In this work a review of the research performed on laser ignition (LI) in internal combustion engines, especially of gasoline engines, will be presented. The path from the first demonstration of LI in an internal combustion engine to the first operation by LI of a 4-cylinder gasoline test engine and to the implementation of LI in a real automobile will be discussed. Steps taken toward developing a spark-plug-like LI system for automobile, stationary gas engines for energy cogeneration or for space applications will be described. Results on multi-point LI of methane-air mixtures in a static, constant-volume combustion chamber will be introduced, proving that multi-point LI can extend the limits of flammability. It is concluded that LI has reached a quite high degree of technical maturity and that the advantages of using LI technique versus ignition by an electrical spark plug were demonstrated.

The recent growth of the building performance research community has been in parallel with the onebuilding.org Bldg-sim email list. This list was formed in 1999 and steadily grew into a major venue for building simulation community announcements, discussions, and questions and answers (Q&A). This paper presents an analysis of the Bldg-sim email archive to determine how traffic has grown over the years and what general trends have come and gone in this particular user community. We use a text mining approach to find the most prominent topics over the years and create trend metrics from the frequency of the most common words from those topics. The results illustrate the relative rise and fall of various software tools, organizations, and simulation topics from the portion of the simulation community who used the email list. Visualizations showing the trends are presented and discussed. The paper also discusses the generalizability of results as it should be noted that the users of this email list are primarily Englishspeaking simulation practitioners from North America. All data and code used in this analysis are available in a reproducible GitHub repository.

Vector beams (VB) are optical beams with a variable polarization state on the transversal section of the beam. The more standard VB are composed of two complex conjugated modes with orthogonal polarization states. Specific applications of VB are beginning to emerge, for instance in StED Microscopy [1] or laser material processing [2] . It has been demonstrated that a particular category of VB that are composed of modes that are not complex conjugated, exhibit a rotation of the transversal profile with the propagation to the focal plane [3] . This effect is caused by the accumulation of a different amount of Gouy phase between the composing modes. This kind of beams will be further called hybrid vector beams (HVB). A recent study on the propagation of HVB demonstrated that far-field diffraction pattern may considerably change depending on the mode composition and/or polarization state [4] . We showed in [5] that a change in the mode composition of the HVB can be realized by an adjustment of the incoming polarization state on a system consisting from a spiral phase plate (SPP) and a uniaxial crystal that acts as a radially symmetric quarter waveplate.

An optical vortex (OV) has a number of intrinsic properties, such as spiral phase structure, hollow-core intensity distribution or orbital angular momentum, which leads to many interesting applications in the field of frontier research, like cold atom trapping [1] , [2] , laser-plasma interaction [3] , or communications and quantum-information coding [4] , [5] . The determination of topological charge (TC) is an important aspect for OV’s characterization. In this work, we present a procedure to determine TC of an OV by probing the spiral phase plate (SPP) element with a laser beam of a different wavelength than the one for which SPP was designed.

Structured light applications [1] , [2] require introducing a phase aberration to shape the beam for a specific purpose and with these applications, often strong focusing is involved. The demand for modeling algorithms to handle every regime of propagation is increasing. Geometrical optics do not require the full sampling of the electromagnetic field in contrast to physical optics methods, as such, beams with strong phase factors are managed more efficiently. Although it is not accurate near the focal regions, geometrical optics can be used for regions with spatial variations of the refractive index. All necessary information is the mapping function from the input to the output plane, which can be acquired via ray-tracing. Propagation to the focal plane especially in a non-paraxial regime can be realized using Debye-Wolf (DW) integral; this solution is suited for well-designed systems since does approximate the amplitude strength factor as for an ideal lens. By strength factor of a ray, first defined in [3] , we refer to the Jacobian determinant of the ray mapping from the input to the output plane. A generalized version of DW that evaluates the amplitude strength factor numerically from the second-order derivatives of the phase function was described in [4] , this being valid also when stronger aberrations are present.

We design and investigate an original optical component made of a c-cut uniaxial crystal and an optical system to generate cylindrical vector beams with an adjustable polarization state. The original optical component has a specific, nearly conical shape which allows it to operate like a broadband wave retarder with the fast axis oriented radially with respect to the optical axis. We show via numerical simulations, using the Debye–Wolf diffraction integral, that the focal spot changes depending on the polarization state, thus enabling the control of the focal shape. Non-symmetrical shapes can be created although the optical system and incoming beam are circularly symmetric. We explained, using Jones matrix formalism, that this phenomenon is connected with the Gouy phase difference acquired by certain modes composing the beam due to propagation to the focal plane. We present our conclusions in the context of two potential applications, namely, stimulated emission depletion (STED) microscopy and laser micromachining. The optical system can potentially be used for STED microscopy for better control of the point-spread function of the microscope and to decrease the unwanted light emitted from the surroundings of the focal point. We give an analytical expression for the shape of the original component using the aspherical lens formula for the two versions of the component: one for each potential application.

