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Abstract Time-correlated single-photon counting (TCSPC) is one of the most active technologies for optical time-of-flight ranging and three-dimensional (3D) imaging. Ranging accuracy is one of the most critical issues of lidar system. We propose a three-laser-beam TCSPC lidar system. Besides the main measuring laser beam, the second beam is used to decrease the error caused by jitter of time synchronization. The third beam has n+0.5 time bins’ difference with the main measuring beam, and it is used to correct the error caused by the discrete sampling of time-to-digital converter (TDC). To validate the feasibility of the three-laser-beam TCSPC lidar system, a series of simulation experiments using the scheme is carried out. The results show that this method is effective to improve the ranging accuracy of TCSPC lidar system. [ABSTRACT FROM AUTHOR]

We propose a linearly frequency-tuning single-frequency Nd:YVO laser. We achieve a single-frequency tuning operation with a tuning range of 6.3 GHz and a maximum power of 0.5 W at 1,064 nm by tilting a thin coated etalon and changing the voltage applied to an RTP crystal in a synchronous way. The laser is linearly tuned with a standard frequency variation of ∼190 MHz. We estimate the average tuning speed to be 0.81 GHz/s. The tuning range obtained is more than three times the longitudinal mode spacing of the laser resonator. [ABSTRACT FROM AUTHOR]

Abstract: The investigation elucidates electrochemical effect on tungsten (W) contact plugs and proposes front-end-of-the-line semiconductor manufacture processes that are responsible for corrosion involving source/drain implants, rapid thermal anneal (RTA) and nickel silicide (Ni x Si x ). W-filled contacts are commonly used in submicron and even nanometer CMOS technology, and the integrity of W contact plugs becomes increasingly critical as transistors continue to shrink. Incomplete W plugs with a recess on the tops of the contacts were observed in N+/n-well locations following W chemical mechanical polishing (WCMP). This phenomenon arises from anodic corrosion since the under-layer P+/p-well and N+/n-well form a PN junction structure, which has built-in potential and promotes the movement of photo-generated electrons during WCMP. The mechanism of the electrochemical effect is elucidated, and a series of experiments indicates a thin Ni x Si x layer, a heavy dosage of source/drain implants and a high RTA temperature promote the formation of corrosion defects. [Copyright &y& Elsevier]

Abstract: In this paper, solid dye samples were prepared by codoping laser dyes Pyrromethene 567 (PM567) as the energy donor and Rhodamine 610 (Rh610) as the energy acceptor into the ethanol modified poly (methyl methacrylate) matrix (MPMMA) to enhance the properties of the solid dye lasers. The fluorescence intensity of the acceptor was enhanced by up to 9 fold with the introduction of the donor molecules. The laser efficiency of the dye mixture doped samples was improved by up to 8 times relative to that of the samples solely doped with the acceptor, and the highest slope efficiency was obtained as 70.4%. The radiative and nonradiative energy transfer rate constants (K R and K NR ) were calculated using the Stern–Volmer plots and the acceptor concentration dependence of the radiative and nonradiative transfer efficiencies were also obtained. The K R was three orders of magnitude higher than the K NR , indicating the dominance of the radiative energy transfer mechanism in the present system. The deviation of the Stern–Volmer plot from the linearity demonstrated that both the dynamic and transient quenching mechanism exist in the present energy transfer system. [Copyright &y& Elsevier]

Abstract: We propose an innovative voltage-contrast (VC) inspection approach for detection and verification of the process window for contact-to-poly overlaying. The method uses alternative scans for inline detection of leakage induced by underneath overlay drift. Conventional optical inspection with box-in-box or bar-in-bar test structures cannot accurately indicate the overall overlay performance for all chip locations as geometries continue to shrink. An e-beam inspection system with VC contrast imaging was introduced during a recent technology update. The alternative e-beam system with positive and negative charging modes was set up to perform dual scans for sensitive pMOS and nMOS detection. Although positive-mode scanning can detect pMOS leakage on the surface, it indicates a normal subsurface with no leakage. Defects can only be identified by another scan in negative mode to detect contact-to-poly misalignment in the neighboring nMOS. Leakage electrons affect each other as they spread through poly lines crossing p/nMOS. The principle and mechanisms for leakage defects were verified in a series of corrective actions for misalignment. The methodology allows inline detection instead of end-of-line electrical testing and de-layered analysis. This greatly shortens the response time and facilitates yield learning. [Copyright &y& Elsevier]

