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At present, most researchers focus on plane wave incident on targets, but in practical applications, most of the beams are Gaussian beam. We study the scattering fields of Gaussian beam incident on rough cylinders. Coherent and incoherent scattering coefficients are obtained based on the angular spectrum expansion and physical optics approximation, and the effects of cylinder roughness, beam radius, cylinder radius and angle of incidence on scattering coefficients are analyzed. The results show that, for a constant wavelength, when the root mean square height is greater than or equal to 1/5 of the wavelength, the coherent scattering coefficient curve undergoes a change in its distribution, with the peak transforming into a trough. Furthermore, when the root mean square height is greater than or equal to 1/3 of the wavelength, the incoherent scattering coefficient experiences a decline as the root mean square height increases. The correlation length only affects the incoherent scattering coefficient. Both the coherent and incoherent scattering coefficients decrease with the increase in the incident angle. Finally, when the roughness and incident angle are constant, with the increase in the ratio of the cylinder radius to the beam waist radius, the scattered light field is more concentrated. Our results provide the theoretical basis for the measurement of the cylindrical scattering field.

Taking a comprehensive consideration of related excited state absorption, upconversion emission, and cross relaxation processes, a theoretical model concerning a pulsed Yb-Tm fiber laser is established. The criterion for stable Q-switching is derived with both excited state absorption processes and mode field area mismatch taken into account. And, detailed population transitions of major energy levels are illustrated. Impacts of pump power, mode field area ratio and saturable absorber length on the output characteristics of the pulsed laser system are investigated and analyzed. Simulations show that the excited state absorption transition 3F4→3F2,3 is the predominant factor supporting the passive Q-switching of Yb-Tm fiber lasers. Besides the pump power, the mode field area ratio and the length of the saturable absorber are also important factors affecting the output characteristics of the pulsed laser system. Proper choice of these parameters not only brings significant improvements to the pulse performance, with regards to both the pulse energy and the pulse duration, but also expands the stable operation range of the laser system. And, in practice, an effective mode field area ratio bigger than 1.65 should be exploited for the stable Q-switching operation of a pulsed Yb-Tm fiber laser.

Partial discharge (PD) is not only the main cause of insulation fault for power equipment, but also an important sign of insulation defects. Using the PD detection system based on ultra-high frequency (UHF) antenna array, the PD localization can be realized in air-insulation substation. At present, the methods commonly used in PD detection system localization include time difference of arrival (TDOA) method and spatial spectrum estimation (SSE) method. This paper introduced the principles of these two methods, and proposed a simulation system for PD direction finding. Using this system, the direction finding performance of the TDOA method and the SSE method under different signal-to-noise ratio, incident azimuth angle, rising edge time and array element spacing are compared. The conclusion shows that when the SNR is less than 0 dB or the element spacing is less than 0.23 m, the SSE system has better direction finding performance. When the element spacing is greater than 0.23 m, the SSE system will be fuzzy in direction finding. At this time, the TDOA algorithm can achieve higher direction finding accuracy.

We present a narrow linewidth frequency-doubled Cr:LiSAF laser with a 450- to 460-nm tunability and maximum repetition frequency (RF) of 63 kHz. Under a pump power of ∼900 mW, the fundamental wavelength could be tuned at the range of 883 to 1020 nm, with a maximum output power of 180 mW at 910 nm. The pulsed operation was achieved by using an acousto-optical modulator. An LBO crystal was adopted for intra-cavity frequency doubling and a maximum output power of 44.8 mW was obtained at 455 nm, indicating a slope efficiency of 11.2%. The spectral linewidth was

Background Solitary fibrous tumors are rare tumors derived from the pleura. A tumor generally has only one pedicle. Video-assisted thoracoscopic surgery is generally used when a tumor is small ( 10 cm). The larger specimen can be extracted from the smaller incision by the “pulling carrot” method.

We report, as far as we know for the first time, on a pulsed 2.7 µm Er:ZBLAN fiber laser Q -switched by an electro-optic modulator. The Q -switched operation was achieved with a repetition rate range of 100 Hz–50 kHz. Pulse energy of 205.7 µJ and pulse width down to 13.1 ns, yielding a peak power of 15.7 kW, were obtained at a repetition rate of 100 Hz. The linewidth of the output spectrum was as narrow as 0.4 nm. The pulse width and the pulse peak power, to the best of our knowledge, are currently the shortest and the highest in the 3-µm-band Q -switched fiber lasers, respectively.