We designed and analyzed an optical component that works as a radially symmetric wave-plate and an associated optical system to control the polarization state of the beam, which as a consequence, change the shape of the focal spot.

A 5.0-at.% Nd-doped La0.64Gd0.41Sc2.95(BO3)4 (Nd:LGSB) borate laser crystal was successfully grown by the Czochralski method, for the first time to our knowledge. The spectroscopic properties of the grown crystal are discussed and 1 µm laser emission, under end-pumping with a fiber-coupled diode laser at 807 nm, is reported. A c-cut Nd:LGSB medium yielded 1.35 W continuous-wave output power at 0.63 overall optical-to-optical efficiency, with respect to the absorbed pump power, together with the high 0.68 slope efficiency. With an a-cut Nd:LGSB sample, 0.81 W output power at 0.52 optical-to-optical efficiency was obtained. The laser emission performances under quasi-continuous wave pumping are presented as well, for both c-cut and a-cut crystals. Passive Q-switching was investigated with a semiconductor saturable absorber mirror (SESAM). Laser pulses with 2.2 µJ energy and 32.8 ns durations were recorded from a-cut Nd:LGSB. The average output power reached 0.36 W at 1.55 W absorbed pump power. Passive mode-locking with SESAM was achieved in a long Z-type resonator. Ultrashort pulses with 0.19 W average power, 1.63 nJ energy, and 1.43 ps pulse duration, at 118 MHz repetition rate, are demonstrated for the a-cut Nd:LGSB medium.

In this work we report on the output performances of a Nd:YVO4 picosecond (ps) laser oscillator that was passively modulated by different semiconductor saturable absorber mirrors (SESAMs). The laser emission characteristics are given for SESAM used in Z-type and W-type cavities under similar pumping conditions. Q-switch mode-locking (QML) regime was obtained in the Z-type resonator whereas the W-type oscillator enabled stable mode-locking (ML) operation. For the W-type cavity ML performances are reported for two SESAMs with distinct parameters. Thus the use of a SESAM with 10 ps long recovery time allowed ML operation with pulses of 11.1 nJ energy and 15 ps duration (0.74 kW peak power) at 158 MHz repetition rate; the average power at 1.06 mu m was 1.75 W for 5.17 W pump power at 809 nm. Employing a second SESAM with 0.5 ps short recovery time, the Nd:YVO4 laser yielded pulses with increased 13.4 nJ pulse energy and shorter, 12.5 ps, duration (1.1 kW peak power) at 158 MHz repetition rate, corresponding to 2.11 W average power; the pump power was 5.09 W. The results highlight the significant role of the SESAM parameters as well as of the implemented cavity design for the construction of a ps laser source of high performance.

We report the first results on 1.06-μm mode-locking performances of a Czhochralski-grown a-cut Nd:LGSB, uncoated medium. Ultrashort pulses of 1.43 ps, at 118-MHz repetition rate are achieved with a Z resonator and SESAM approach.

Alternative propellant combinations for orbital manoeuvring system and reaction-control system require new ignition devices for a new generation of thrusters.Such thrusters need to withstand large, from hundred to thousand range, number of cycles.Additional requirements are concerning the replacement of the toxic propellants with green ones.The classical methods of ignition are based on pyrotechnical and electrical effects.Recently, a lot of efforts are made to develop an alternative ignition technology based on solid-state lasers [1].The energy required for a reliable ignition depends on the working conditions and one alternative to single highenergy laser pulse is a multiple-pulse laser system that allows the focusing of several pulses in a small volume.Single and multipoint ignition [2-5] has been also studied for car engine ignition.In this work we are reporting on the realization of a compact laser that delivers four independent output beams.The device, shown in Fig. 1a, is made of a composite Nd:YAG/Cr 4+ :YAG structure.Monolithically resonator was obtained by coating the high-reflectivity mirror on Nd:YAG input side and the out-coupling mirror on the exit surface of Cr 4+ :YAG.

According to the global research of high-power laser gain media able to substitute monocrystalline materials or even expand the possibilities offered by them, the main research of this study was focused on synthesis of laser materials based on Nd3+:YAG and Sm3+:YSAG transparent ceramics by solid-state reaction and vacuum sintering method, with high absorption and low residual diffusion.