Abstract: The effects of pressure and laser energy on the excitation temperature, electron number density and spark energy of laser induced plasmas (LIPs) in nitrogen were investigated using an ungated spectrometer with an electron multiplying charge-coupled device (EMCCD) camera as the detector. The plasmas were generated in nitrogen of 1.2×104 Pa to 1.0×105 Pa by 532nm output of a 10Hz Q-switched Nd:YAG laser with pulse energy ranging from 20mJ to 100mJ. The excitation temperatures were found around 3eV, and varied little with pressure and laser energy. The electron number densities increased from 5.8×1017 cm−3 to 4.7×1018 cm−3 when the pressure was increased from 1.2×104 Pa to 1.0×105 Pa, but varied little with laser energy. The spark energy increased linearly with the input laser energy, and saturated at 35–60% of the input energy. Comparisons with results of time-resolved measurements and of other authors indicate that the ungated spectrometer can give reasonable results on excitation temperature and electron number density of LIPs, although it suffers intrinsic limitations involved with its inability to be time-resolved, and can serve as an option to lower systematic cost for practical applications of laser induced plasmas. [Copyright &y& Elsevier]

Abstract: Based on ultrafast laser pulses, time-resolved resonance enhancement coherent anti-Stokes Raman scattering (RE-CARS) is applied to investigate wave-packet dynamics in gaseous iodine. The effects of air pressure on the wave-packet dynamics of iodine molecules are studied at pressures ranging from 1.5Torr to 750Torr. The RE-CARS signals are recorded in a gas cell filled with a mixture of about 0.3Torr iodine in air buffer gas at room temperature. The revivals and fractional revival structures in the wave-packet signal are found to gradually disappear with rising air pressure up to 750Torr, and the decay behaviors of the excited B-state and ground X-state become faster with increasing air pressure, which is due to the collision effects of the molecules and the growing complexity of the spectra at high pressures. [Copyright &y& Elsevier]

Abstract: We utilize femtosecond time-resolved electronic resonance-enhanced coherent anti-Stokes Raman scattering (ERE-CARS) to investigate new information for pyrromethene 650 (PM650) dye molecules. For this purpose, the vibrational properties of PM650 are registered in diluted solutions of several organisms. We observe a strong Raman vibrational mode with a wavenumber difference of about 48cm−1 in its organic solutions. This may be linked to the intramolecular electron transfer (ICT) process from the aromatic ring to the cyano group in PM650. The influence of the solvent effects on the vibrational dynamics of PM650 is also investigated. The vibrational properties of PM650 dye molecules diluted in polar organic solutions are light solvent-dependent. [Copyright &y& Elsevier]

Abstract: In this paper, ultrafast time-resolved coherent degenerate four-wave-mixing (DFWM) spectroscopy is performed to investigate molecular dynamics in the gaseous phase. Laser pulses lasting for 40fs are used to create and monitor different vibrational eigenstates of iodine at room temperature (corresponding to a low saturation pressure of about 35Pa). Using an internal time delay in the DFWM process resonant with the transition between the ground X-state and the excited B-state, the vibrational states of both the electronically excited and the ground states are detected as oscillations in the DFWM transient signal. The dynamics of either the electronically excited or ground state of iodine molecules obtained are consistent with the previous high temperature studies on the femtosecond time-resolved DWFM spectroscopy. [Copyright &y& Elsevier]

Abstract: Solid-state dye samples based on modified copolymers of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) with methanol doped with PM567 were first prepared. The volume proportions of methanol have great effects on the laser''s characteristics including spectra, lasing output and thermal properties. The highest slope efficiency of 64.25% was achieved in the sample MP (MMA:HEMA=85:15+10% methanol). Pumping the samples at a repetition rate of 5Hz with a pulse energy as high as 100mJ (the fluence was 0.26J/cm2), the maximum lifetime of 278,000 shots was obtained in the sample MP (MMA:HEMA=85:15+15% methanol), and the corresponding normalized photostability reached 180.7GJ/mol. The obtained ten-shots damage thresholds were as high as 6.7J/cm2. The results indicate that the laser properties of solid-state dyes can be greatly enhanced by using modified copolymers of MMA and HEMA with methanol as solid hosts. [Copyright &y& Elsevier]

This paper describes a high-pulse-energy frequency-doubled ultraviolet dye laser operating at a repetition rate of 500 Hz. The pump source is a laser-diode side-pumped Q-switched Nd:YAG laser with a pulse energy of 29 mJ at 532 nm. A master oscillator power amplifier is employed to amplify the output pulse of the dye laser to 8.1 mJ at 566 nm, and by frequency doubling with BBO crystal a pulse energy of 1.7 mJ at 283 nm is achieved with a pulse width of 8 ns. This is more than four times the largest reported pulse energies generated by other fixed-frequency dye lasers when operating at repetition rates of more than 1 kHz. The conversion efficiency and stability of dye laser are discussed, which show the potential for high-speed laser diagnostics in the fields of combustion and turbulent flow detection. [ABSTRACT FROM AUTHOR]