Single-shot laser-induced damage threshold (LIDT) measurements of multi-type free-standing ultrathin foils were performed in a vacuum environment for 800 nm laser pulses with durations τ ranging from 50 fs to 200 ps. The results show that the laser damage threshold fluences (DTFs) of the ultrathin foils are significantly lower than those of corresponding bulk materials. Wide band gap dielectric targets such as SiN and formvar have larger DTFs than semiconductive and conductive targets by 1–3 orders of magnitude depending on the pulse duration. The damage mechanisms for different types of targets are studied. Based on the measurement, the constrain of the LIDTs on the laser contrast is discussed.

Impacts of Tm ion concentration and Ho ion concentration on the saturable behaviors of Tm-Ho codoped fiber saturable absorbers and the output characteristics of the passively Q-switched laser systems are investigated and analyzed both at the initial lasing state and the stable passive Q-switching state. Simulations show that, varying concentrations of Tm and Ho ions have different impacts on the temporal evolution processes but similar effects on the macroscopic characteristics of the laser system. The root for the impacts of dopant concentrations is the population of the 3H6 energy level and the cavity loss it induces. For Tm ions, the rise of the Tm concentration improves the population of the 3H6 energy level directly, while, for Ho ions, higher Ho concentration leads to larger recovery rate of the 3H6 energy level, thus increasing the population of the 3H6 energy level indirectly. As for limited total dopant concentration, the Tm:Ho concentration ratio can be optimized for different applications.

Simple Summary Commercial breeder farms are moving forward using colony cages due to high efficiency, low energy input, clean production, and as a result of the rising public concerns with respect to the welfare of hens in conventional cages. Compared with conventional cages, layer breeders in colony cage are the parent-stock of laying hens and are confined together with roosters. However, the use of colony cages is still in a preliminary stage due to behavioral issues such as feather pecking (FP) and cannibalism. These behaviors can cause poor health, poor welfare, and economic problems. It is necessary to identify effective and proximal management practices to alleviate the damage that is caused by FP and cannibalism in such colony cage systems. This study aims to mitigate the problems of FP and cannibalism by utilizing light environment regulation. Results of this study indicates that red light and low light intensity could effectively alleviate FP and cannibalism during the laying period. Such knowledge might help to understand FP behavior and stress susceptibility of hens in this system and will provide a basis for the optimization of the cage equipment and the regulation of light environment. Abstract Natural mating colony cages for layer breeders have become commonplace for layer breeders in China. However, feather pecking (FP) and cannibalism are prominent in this system. The objective of this study was to investigate the effects of four light-emitting diode (LED) light colors (white: WL, red: RL, yellow-orange: YO, blue-green: BG) with two light intensities for each color, on FP, plumage condition, cannibalism, fear, and stress. A total of 32 identical cages were used for the eight treatments (four replicates for each treatment). For both light intensities, hens in RL had a lowest frequency of severe FP, whereas hens in WL had the highest frequency of severe FP. Hens in RL and BG had better plumage conditions than in WL and YO. Compared with RL and BG treatments, hens treated with WL and YO had a significantly longer tonic immobility (TI) duration. Hens treated with RL had a higher concentration of 5-hydroxytryptamine (5-HT), a lower concentration of corticosterone (CORT), and a lower heterophil to lymphocyte ratio than WL and YO. Furthermore, RL could significantly reduce mortality from cannibalism. Overall, hens treated with RL and low light intensity showed a lower frequency of severe FP, less damaged plumage, were less fearful, had lower physiological indicators of stress, and had reduced mortality from cannibalism. Transforming the light color to red or dimming the light could be regarded as an effective method to reduce the risk of FP and alleviate the fear responses of layer breeders.

To increase the lifetime of components in high power lasers and to study downstream light field the influence of the damaged optical components, numerical model of surface profile of damaged optical components were built with particle swarm optimization algorithm, and the relationship between the damage degree and the parameter of numerical model was analyzed. First laser irradiation experiment was carried out to acquire the damaged optical components. Then surface morphology was measured with Zygo interferometer system. With a typical Gaussian filter. A numerical model of one dimensional lineout of surface profile was established with particle swarm optimization algorithm. Numerical results shows that the model was valid with the particle swarm optimization (PSO) algorithm. The results also shows that there was a relationship between parameter of the model and the damage degree.

A theoretical model concerning FSA-based active Q-switching is developed. And, characteristics of the active Q-switching operation are investigated and compared with the traditional passive Q-switching operation. Numerical results demonstrate that the active control of the repetition rate of FSA-based Q-switching is attainable. And, stable active Q-switching could be obtained from both no lasing state and stable passive Q-switching state.

