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We report on the frequency expansion of efficient passively Q-switched (PQS) orthogonally-polarized dual-wavelength laser for the first time, to our knowledge. The dynamic of pulse synchronization for the PQS dual-wavelength laser was analyzed theoretically. With two Nd:YLF crystals, the simultaneous PQS orthogonally-polarized dual-wavelength laser at 1047 and 1053 nm was obtained with the maximum output powers of 4.5 and 4.2 W, respectively, resulting in a total optical-to-optical conversion efficiency of 18.7%. The timing jitter between the 1047 nm main pulse and 1053 nm main pulse was 26.6 ns. Furthermore, substituting one of the Nd:YLF crystals for a Nd:YAG crystal, two sets of simultaneous orthogonally-polarized dual-wavelength lasers at 1047, 1064 nm and 1053, 1064 nm were generated with near 6 W of output power.

We demonstrate both experimentally and numerically a new type of hole array structure that exhibits optically diffractive focusing phenomenon. The hole arrays are designed based on the aperiodic Vogel spirals. In contrast to periodic and quasi-periodic hole arrays that contain discrete Bragg peaks in reciprocal space, the Vogel spiral hole arrays have particularly continuous Fourier components with circular symmetry, which enables optical wave focusing into a diffraction-limited hotspot for a wide range of incident wavelengths. We further demonstrate that the diffracted fields contain local orbital angular momentum (OAM) leading to rotations of the diffractive circular rings around the center, although the total OAM is zero.

We report a high average power actively Q-switched (AQS) orthogonal polarization dual-wavelength Nd:YLF laser at 1047 and 1053 nm. The gain-to-loss balance of dual wavelengths was realized via an uncoated quartz etalon. A maximum continuous wave (CW) output power of 14.2 W was obtained under the incident pump power of 41.7 W, corresponding to an optical-to-optical conversion efficiency of 34.1% and a slope efficiency of 38.3%. Active Q-switching was accomplished by inserting an acousto-optic modulator in the cavity. Under the incident pump power of 40 W, this setup delivered a maximum average output power of 10 W at the pulse repetition frequency (PRF) of 30 kHz and the largest pulse energy of 3.4 mJ at the PRF of 1 kHz, respectively. To the best of our knowledge, these are the highest average output powers for both CW and AQS orthogonally polarized dual-wavelength lasers based on laser crystals.

This study investigated the feasibility of using fluorescence hyperspectral imaging technology to diagnose of early-stage gastric cancer. Fluorescence spectral images of 76 patients who were pathologically diagnosed as non-atrophic gastritis, premalignant lesions and gastric cancer were collected. Fluorescence spectra at 100-pixel points were randomly extracted after binarization. Diagnostic models of non-atrophic gastritis, premalignant lesions and gastric cancer were constructed through partial-least-square discriminant analysis (PLS-DA) and support vector machine (SVM) algorithms. The prediction effects of PLS-DA and SVM models were compared. Results showed that the average spectra of normal, precancerous and gastric cancer tissues significantly differed at 496, 546, 640 and 670 nm, and regular changes in fluorescence intensity at 546 nm were in the following order: normal > precancerous lesions > gastric cancer. Additionally, the effect of the diagnostic model established by SVM is significantly better than PLS-DA which accuracy, specificity and sensitivity are above 94%. Experimental results revealed that the fast diagnostic model of early gastric cancer by combining fluorescence hyperspectral imaging technology and improved SVM was effective and feasible, thereby providing an accurate and rapid method for diagnosing early-stage gastric cancer.

We demonstrate that the spatially diffractive properties of cylindrical vector beams could be controlled via linear interactions with anisotropic crystals. It is the first time to show experimentally that the diffraction of the vector beams can be either suppressed or enhanced significantly during propagation, depending on the sign of anisotropy. Importantly, it is also possible to create a linear non-spreading and shape-preserving vector beam, by vanishing its diffraction during propagation via strong anisotropy in a crystal. The manageable diffractive effect enables manipulating propagation dynamics of the circular Airy vector beams, i.e., their propagation trajectories can be dynamically controlled by weakening or enhancing self-acceleration of the Airy beam. We further demonstrate that the cylindrical vector beams with initially zero orbital angular momentum can be rotated either clockwise or anticlockwise, relying on the sign of the anisotropy.

The use of Yb

We observe a nonlinear response of a dual-wavelength Nd:YAG laser when subjected to low-frequency periodic modulations of cavity losses. The modulation frequency is far from the relaxation oscillation frequency. The harmonic resonances of the two laser wavelengths associated with antiphase intensity oscillations are demonstrated and resonances up to the fourth order were observed. For relatively weak modulation, the intensity oscillation frequency of the laser is equal to the modulation frequency. Harmonic resonances occur under a stronger modulation. We find that more harmonic components appear when the modulation frequency is increased. Furthermore, with enhancing the modulation, the dominant frequency of the intensity oscillations of both wavelengths is shifted toward the higher-order harmonic frequency.