In this paper, discrimination of soft tissues using laser-induced breakdown spectroscopy (LIBS) in combination with multivariate statistical methods is presented. Fresh pork fat, skin, ham, loin and tenderloin muscle tissues are manually cut into slices and ablated using a 1064 nm pulsed Nd:YAG laser. Discrimination analyses between fat, skin and muscle tissues, and further between highly similar ham, loin and tenderloin muscle tissues, are performed based on the LIBS spectra in combination with multivariate statistical methods, including principal component analysis (PCA), k nearest neighbors (kNN) classification, and support vector machine (SVM) classification. Performances of the discrimination models, including accuracy, sensitivity and specificity, are evaluated using 10-fold cross validation. The classification models are optimized to achieve best discrimination performances. The fat, skin and muscle tissues can be definitely discriminated using both kNN and SVM classifiers, with accuracy of over 99.83%, sensitivity of over 0.995 and specificity of over 0.998. The highly similar ham, loin and tenderloin muscle tissues can also be discriminated with acceptable performances. The best performances are achieved with SVM classifier using Gaussian kernel function, with accuracy of 76.84%, sensitivity of over 0.742 and specificity of over 0.869. The results show that the LIBS technique assisted with multivariate statistical methods could be a powerful tool for online discrimination of soft tissues, even for tissues of high similarity, such as muscles from different parts of the animal body. This technique could be used for discrimination of tissues suffering minor clinical changes, thus may advance the diagnosis of early lesions and abnormalities. [ABSTRACT FROM AUTHOR]

In this paper, a ground target extraction system for a novel LiDAR, airborne streak tube imaging LiDAR (ASTIL), is proposed. This system depends on only a single echo and a single data source, and can achieve fast ground target extraction. This system consists of two modules: Autofocus SSD (Single Shot MultiBox Detector) and post-processing. The Autofocus SSD proposed in this paper is used for object detection in the ASTIL echo signal, and its prediction speed exceeds that of the original SSD by a factor of three. In the post-processing module, we describe in detail how the echoes are processed into point clouds. The system was tested on a test set, and it can be seen from a visual perspective that satisfactory results were obtained for the extraction of buildings and trees. The system mAPIoU=0.5 is 0.812, and the FPS is greater than 34. The results prove that this ASTIL processing system can achieve fast ground target extraction based on a single echo and a single data source. [ABSTRACT FROM AUTHOR]

The research aims at nonvisual defects causing the poly gate leakage failure and the corresponding inline voltage-contrast (VC) inspection. Electron beam inspection (EBI) begins to be frequently used for scanning either SRAM or DRAM cell area in nano-scaled technologies. The research, furthermore, extends EBI to logical area of an ASIC product and proposes an inline detectable methodology for gate leakages. Extreme tiny and nonvisual residues could happen during gate etch processes by the step height between active area (AA) and shallow trench isolation (STI), and the tiny defects are difficult to be located even some of those did lead to chip probe (CP) test failure. The subsequent implant processes would punch through those tiny poly residues, make the residue being conductive, and finally electrons on the gate would leak to the ground through the residue. Those nonvisual residues act as bridges for gate leakages. EBI with designed positive charging modes was applied into the series of implement steps and found the leakage by a significant voltage contrast signal post the source/drain implantation. The bright VC of the gate poly implied the leakage electrons charging on the gate. A series of process experiments based on the model for reducing leakages was tested and quickly verified by the EBI in front end of the line. An optimal process integration condition was soon carried out with a significant chip yield enhancement. [ABSTRACT FROM AUTHOR]

Abstract: The molecular dynamics process is investigated in this paper using a broadband fs time-resolved coherent anti-Stokes Raman spectroscopy (CARS) technique. By varying the timing of laser pulses, low vibrational states are started and studied on both the electronically excited B(3 Π 0u +) state and ground X(1 Σ 0g +) state of iodine in the gas phase at room temperature. According to change the pump wavelength or Stokes pulse as well as the wavelength of the detection window for the CARS signal, dynamics on different potential-energy surfaces can be accessed and detected by the CARS spectroscopy. Results show that the period of the oscillation is decreased for the excited B(3 Π 0u +) state as the wavelength of the pump pulses is increased, while it is increased for the ground X(1 Σ 0g +) state with the increase of the Stokes wavelength. [Copyright &y& Elsevier]

We study laser performance with two laser dyes, Pyrromethene 567 and Rhodamine 610, co-doped into modified poly(methyl methacrylate) (MPMMA). We achieve a more than 37 nm wide tunable range. We obtain a narrowband-laser slope efficiency of 27.24%, which is almost as high as a broadband-output slope efficiency of 36.6%. To the best of our knowledge, the narrowband slope efficiency is the highest under the same conditions so far. The narrowband laser linewidth obtained is far less than 0.3 nm. All our results indicate that high laser performance can be achieved using two dyes co-doped into MPMMA. [ABSTRACT FROM AUTHOR]

Abstract: The two-photon absorption (TPA) characteristics of PMMA discs doped with three different dyes were studied using an fs-pulsed Ti-Sapphire laser as the pump source, and employing the open-aperture Z-scan technique. TPA cross-sections obtained for PMMA doped with the dyes PM597, DCM and rhodamine 6G–rhodamine B (co-doped) were found to be equal to 24.7, 33.3 and 32.3GM, respectively (1GM=10−50 cm4 sphot−1 mol−1). Furthermore, two-photon fluorescence was measured for the samples containing DCM and rhodamine 6G–rhodamine B (co-doped). Compared to the one-photon fluorescence spectrum, the peaks in the two-photon fluorescence spectrum were red shifted and the extent of red shift increased with increasing doping concentration. We have also observed that the red shift in the two-photon fluorescence peak of the samples in the solid form is much larger than that in the solution state. This phenomenon could be explained by a twisted intra-molecular charge transfer model. [Copyright &y& Elsevier]