We build a Tm-doped fiber amplifier based on a gain-switched seed laser. At Er-doped fiber-laser pumping, the maximum peak power of the gain-switched seed pulse is 227.7 W with a pulse duration of 48.3 ns. In the amplifier, peak power of the amplified pulse reaches 1.1 kW with a 3 dB linewidth of 0.06 nm. Supercontinuum generation is observed when this amplified pulsed laser source is injected into a section of 7 m long Tm-doped double-clad fiber.

We present an all-fiber 1150 nm Yb-doped fiber laser oscillator pumped by a 976 nm laser diode. To suppress amplified spontaneous emission and avoid parasitic laser oscillation, we propose a long-length gain fiber and a high-reflectivity output fiber Bragg grating in the fiber laser oscillator. The 1150 nm band single-mode fiber laser with output power of 20.5 W is demonstrated at room temperature. The optical-to-optical conversion efficiency ranges up to 51.6% at the maximum output. The central wavelength of the fiber laser oscillator is 1150.35 nm, and its 3 dB spectral width is 0.72 nm. No evidence of amplified spontaneous emission, residual pump light, or parasitic laser oscillation were observed in the experiments. The high-power 1150 nm fiber laser oscillator can be used as a pump source in the development of a 3 μm Ho-doped fiber laser.

With both radiation effects and thermal effects taken into consideration, a multiphysics thermal model concerning high-power Yb-doped fiber lasers operated with post-irradiated active fibers is established. Radiation-related parameters, including propagation losses, refractive indexes and lifetime, are considered. And, with the temperature profile of the active fiber, temperature-dependent parameters, including absorption and emission cross-sections, refractive indexes and lifetime, are updated every loop to simulate the output parameters. Simulation results show that radiation induces great changes to the thermal profiles of the active fiber. And severe performance degradation of high-power Yb-doped fiber lasers are recorded, featuring a remarkable drop in output power and an even steeper decline in the transverse mode instability threshold, which is a predominant limitation at high radiation doses. With a deposited radiation of 100 Gy, an output decline of about 50% and a mode instability threshold drop over 85% are observed. And it’s shown that, with the exploited active fiber, it’s hardly possible for the investigated fiber laser to generate stable single-mode output at kilowatt levels with accumulated radiation doses beyond 50 Gy. At low radiation doses within 20 Gy, to maintain safe and stable single-mode operation of the laser system, longer active fibers with lower absorption coefficients are preferred despite a small rollover of the output power.

We build an all-optical, all-fiber actively Q-switched Er-doped fiber laser with a simple ring cavity. Active Q-switching is attained by saturating a section of 34 cm Tm–Ho co-doped fiber saturable absorber with a 1550 nm pulsed fiber laser. The repetition rate of the pulsed output is 30 kHz determined by that of the subsidiary pump. The maximum pulse energy generated is about 80 nJ with a pulse duration of 2.07 μs. The line width of the pulsed output is only 0.054 nm limited by the resolution capability of the spectrum analyzer.

Besides the excessive saturation effect, a new mechanism of temporary black screen of CCD camera induced by laser is found. The final output of CCD camera is the difference between the signals in effective pixels and optical black pixels. As the effective pixels of CCD camera are being irradiated by intense laser, many carriers induced by photo overflow from effective pixels into the optical black pixels. As a result, both the effective and optical black pixels will reach saturation, which makes the final output of CCD become zero. This effect has the same black screen phenomenon as the excessive saturation, and is named as pseudo-excessive saturation effect in this article.

Three types of laser irradiating experiments on single junction GaAs solar cells with the same laser energy coupling intensity were carried out, which were irradiated by in-band (808 nm) and out-of-band (1.07 μm) continuous wave lasers respectively and simultaneously. On the basis of the changes of current-voltage characteristic curves of irradiated solar cells, the damage degrees could be divided into three stages which were gently, seriously and thoroughly damaged stages. The damage mechanism was studied from two aspects: output changes of solar cell equivalent circuit under different configuration settings, thermal analysis model. The results show that damage degrees of gently and thoroughly damaged stages is insensitive to irradiation intensity. However, the damage degree of seriously damaged stage is sensitive to irradiation intensity and this is regarded to be related to thermal decomposition of GaAs. Moreover, the increase of PN junction defects leads to performance degradation of irradiated solar cells. In conclusion, the thermal damage leads to the increase of PN junction defects, thus results in the performance degradation of cells.