In this paper, [NaGd1-xNdx](MoO4)2 crystals with x = 0.005–0.05 were grown by Czochralski method at 950 ℃ for 10 hours and subsequently characterized by absorption spectroscopy and fluorescence spectroscopy. The intensity parameters of Nd3+ were calculated by Judd-Ofelt theory, and the relationship between the parameters and Nd3+ concentration was analyzed. The results show that with the increasing Nd3+ concentration, the oscillator strength, stimulated emission cross-section, Ωt and spontaneous transition probability decrease slightly, while the fluorescence lifetime decreases significantly. However, the fluorescence branching ratio is almost unchanged with the increasing Nd3+concentration. The [NaGd1-xNdx](MoO4)2 crystal with (x = 0.01) possesses the highest quantum efficiency of 88.98%, a good fluorescence line-width of 23 nm, a large value of σem·τf up to 0.55 × 10−22 cm2·s and a stimulated emission cross-section up to 3.747 × 10−19 cm2 for the transition from 4F3/2 to4I11/2 at 1064 nm. Test results indicate that [NaGd1-xNdx](MoO4)2 crystals are an excellent gain media for the solid state laser system.

BACKGROUND Vibrio parahaemolyticus is the leading causative pathogen of gastroenteritis often related to contaminated seafood. Photodynamic inactivation has been recently proposed as a strategy for killing cells and viruses. The objective of this study was to verify the bactericidal effects caused by photodynamic inactivation using methylene blue (MB) over V. parahaemolyticus via flow cytometry, agarose gel electrophoresis and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Vibrio parahaemolyticus counts were determined using the most probable number method. A scanning electron microscope and a transmission electron microscope were employed to intuitively analyze internal and external cell structure. RESULTS Combination of MB and laser treatment significantly inhibited the growth of V. parahaemolyticus. The inactivation rate of V. parahaemolyticus was >99.99% and its counts were reduced by 5 log10 in the presence of 0.05 mg mL−1 MB when illuminated with visible light (power density 200 mW cm−2) for 25 min. All inactivated cells showed morphological changes, leakage of cytoplasm and degradation of protein and DNA. CONCLUSION Results from this study indicated that photodynamic technology using MB produced significant inactivation of V. parahaemolyticus mainly brought about by the degradation of protein and DNA. © 2015 Society of Chemical Industry

We study theoretically and experimentally pulse fluctuations in a passively Q-switched laser caused by the thermal lens effect and design a special thermally insensitive cavity for an end-pumped passively Qswitched laser system with a composite crystal. We show experimentally that using a suitable cavity and maintaining the laser-system operation in the fundamental mode reduce the pulse fluctuations effectively. Under a pump power of 8 W, relative fluctuations of the pulse width and the repetition rate of this system are 2.3% and 3.5%, respectively.

We experimentally demonstrated, the first time to the best of our knowledge, the intracavity Stokes frequency conversion using a Yb:YAG crystal as gain medium and a YVO4 as Raman crystal. At an incident pump power of 9.72 W and a pulse repetition frequency of 39 kHz, the first-Stokes emission at 1157.6 nm with a spectral linewidth of 2.2 nm was observed with respect to the Raman shift of 890 cm $^{-1}$ . The maximum pulse average output power of 750 mW at 1157.6 nm was achieved, with a corresponding incident pump beam to first-Stokes output conversion efficiency of 7.72%.

In order to improve feed safety, we investigated the feasibility of using fluorescence spectral imaging (FSI) technique to qualitatively detect meat and bone meal (MBM) mixed with fish meal (FM). Using the FSI system, the spectra of 90 FM and MBM samples from different regions were collected with denoising and binary processing to obtain images. The spectral data curves over the wavelength range of 400–680 nm were used for identification and were pre-treated with various methods. Next, the curves were plotted based on stereo spectrograms; then, partial least squares discriminant analysis (PLS-DA) was applied to determine the FM and MBM samples. One FM sample and one MBM sample were randomly selected and mixed together (v/v, 1:1), and the mixture’s pseudo-color (PC) image was generated by mapping the best grayscale values using a spectrogram method. The resulting PC image was then used for spatial identification of the mixture. The PLS-DA results indicated that the identification effect was best after the multiplicative scatter correction where the sensitivity, specificity, and accuracy all equaled to 1. The PC image demonstrate that the FM (green) and MBM (red) accounted for 52.6 and 47.4 % of the total volume, respectively, corresponding with the actual 1:1 ratio. Additionally, the experimental test of three low concentration-mixed powder samples (c[MBM] = 1.5 %, c[MBM] = 3 %, and c[MBM] = 5 %) determined that the lower limit of application (LLA) of the proposed method is c[MBM] = 1.5 %. Theoretical limit of detection (LOD) of the method was calculated about c[MBM] = 0.75 % through linear regression. These experiments show that the spectral and spatial information provided by FSI can rapidly and nondestructively determine whether FM is mixed with MBM.