In order to solve the difficulty of characterizing the optical constants of ZnS at high temperatures, the multi-phonon absorption dielectric function model which includes temperature parameters is constructed and modified in this paper. The multi-phonon absorption parameters of ZnS have been inverted based on variable temperature infrared transmittance spectra. The variable temperature infrared transmittance spectra of ZnS have been well fitted. The temperature dependence of the dissociation energy of ZnS materials is demonstrated, and the optical constants of the ZnS material have been obtained at 25 °C, 100 °C, 200 °C, 300 °C, and 400 °C. • The relationship between the value of m max and temperature is established in the multi-phonon absorption model of ZnS. • The ZnS multi-phonon parameters for various temperatures obtained by spectral inversion conform to physical laws. • Highly accurate variable-temperature optical constants of ZnS were obtained based on the multi-phonon absorption model. [ABSTRACT FROM AUTHOR]

We demonstrate the presence of femtosecond laser induced charge transfer in Ne+-He collisions. Electron transfer in ion-atom collisions is considerably modified when the collision is embedded in a strong laser field with the laser intensity of ∼1015 W/cm2. The observed anisotropy of the He+ angular distribution confirms the prediction of early work that the capture probability varies significantly with the laser polarization angle. [ABSTRACT FROM AUTHOR]

We present a simple method to gradually tune the size and to induce the shape change of CeO2nanoparticles viaincreasing the content of Yb3+doping. [ABSTRACT FROM AUTHOR]

Highlights • A burst-mode MOPA frequency-tripled Nd:YAG laser at 355 nm is presented. • Ultraviolet pulses with high energy and high repetition rate are achieved. • In-house designed 5-bar LD pump modules improve laser intensity distribution. • Suitable for plenty of applications like pumping dye lasers and PLIF imaging. Abstract We demonstrated a Nd:YAG based Q-switched burst-mode MOPA laser with frequency-tripled ultraviolet output by nonlinear harmonic generation. The individual pulse energy of 13.4 mJ with a repetition rate of 10 kHz at 355 nm was obtained. The short pulse width of ∼10 ns provides a high peak power up to 1.3 MW at 355 nm. This high-energy and high-repetition-rate ultraviolet source has the potential in applications such as pumping the dye laser systems for PLIF imaging. [ABSTRACT FROM AUTHOR]

Highlights • A pulse-burst dye laser at 10 kHz repetition rate is presented for the first time. • Single pulse energy achieves 1.45 mJ at 280 nm at 10 kHz repetition rate. • Frequency doubling efficiency is higher than previous laser at this repetition rate. • OH-PLIF images are taken and show the promising application. Abstract In this paper, we present a dye laser operated under burst mode with minimum pulse interval 0.1 ms, corresponding to repetition rate 10 kHz. Pulse energy of 7.77 mJ with efficiency of 26.7% is achieved at 560 nm by using rhodamine 6G solution in methanol as the gain medium when the energy of pump energy is 32.4 mJ at 532 nm. The tunable range is found from 545.3 nm to 573.1 nm for fundamental and 272.5 nm to 286.9 nm after frequency doubling with maximum pulse energy 1.45 mJ at 280 nm, which indicates the frequency doubling efficiency is 18.7%. OH-PLIF images with time interval 0.1 ms are gotten using the dye laser, which proves the feasibility of this dye laser applied in dynamic laser diagnosis fields. [ABSTRACT FROM AUTHOR]

Abstract TCSPC technique requires that the signal should be weak with average numbers of photons in one signal period being less than 0.01 to 0.1 in order to ensure the accuracy. If the signals are stronger, the photon pile-up will lead to range walk errors. In this paper, the range walk errors of TCSPC lidar using photomultiplier tube caused by the amplitude change and distortion of reconstructed laser waveform are theoretically analyzed. A correction method for the errors under strong signal situations is proposed and validated in a laser ranging experiment. The results show that, using the correction method, range walk errors can be reduced from 183mm to 6mm for the case when the average number of photons detected is 9.6 and the distance of the target is ∼ 4.8m. The applicable returned signal domain of the TCSPC technique has been extended up to 10 photons per signal period, which has been improved by two orders of magnitude compared to the conventional weak signals. [ABSTRACT FROM AUTHOR]

The research discussed the application of planar laser-induced fluorescence technique for visualizing the flow over an airfoil at different Reynolds numbers and angles of attack. The proposed arrangement allows visualizing the development process of the flow field structure around the airfoil. The focus of the study is the influence of the angles of attack and the Reynolds number on the separation boundary layer, which causes the wake vortex or separation bubble. Compared with the traditional visualization technology, the technology of planar laser-induced fluorescence has better time resolution (50 ns) and followability (Reynolds number = 219,500). In order to achieve high-speed flow field visualization, planar laser-induced fluorescence provides a reliable means of measurement to solve the related engineering problems. [ABSTRACT FROM AUTHOR]

