed at 5 kHz in a hydrogen jet diffusion flame with an air co-flow. Measurements were performed at different heights and radial locations within the jet diffusion flame, up to 16 nozzle exit diameters downstream ( x/ d = 16). The near-nozzle measurements were characterized by large, organized, buoyancy-driven instabilities that become more chaotic at the downstream locations x/ d ≥ 4. The diffusion flame results highlight temperature fluctuations characteristic of the buoyancy-driven Kelvin-Helmholtz-type instability and provide new insights into the transient structure of these flames. At some measurement locations, the time-varying temperatures ranged from 300 K to nearly 2400 K. The CPP fs-CARS signal intensity is a factor of approximately 1000 times lower at 2400 K compared with 300 K. A dual-channel detection system was used to increase the dynamic range of the CARS measurements. The determination of temperature from the single shot spectra is discussed in detail. Laser and detection system parameters were determined from CPP fs-CARS spectra obtained from a near-adiabatic laminar calibration flame apparatus. The temperature precision of the system was determined from these calibration measurements and was found to be better than 2.0% at 2200 K. The influence of an instrument response function on spectral fitting parameters is systematically assessed. Published 2015. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Angular dependence of speckle contrast of speckle pattern projected out of a multi-mode fiber connected to a high-power blue laser module is investigated. The laser module has nine high-power InGaN/GaN blue laser diodes arranged in a three-by-three array. Each of the arrayed laser diodes have slightly different incident angle to the fiber. We have successfully extracted the fine screen speckle pattern from the projected pattern mixed up with the coarse fiber speckle pattern by processing the measured data. It is found that the speckle contrast of the both screen and fiber speckles are larger around the center area where the guided-light component closest to the paraxial direction is projected. This is because the output of the center laser in the array is likely to couple into the paraxial mode more than the rest. Speckle contrast behaviors when applying the speckle reduction methods, fiber vibration, diffuser, and spinning diffuser are also investigated. [ABSTRACT FROM AUTHOR]

We present a micro-integrated laser module based on an amplified diode laser and second harmonic generation which is a promising candidate for a green light source in next-generation 3D holographic displays. The light emitted by the amplified laser has a wavelength of 1064 nm, reaches a power up to 8.2 W and has a long coherence length of >400 m. For second harmonic generation, we tested two geometries of periodically poled lithium niobate crystals in single pass: a bulk crystal and a planar waveguide crystal. With the planar waveguide crystal, we achieve an output power >900 mW and a coherence length >20 m at a wavelength of 532 nm. [ABSTRACT FROM AUTHOR]

The aberration theory applied to co-axial optical systems is extended to off-axial systems, for which third-order aberration coefficients are considered. The derived aberrations are analyzed using three-dimensional ray bundles, spot diagrams, and image charts, and classified in relation to the system symmetry. This theory is very useful for optical designers, allowing them to clarify the relationship between the structures of off-axial optical systems and the corresponding off-axial aberrations. [ABSTRACT FROM AUTHOR]

Laser sources have been promised for many years to be better light sources as compared to traditional lamps or light-emitting diodes (LEDs) for projectors, which enable projectors having wide colour gamut for vivid image, super brightness and high contrast for the best picture quality, long lifetime for maintain free operation, mercury free, and low power consumption for green environment. A major technology obstacle in using lasers for projection has been the speckle noise caused by to the coherent nature of the lasers. For speckle reduction, current state of the art solutions apply moving parts with large physical space demand. Solutions beyond the state of the art need to be developed such as integrated optical components, hybrid MOEMS devices, and active phase modulators for compact speckle reduction. In this article, major methods reported in the literature for the speckle reduction in laser projectors are presented and explained. With the advancement in semiconductor lasers with largely reduced cost for the red, green and the blue primary colours, and the developed methods for their speckle reduction, it is hoped that the lasers will be widely utilized in different projector applications in the near future. [ABSTRACT FROM AUTHOR]

Red-emitting lasers for display applications require high output powers and a high visibility. We demonstrate diode lasers and modules in the red spectral range based on AlGaInP with optical output powers up to 1 W and a nearly diffraction limited beam. These high-luminance light sources based on tapered lasers are well suited for laser TVs and projectors for virtual reality simulators based on the flying spot technology. Additionally, we developed diode lasers with internal distributed Bragg reflector (DBR) surface gratings. These DBR tapered lasers and master-oscillator power-amplifiers based on DBR ridge-waveguide lasers and tapered amplifiers feature high power, single mode emission with coherence lengths up to several meters, which are suitable for the next-generation 3D displays based on holography. [ABSTRACT FROM AUTHOR]

A calibration method with an objective function generated from a uniform horizontal height is presented in this work for the laser plane in active vision measurement. A height target is developed with a center mark as the initial point of the uniform height. The height target is located on the horizontal plane of the 3D calibration board so that the horizontal plane is considered as the terminal of the uniform horizontal height. Based on the pinhole model of the camera and the laser plane equation, we model the objective function to find the optimal coefficients of the laser plane equation. The goal of the objective function is the smallest difference of the uniform height and the reconstructed height according to the feature points of the target. The objective function is optimized by the local particle swarm optimization. The calibrated global equation of a laser plane is obtained from the optimal value 1.153 × 10 of the objective function in the experiments. Two projective laser lines of the calibration laser plane cover the original laser lines in the image. The reconstruction errors of the calibration plane are also analyzed in discussions. [ABSTRACT FROM AUTHOR]