A laser configuration made of a thin-disk Nd:YAG/YAG composite medium that consists of a circular Nd: YAG core bonded by diffusion to a circular undoped YAG and that has the shape of a plane-concave lens is presented. The pump is done through the undoped YAG edge, in a three-fold scheme, directly from the diode-laser optical fibers. Such a laser was built employing a Nd:YAG/YAG ceramics made of a 1.0-at.% Nd:YAG core of 2.0-mm diameter surrounded by a 10 mm in diameter YAG. The thickness was 180 mu m at the center of Nd:YAG and 500 mu m at the YAG edge. The Nd:YAG/YAG medium was attached to a water-cooled copper finger. At 2 Hz repetition rate the laser yielded pulses at 1.06 mu m with energy E-p = 31.8 mJ under the pump at 807 nm with total energy E-pump =114.6 mJ; the slope efficiency was 0.31. A decrease of laser pulse energy with the repetition rate was observed. This indicates that a better thermal management, which could be made through metallic bonding of Nd:YAG/YAG to the cooling system, is necessary. (C) 2017 Elsevier Ltd. All rights reserved.

We developed a combination of technology for deposition contacts/wires upon nanoporous InP thin film structures and RF sputtering InP films. Indium phosphide (InP) films were deposited onto glass substrate using RF magnetron sputtering by varying the substrate temperature (50–100 °C), under constant argon pressure (6.3·10−3Bar) and RF power (100 W). To have good optimisation of growing parameters of LT-InP films we use several characterization techniques, Raman, FTIR, XRD, and THz spectroscopy, respectively. Doping with Ga ions was used to induce disordered in InP film, to reduce the optical recombination in IR spectra.

Characteristics of fuel-air mixture combustion in a naturally aspired spark-ignition engine with indirect injection that was ignited by classical spark plug as well as by laser sparks are presented. Differences between the duration of combustion, defined by the main burning heat release angles at 10% and 90% of the total heat, are discussed for these two types of ignition.

Performance and exhaust emissions of spark ignition engines are strongly dependent on the development of the combustion process. Controlling this process in order to improve the performance and to reduce emissions by ensuring rapid and robust combustion depends on how ignition stage is achieved. An ignition system that seems to be able for providing such an enhanced combustion process is that based on plasma generation using a Q-switched solid state laser that delivers pulses with high peak power (of MW-order level). The laser-spark devices used in the present investigations were realized using compact diffusion-bonded Nd:YAG/Cr4+:YAG ceramic media. The laser igniter was designed, integrated and built to resemble a classical spark plug and therefore it could be mounted directly on the cylinder head of a passenger car engine. In this study are reported the results obtained using such ignition system provided for a K7M 710 engine currently produced by Renault-Dacia, where the standard calibrations were changed towards the lean mixtures combustion zone. Results regarding the performance, the exhaust emissions and the combustion characteristics in optimized spark timing conditions, which demonstrate the potential of such an innovative ignition system, are presented.

A Renault vehicle with gasoline indirect injection engine was fully operated with laser spark plugs that were build using high-peak power passively Q-switched Nd:YAG/Cr4+:YAG lasers. Some performances of the engine, including cycling variability, specific emissions or brake specific fuel consumption were measured at various speeds and loads.

We report on the design, realization, and output performance of a diode-pumped high-peak-power passively Q-switched Nd:YAG/Cr4+:YAG composite medium monolithic laser with four-beam output. The energy of a laser pulse was higher than 3 mJ with duration of 0.9 ns. The proposed system has the ability to choose independently the focus of each beam. Such a laser device can be used for multipoint ignition of an automobile gasoline engine, but could also be of interest for ignition in space propulsion or in turbulent conditions specific to aeronautics. (C) 2016 Chinese Laser Press

The reasearch main objective is to obtain ceramic laser materials based on pure YAG (Y3Al5O12) and Nd doped YAG (Y-3-xNdxAl(5)O(12), with x = 0.5 and 1.0 at. %), by conventional solid state reaction method. Stoichiometric compositions of Y3Al5O12 (YAG), Y2.985Nd0.015Al5O12 (0.5 at.% Nd: YAG) and Y2.97Nd0.03Al5O12 (1.0 at.% Nd: YAG) were prepared using high purity Y2O3 (99.999%), Al2O3 (99.999%) and Nd2O3 (99.999%) nanopowders. Green bodies were sintered at 1750 degrees C for 16 h under vacuum (1.0 x 10(-3) Pa) and then annealed at 1450 degrees C for 10 h in the air.