Micro-structured surface on diamond is widely used in microelectronics, optical elements, MEMS and NEMS components, ultra-precision machining tools, etc. The efficient micro-structuring of diamond material is still a challenging task. In this article, the influence of the focus position on laser machining and laser micro-structuring monocrystalline diamond surface were researched. At the beginning, the ablation threshold and its incubation effect of monocrystalline diamond were determined and discussed. As the accumulated laser pulses ranged from 40 to 5000, the laser ablation threshold decreased from 1.48 J/cm 2 to 0.97 J/cm 2 . Subsequently, the variation of the ablation width and ablation depth in laser machining were studied. With enough pulse energy, the ablation width mainly depended on the laser propagation attributes while the ablation depth was a complex function of the focus position. Raman analysis was used to detect the variation of the laser machined diamond surface after the laser machining experiments. Graphite formation was discovered on the machined diamond surface and graphitization was enhanced after the defocusing quantity exceeded 45 µm. At last, several micro-structured surfaces were successfully fabricated on diamond surface with the defined micro-structure patterns and structuring ratios just by adjusting the defocusing quantity. The experimental structuring ratio was consistent with the theoretical analysis. [ABSTRACT FROM AUTHOR]

Broadband femtosecond time-resolved coherent anti-Stokes Raman scattering ((TR-CARS)) is utilized to investigate the wave-packet dynamics of Cresyl Violet (CV670) dye molecules in ethanol solvent at room temperature. An interesting behavior of wave-packet dynamics phenomena is observed and discussed for the first time, and several unknown Raman vibrational modes with frequency differences of 32 cm −1 , 38 cm −1 , 45 cm −1 , 50 cm −1 , 55 cm −1 , 65 cm −1 , 80 cm −1 , 95 cm −1 and 101 cm −1 are excited and obtained at the same time. This work makes possible high efficiency in the structure investigation as well as dynamics of intra-molecular processes by broadband femtosecond (TR-CARS) spectroscopy with fast Fourier transformation (FFT) analysis means. [ABSTRACT FROM AUTHOR]

Optical constants and micro-structure characteristics of SiO 2 films deposited by ion beam sputtering were studied. The samples were prepared on substrates of silicon and silica with different oxygen flow rates ranged from 0 sccm to 40 sccm with a step of 10 sccm. Refractive index of the samples were obtained by spectra inversion technique. It's suggested that the value of refractive index presents first decrease and then increase as the oxygen flow rate larger, and the turning point is about 30 sccm both at 0.633 μm and 10.6 μm. And the SiO 2 thin films were confirmed all amorphous structure by the XRD measurement. The proportion of hydroxyl in SiO 2 thin film were determined by XPS, which is beneficial to analyze the film defects. Also the Si-O-Si angle and vibration frequency in TO mode and LO mode were researched by FTIR spectra. [ABSTRACT FROM AUTHOR]

Tunable all-solid-state lasers are increasingly employed, and there has not been a relatively comprehensive paper discussing these lasers. This paper will describe several frequency-modulation approaches applied to the tunable all-solid-state single-longitudinal-mode laser, including their characteristics and researches. It could be hoped to provide a reference for those researchers about intracavity frequency modulation in all-solid-state lasers. [ABSTRACT FROM AUTHOR]

Laser-induced plasma ignition has been applied in various combustion systems, however, work on flame stabilization with repetitive laser-induced plasma (LIP) is rather limited. In this paper, stabilization of a premixed methane-air flame with a high repetition nanosecond LIP is reported. The plasma energy coupling and the temporal evolution of the flame kernels generated by the LIPs are investigated with different laser repetition rates, i.e., 1 Hz, 100 Hz and 250 Hz, respectively. The plasma energy coupling is not affected in the air flow and in the premixed methane-air flow with the applied laser repetition rates. Continuous combustion flame stabilization has been achieved with LIPs of 100 Hz and 250 Hz, in terms of catch-up and merging of the consecutive flame kernels. The flame kernel formed by the last LIP does not affect the evolution of the newly formed flame kernel by the next LIP. The catch-up distance, defined as the distance from the LIP initiation site to the flame kernel catch-up position, is estimated for different laser repetition rates based on the temporal evolution of the flame kernels. A higher laser repetition rate will lead to a shorter catch-up distance which is beneficial for flame stabilization. The up limit for the laser repetition rate to realize effective flame stabilization is determined from the critical inter-pulse delay defined from the onset of the LIP to the return of the initially contraflow propagating lower front to the LIP initiation site. The up limit is 377 Hz under the flow conditions of this work (equivalence ratio of 1, flow speed of 2 m/s, and Reynolds number of 1316). [ABSTRACT FROM AUTHOR]