Optical components in large aperture optical imaging system are susceptive to intense laser radiation. Optical band pass filter for spectra selection and nonlinear filter for intense laser blocking, are usually focal or near focal elements in imaging system, will more likely to be permanently damaged by high intense unwanted laser irradiating. In order to relate the optical imaging performance degradation to laser irradiating parameters, characteristics of the damage sites and so on, a test facility consisting of scaled electro-optical imaging system and standard imager evaluation system was constructed, and the linear spread function, modulation transfer function, signal transfer function, and noise power spectrum were obtained. Experimental imaging performance degradation law of damaged fused silica and colored glass filters were analyzed. Furthermore, some brief discussions on the imaging performance degradation mechanisms are also presented.

A theoretical model concerning the 3 H 6 → 3 F 4 transition of Tm ions for passive Q-switching of an Er-doped fiber laser is built. Related population transitions of the passive Q-switching mechanism are simulated and described. Effects of pump power, output reflectivity and cavity length on the laser performance are investigated and analyzed. Numerical results indicate that pump power and output reflectivity are major factors affecting the laser output, while the cavity length mainly determines the pulse duration. Besides, high repetition rate operation is achievable with 3 H 6 → 3 F 4 transition of Tm ions at the expense of the output pulse energy.

Natural mating colony cages for parent-stock layer breeders, instead of conventional cages with artificial insemination, have been widely adopted by many commercial farms in China. Although some natural mating behaviours can be expressed and broader activity space is provided compared with that of conventional artificial insemination cages, the environment is still relatively barren. The aim of this study was to investigate the effects of providing nest boxes and claw abrasive devices (CADs) in this colony cage system on feather pecking (FP), feather condition, fear and physiological stress in layer breeders. Twelve treatments were compared in a factorial arrangement, including 2 types of nests (large and small), 3 types of CADs (abrasive strips, rubber mat with grooves, and metal plates with holes), and the control (without the provision of nests and CADs). Nine cages per treatment were involved, with 10 roosters and 90 hens per cage. The results showed that the nests had a significant effect (P ≤ 0.05) on the frequency of severe feather pecking (SFP); environmental pecking (ENP); food pecking (FOP); back, rump, and belly coverage condition; tonic immobility (TI) duration; avoidance distance (AD); and corticosterone and 5-HT concentrations. Except for the blood parameters, the CADs had a significant effect (P ≤ 0.05) on the frequency of SFP and FOP; back, rump, tail coverage condition; duration and latency of TI test; hens’ novel object (NO) recognition score; and distance in the AD test. In addition, significant nest × CAD interactions (P ≤ 0.05) were noted for SFP, ENP, and FOP; back, rump, and tail coverage condition; duration in the TI test; hens’ novel object (NO) recognition score; distance in the AD test; and the concentration of corticosterone. Mortality was significantly (P ≤ 0.05) reduced by nests, CADs and their interaction. It was concluded that the nests and CADs that were equipped in our study could be regarded as rewarding environmental necessities that could alleviate FP activities, improve feather coverage condition, and reduce stress levels and mortality rates. Large nests and abrasive strips were the preferred choice over colony cages without nests and CADs.

Considering the two most important factors, delamination and tensile strength temperature dependence, a tensile strength prediction model for orthogonal carbon fiber reinforced polymer (CFRP) under continuous wave (CW) laser irradiation is proposed. In the prediction model, delamination was judged by the thermal data recorded by a thermal imager. In order to eliminate the influence of heating rate on the tensile strength temperature dependence parameters, a two-sided laser irradiation method was proposed to test the tensile strength temperature dependence of CFRP. Furthermore, according to the temperature distribution in the thickness direction of the T700/E44 CFRP specimen and the tensile strength temperature dependence, the tensile strength for orthogonal CFRP under CW laser irradiation was calculated. The results show that the prediction model can reflect the decreasing process of tensile strength with laser irradiation, especially in the cases of high intensity laser irradiation and high tensile load. This research can make a reference for the tensile strength prediction of composite materials in high intensity CW laser irradiation and pre-tension loading conditions.

A diode-cladding pumped mid-infrared passively Q-switched Er3+-doped ZBLAN fiber laser with an average output power of watt-level based on a semiconductor saturable absorber mirror (SESAM) is demonstrated. Stable pulse train was produced at a slope efficiency of 17.8% with respect to launched pump power. The maximum average power of 1.01 W at a repetition rate of 146.3 kHz was achieved with a corresponding pulse energy of 6.9 μJ, from which the maximum peak power was calculated to be 21.9 W. To the best of our knowledge, the average power and the peak power are the highest in 3 μm region passively Q-switched fiber lasers. The influence of gain fiber length on the operation regime of the fiber laser has been investigated in detail.