In this paper, a 100 Hz planar laser-induced fluorescence system based on the off-shelf commercial laser and self-made intensified camera is presented, which is low cost and maintainable to be applied in practical combustion research. By using this device, 100 Hz continuously planar laser-induces fluorescence laser combustion diagnostics was conducted. To evaluate this device, both laboratorial combustors and a scramjet combustor were studied. In these experiments, the structure of flame and expansion and the oscillation process of combustion can be resolved. [ABSTRACT FROM AUTHOR]

• A stable, high-pulse-energy laser based on Multisegmented Nd:YAG was proposed. • 13.2 mJ, 6.4 ns laser pulses at 532 nm was achieved at 2 kHz repetition rate. • The stability of the pulsed 532 nm laser was investigated in environmental test. In this paper, a high-stability, high-pulse-energy laser at a repetition rate of 2 kHz was presented from an electro-optically Q-switched Nd:YAG master oscillator power amplifier (MOPA) system. A multi-segment composite Nd:YAG crystal was utilized as the gain medium of the electro-optically Q-switched laser, yielding a pulse energy of 8.6 mJ and a pulse width of 7.8 ns at 2 kHz. By using two laser diode (LD) end-pumped Nd:YAG amplifiers, the single pulse energy was amplified to 28.6 mJ, corresponding to a peak power of 3.7 MW. By frequency doubling with a LiB 3 O 5 (LBO), 13.2 mJ and 6.4 ns laser pulses were achieved at 532 nm. With the temperature varying from −40℃ to 55℃, the coefficient of variation (CV) of the pulse energy was 2.6%. Besides, the laser system also presented high stability under the typical vibration condition of the airborne platform. This MOPA laser system is a promising laser source for airborne remote sensing. [ABSTRACT FROM AUTHOR]

• A new remote sensing detection equipment, airborne streak tube imaging laser radar. • A building zone extraction method from airborne streak tube imaging laser radar data. • A building zone extraction method only using single data source, laser radar data. • Extracting suburban residential building zone. In this paper, we proposed a novel method for extracting suburban residential building zone (SRBZ) from airborne streak tube imaging LiDAR (STIL) data. This method is implemented using a single data source, which avoids the collections of multi-source data and shortens the production cycle of LiDAR data products. The framework of the method is mainly composed of a prediction module, and a correction module. In the correction module, two correction algorithms were proposed, that is, k -nearest neighbor majority voting correction algorithm (k- NNMV) and Gaussian weight based k -nearest neighbor voting correction algorithm (GW k- NNV). Experiment tests show that the framework based on the GW k -NNV has a better SRBZ extraction effect than that of the k -NNMV. The F 1 coefficient of the GW k -NNV-based framework reached 80.10%. That proves that the proposed method for extracting SRBZ from airborne STIL data is feasible. [ABSTRACT FROM AUTHOR]

In this letter, a tunable Ti:sapphire laser pumped by a frequency-doubled Q-switched Nd:YAG laser at a repetition rate of 10 Hz is demonstrated. By using two dense flint glass prisms as dispersion element, a tuning range from 745 to 855 nm with a linewidth of 0.8 nm (FWHM) was achieved. At an incident pump energy of 40 mJ, the maximum output energy was 5.5 mJ at 800 nm with a pulse width of 23.8 ns (FWHM), which led to a slope efficiency of 36.4% from the 532 nm pump laser to the Ti:sapphire laser. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:855-856, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25860 [ABSTRACT FROM AUTHOR]

A compact high-peak-power, high-repetition-rate burst mode laser is achieved by an acousto-optical Q-switched Nd:YVO 1064 nm laser directly pumped at 878.6 nm. Pulse trains with 10-100 pulses are obtained using acousto-optical Q-switch at repetition rates of 10-100 kHz under a pulsed pumping with a 1 ms duration. At the maximum pump energy of 108.5 mJ, the pulse energy of 10 kHz burst mode laser reaches 44 mJ corresponding to a single pulse energy of 4.4 mJ and an optical-to-optical efficiency of 40.5 %.The maximum peak power of ~468.1 kW at 10 kHz is obtained with a pulse width of 9.4 ns. The beam quality factor is measured to be M ~1.5 and the pulse jitter is estimated to be less than 1 % in both amplitude and time region. [ABSTRACT FROM AUTHOR]

We present a compact high-peak-power, high-repetition-rate burst-mode laser from a master-oscillator power amplifier (MOPA) at 1064 nm for laser-based measurement applications. The oscillator is an 808 nm pulsed laser diode side-pumped acousto-optical (A-O) Q-switched Nd:YAG laser at repetition rates ranging from 10-100 kHz, producing a pulse train with a pulse number of 2-25. The maximum output energy of the oscillator is 15.6 mJ at 10 kHz, whereas it is 1.7 mJ at 100 kHz. After twostage amplifiers, a single-pulse energy of 85.2 mJ with a pulse-width of 14.5 ns is achieved at 10 kHz, which produces a peak power of 6.1 MW. At 100 kHz, the total burst energy reaches 220 mJ with a single-pulse energy of 8.8 mJ in the pulse burst laser system. [ABSTRACT FROM AUTHOR]

• A high pulse energy Nd:YAG laser is demonstrated and environmental tested. • Stable mechanical structure of resonator is designed and stress simulated. • Experimental proved high stability of output energy at different operation conditions. • Potentially benefits applications like PLIF and laser remote sensing. A high pulse energy laser diode-pumped Nd:YAG master oscillator power amplifier (MOPA) laser is demonstrated. The maximum energy of 68 mJ, 9.6 ns, 1064 nm laser at a pulse repetition frequency of 500 Hz is achieved by utilizing the amplifier composed of three LD side-pumped Nd:YAG modules. Moreover, the maximum laser energy of 35.6 mJ is obtained at 532 nm by employing a KTP crystal as a frequency doubler. When ambient temperature ranges from 5 °C to 45 °C, the master oscillator has a pulse energy jitter of <5%. During the shake-environment test, the maximum-pulse-energy jitter of the MOPA laser is less than 2%. The developed MOPA laser has been used in a laser-induced fluorescence system and the variation of the flow field is obtained at a repetition rate of 500 Hz. [ABSTRACT FROM AUTHOR]

The ultrafast molecular vibrational dynamics in PMMA sheets is studied by femtosecond time-resolved coherent anti-Stokes Raman spectroscopy at room temperature. The - stretch modes at 2870 cm-1 and 3008 cm-1 in PMMA sheets are excited and detected. The coherence relaxation times and beat wavenumbers of the Raman modes are obtained. [ABSTRACT FROM AUTHOR]

This paper reported a comparative study of molecular vibrational dynamics in different organic molecules by femtosecond time-resolved folded box-coherent anti-Stokes Raman scattering (TR-box-CARS) spectroscopy. As model system methanol and ethanol molecules are chosen, the coherence transfer between stretching vibration modes of C-H bonds in them are excited and detected at the same time. Different vibration periods and wavenumber spacing are found for the amplitudes of the coherent vibrations of C-H stretch modes in methanol and ethanol molecules. This study makes femtosecond TR-box-CARS possible as a prospective technique for detection and identification of organic molecular species in ambient environments. A simple spatial magic filter and frequency domain filter method with folded TR-box-CARS approach of suppressing the non-resonant FWM background is demonstrated. • A simple spatial magic filter and frequency domain filter method with folded TR-box-CARS approach of suppressing the non-resonant FWM background is demonstrated. • The coherent Raman modes of C-H stretch modes in different molecules were excited selectively and investigated simultaneously without tuning the laser frequencies due to the large spectral of the preparation pulses. • The obtained oscillations periods of the excited Raman modes, the wavenumber difference, and the decay times for the amplitudes of the Raman modes of C-H stretching vibrations are discussed and simply compared. • This work makes femtosecond TR-box-CARS spectroscopy possible as a prospective technique for detection and identification of organic molecular species in ambient environments by monitoring the coherent Raman modes of C-H bonds in different organic molecules. [ABSTRACT FROM AUTHOR]

Abstract: The effects of thermal treatment on infrared optical properties of SiO2 films on Si substrates by ion beam sputtering technology were investigated. Complex refractive index of SiO2 films was calculated from Fourier transform infrared transmission spectrum from 400 to 4000cm−1. Absorption band properties associated with Si-O-Si stretching, bending, rocking mode at about 1080cm−1, 816cm−1, 460cm−1 were analyzed. With the increase of thermal annealing temperature, the absorption peak with Si-O-Si stretching, rocking mode shift to long wave number, but the bending mode shifts to short. After thermal treatment, the infrared optical constants are close to the value of the more stabilized thermal grown SiO2. So, it can be concluded that the structure of Si-O-Si network in SiO2 films deposited on Si was modified to the stable structure of thermal grown SiO2. [Copyright &y& Elsevier]

[Display omitted] • A hybrid nonmetallic dye-lanthanide triplet sensitizer was demonstrated. • Lanthanide enhances spin-triplet intersystem crossing in dye molecules. • Energy migration among lanthanides enhances upconversion by up to 1740-fold. • Triplet fusion upconversion in solids remains stable over 12 h in air. Triplet fusion upconversion is useful for a broad spectrum of applications ranging from solar cells, photoredox catalysis, to biophotonics applications, especially in the near-infrared (NIR, >700 nm) range. This upconverting system typically demands efficient conversion of spin-singlet harvested energy through intersystem crossing to spin-triplet states, accessible only in rare metallic-coordinating macrocycle compounds or heavy-metal-containing semiconductor quantum dots for triplet sensitization. Herein, we describe an organic–inorganic system for NIR-to-visible triplet fusion upconversion, interfacing commonly-seen, non-metallic, infrared dyes (IR806, IR780, indyocynine green, and CarCl) and lanthanide nanocrystal (sodium ytterbium fluoride) as a hybrid molecular sensitizer, which extracts molecular spin-singlet energy to nanocrystal-enriched ytterbium dopants at ~48% efficiency (IR806, photoexciation at 808 nm). Moreover, ytterbium sub-lattice energy migration increases the interaction possibility between the nanocrystal and the freely-diffusing rubrenes in solution, resulting in 24-fold (IR806) to 1740-fold (indocyanine green) upconversion (600 nm) increase, depending on the IR dye type, as compared to the one without ytterbium nanotransducers. Ab initio quantum chemistry calculations identify enhanced spin-orbital coupling in the ytterbium-IR806 complex and high energy transfer rate in the ytterbium-rubrene interaction (1010 s−1). Employing inorganic lanthanide nanocrystals as nanotransducers unleashes the potential use of non-metallic infrared organic dyes for triplet fusion upconversion. [ABSTRACT FROM AUTHOR]