Super-flat supercontinua are generated from a double clad Tm-doped fiber amplifier. Two different laser configurations are investigated and compared. In the direct-output configuration, the long-wavelength edge of the supercontinuum spectra is extended to beyond 2.65 μm with a 10 dB bandwidth of 740 nm. In the passive pigtail configuration, the generated supercontinuum features excellent flatness with an intensity difference smaller than 1 dB in the wide central spectral range from 1.98 μm to 2.41 μm.

A Tm–Ho codoped fiber amplifier system is built. And, amplification of a gain-switched Tm–Ho codoped fiber laser is investigated. Average output of 300 mW is obtained at repetition rate of tens of kHz with an amplification gain bigger than 11 dB. And, pulse amplification efficiency of resonantly pumped Tm–Ho codoped single clad fiber is comparable with 793 nm pumped Tm-doped double clad fiber. The maximal pulse energy generated is about 13.1 μJ, corresponding to a peak power of 282 W at 20 kHz. During the amplification process, gain-switching, partially modulated gain-switched mode-locking and 100% modulated gain-switched mode-locking are observed sequentially. At gain-switching mode, the laser output enjoys a narrow linewidth of 0.31 nm, while at gain-switched mode-locking mode, the spectral linewidth broadens to 0.6 nm.

The hyperspectral absorption spectroscopy is attracting more and more attention as this technique enables continuous wavelength sweep over a whole absorption band, rather than one or several discrete absorption lines. Owing to the H2O possesses much stronger and more abundant absorption lines in the 2μm region, this work develop a widely tunable, narrow linewidth Tm-doped fiber laser around 1.87μm for the application of combustion diagnostics. The laser wavelength tuning range is designed from 1850 nm to 1890 nm to overlap the strong absorption band of H2O, and the laser linewidth is further narrowed to 0.04 nm by a fiber saturable absorber. With this laser system, demonstration experiments are implemented for the continuous detection of H2O absorption lines. Detailed absorption peaks of H2O from 1866 nm to 1879 nm are detected and well-resolved. The measured absorption spectrum agree well with the theoretical computation derived from HITRAN2012 database quantitatively, verifying this laser system ready for hyperspectral absorption applications.

Two possible methods for repetition rate improvement of Tm-doped fiber saturable absorber based passively Q-switched Er-doped fiber lasers are reviewed. Simulations show that both methods are effective.

In this article, an overview of laser dazzling effect to buried channel CCD camera is given. The CCDs are sorted into staring and scanning types. The former includes the frame transfer and interline transfer types. The latter includes linear and time delay integration types. All CCDs must perform four primary tasks in generating an image, which are called charge generation, charge collection, charge transfer and charge measurement. In camera, the lenses are needed to input the optical signal to the CCD sensors, in which the techniques for erasing stray light are used. And the electron circuits are needed to process the output signal of CCD, in which many electronic techniques are used. The dazzling effects are the conjunct result of light distribution distortion and charge distribution distortion, which respectively derive from the lens and the sensor. Strictly speaking, in lens, the light distribution is not distorted. In general, the lens are so well designed and fabricated that its stray light can be neglected. But the laser is of much enough intensity to make its stray light obvious. In CCD image sensors, laser can induce a so large electrons generation. Charges transfer inefficiency and charges blooming will cause the distortion of the charge distribution. Commonly, the largest signal outputted from CCD sensor is restricted by capability of the collection well of CCD, and can’t go beyond the dynamic range for the subsequent electron circuits maintaining normal work. So the signal is not distorted in the post-processing circuits. But some techniques in the circuit can make some dazzling effects present different phenomenon in final image.

A pulsed Er 3+ -doped ZBLAN fiber laser at 2.8 μm in fundamental-transverse-mode operation is reported. Stable gainswitching is achieved with the repetition rate range from 0.5 to 10 kHz. The maximum laser pulse energy of up to 4.2 μJ and pulse duration of 1.18 μs at a repetition rate of 10 kHz, yielding the maximum peak power of 3.5 W, has been obtained. The maximum slope efficiency with respect to the launched pump power at 975 nm is determined to be 12.2%. Pulse spikes occur by increasing the pump energy of larger than 75 μJ.

The design and performance of a closed cycle, repetitively pulsed HF/DF laser is described. For obtained higher stable laser pulse energy and running frequency, discharge stability with different electrode profile and different gas circulation structure are researched. The functional relations of laser pulse energy with electric field strength (E) and gas mixture pressure (P) for various gas flow velocity are studied. It is shown that with preliminary optimized of the gas injection segment structure before pump region and optimal E/P conditions, maximal running frequency of 100Hz is obtained and operating stability keeps well. Under these conditions, the laser average power is 40W and peak power is 4MW.