Abstract: Rational control over the uniform morphology and size of hexagonal NaYF4 has been achieved via a facile hydrothermal route. The evolution of particle morphology from peg-top-like to hexagonal microprisms with protruding centers and the long tubelike morphology with concave wedge and finally to solely microrods been demonstrated by increasing the F−/Ln3+ molar ratio, all other parameters being equal. Rationally controlling the shape of hexagonal NaYF4 is of great importance due to their strongly shape-dependent optical properties. Moreover, the systematic study on the photoluminescence of 20%Yb3+, 1%Er3+-doped β-NaYF4 with different shapes shows that the upconversion (UC) properties of these products are strongly dependent on the combined roles of morphologies, crystallinity, and particle sizes. In particular, the microrods evince a better PL signal as compared with others. [Copyright &y& Elsevier]

• Single-photon echo signals removed diffusion phenomenon in MCP-based image sensors. • Weighting algorithm and sub-pixel method processed single-photon echo signals. • The diffusion phenomenon was removed to reconstruct a high-resolution target image. • Laser active imaging quality improved in a high electronic gain environment. Image sensors based on microchannel plates (MCPs) have important applications as array image sensors owing to their high sensitivity and wide field of view, and because no scanning is required. When MCP-based image sensors, such as ICCD and ICMOS, are used for laser-active imaging, severe diffusion phenomenon occurs due to high electronic gain, and this significantly affects the resulting image quality. This study uses single-photon echo signals to remove the diffusion phenomenon in MCP-based image sensors. A laser-active imaging system based on a MCP image sensor produces single-photon echo signals of the target. The single-photon echo signals are then processed using a weighting algorithm and sub-pixel method, which effectively remove the diffusion phenomenon and reconstruct a high-resolution image of the target. Therefore, when the MCP-based image sensor operates in a high-electronic-gain environment, this method improves the quality of laser-active imaging. The study shows that the method can improve the image resolution obtained by a MCP-based image sensor to 25.51 lp/mm in high-electronic-gain conditions. [ABSTRACT FROM AUTHOR]

• A MOPA laser system with high pulse energy and sub-nanosecond pulse width was presented. • The thermal effect in LD-side-pumped modules was studied numerically and experimentally. • Pulses with high timing stability and good amplitude stability were obtained. A high-pulse-energy, sub-nanosecond master oscillator power amplifier (MOPA) laser system at 1.06 μm was demonstrated. The thermal effect in laser diode-side-pumped module was studied numerically and experimentally. The master oscillator was an electro-optically Q-switched laser with a pulse width of ~730 ps. Using an end-pumped preamplifier and two-stage side-pumped amplifiers, laser pulses with a pulse energy of 47.1 mJ were obtained at a repetition rate of 500 Hz, corresponding to a peak power of ~64.5 MW. The coefficient of variation of the pulse train was ~4.9%. [ABSTRACT FROM AUTHOR]

A 500 kHz burst-mode YVO 4 /Nd:YVO 4 1064 nm laser oscillator with a burst duration of 1 ms and a burst energy of 45.0 mJ was presented. The acousto-optically Q-switched frequency could be varied from 10 kHz to 500 kHz, resulting in 10–500 sub-pulses per burst. At the pulse repetition rate of 500 kHz, the maximum single pulse energy reached 90.0 μJ with a pulse width of 37.8 ns, corresponding to a peak power of 2.4 kW. The beam quality factor of burst-mode laser at 500 kHz was measured to be M2=1.6. The burst-mode YVO 4 /Nd:YVO 4 laser could be acted as a master oscillator for further power scaling. [ABSTRACT FROM AUTHOR]

Abstract: Solid-state dye laser materials based on polymethyl methacrylate (PMMA) doped with different concentrations of Coumarin 540A were prepared. The absorption, fluorescence and blue-green lasing spectra of the samples were obtained and studied in this latter. With the third harmonic generation (THG) of Q-switched Nd:YAG laser pumping the samples longitudinally, the highest slope efficiency is 12.8%, which is achieved in the sample with a dye concentration of 1.0×10−3 mol/L. [Copyright &y& Elsevier]