The use of Pr3+ codoping for enhancement of the 2.7 μm emissions was investigated in the Er/Yb codoped LiNbO3 crystal for the first time. The 2.7 μm emission characteristics and energy transfer were also investigated.

Well-crystallized and uniform NaGd(MoO4)2 microcrystals with morphologies of bipyramids, truncated bipyramids, quasi-cubes and tetragonal plates were selectively synthesized via a facile hydrothermal method without any additives under mild conditions. The effects of Na2MoO4/Gd(NO3)3 molar ratios and pH values of precursor solutions on the phase and morphology of the as-synthesized microcrystals were systematically investigated. The molar ratios and pH values played key roles in the selective synthesis of pure phase NaGd(MoO4)2 microcrystals with regular morphology. With increasing Na2MoO4/Gd(NO3)3 molar ratios in the appropriate pH range, the morphology of the products changed from bipyramids, truncated bipyramids, quasi-cubes to tetragonal plates, namely, the morphological truncation degree increased gradually. NaGd(MoO4)2 tetragonal microplates could be synthesized at the molar ratio of 9 : 1. A possible morphological formation mechanism of NaGd(MoO4)2 tetragonal microplates was proposed, i.e. nucleation-Ostwald ripening growth process. Color tunable photoluminescence properties of NaGd(MoO4)2:Eu3+,Tb3+ microcrystals were studied in detail. Among the different morphologies of NaGd(MoO4)2:5% Eu3+ microcrystals, tetragonal microplates had a broadened, red-shifted and enhanced charge transfer band in the excitation spectrum. What's more, the full-width at half-maximum for the charge transfer band of the tetragonal plates was highest (58 nm), which favored efficient excitation and absorption in the ultraviolet region. The introduction of a small amount of Tb3+ into NaGd(MoO4)2 microplates doped with Eu3+ would enhance the 5D0 → 7FJ transition of Eu3+ at 616 nm due to the energy transfer process of cross-relaxation from Tb3+ to Eu3+. Multicolor tunable luminescence from deep red, red, orange, yellow to green under 291 nm ultraviolet excitation and from red, reddish orange to pink under 380 nm near-ultraviolet excitation could be obtained in NaGd(MoO4)2 tetragonal microplates by simply adjusting the doping concentrations of Eu3+ and Tb3+, suggesting NaGd(MoO4)2:Eu3+,Tb3+ microcrystals might have practical application in optoelectronic devices, such as light emitting diodes and color display systems. This facile morphology-controlled hydrothermal synthesis strategy was simple, low-cost and environment-friendly, and might be extended to other inorganic materials.

Nd:YAG/KTA intra-cavity Raman lasers with two different Raman shifts are experimentally compared for eradiating around 1.15 µm. The different Raman processes are attributed to polarization dependent Raman gain of KTA crystal and nearly linear polarization of Nd:YAG fundamental light with Q-switch operation. Under an incident pump power of 10.2 W and a pulse repetition frequency of 15 kHz, 1.24 W output for the third-Stokes at 1150 nm in X(ZZ)X Raman configuration with the Raman shifts of 234 cm

The use of Nd

The experimental curriculum system is directly related to talent training quality. Based on the careful investigation of the developing request of the optoelectronic information talents in the new century, the experimental teaching goal and the content, the teaching goal was set to cultivate students' innovative consciousness, innovative thinking, creativity and problem solving ability. Through straightening out the correlation among the experimental teaching in the main courses, the whole structure design was phased out, as well as the hierarchical curriculum connotation. According to the ideas of "basic, comprehensive, applied and innovative", the construction of experimental teaching system called "triple-three" was put forward for the optoelectronic information experimental teaching practice.

We have experimentally demonstrated passively Q-switched (PQS) stimulated Raman scatting (SRS) emissions in an a-cut YVO

We propose a novel and efficient F

A Tm 3+ /Ho 3+ :NaGd(MoO 4 ) 2 crystal was grown by the Czochralski method. The XRD results matched standard data from JCPDS file, which accorded with scheelite structure with an I41/a space group. Thermal properties of crystal were analyzed by using the TG–DSC curve. The melting point and specific heat are 1182 °C and 0.5 J/g K at 300 K, respectively. The Spectral properties of the Tm 3+ /Ho 3+ :NaGd(MoO 4 ) 2 crystal were investigated, including room temperature absorption spectrum and fluorescence spectrum. The absorption cross-section of Tm 3+ at 796 nm is 4.33 × 10 −20 cm 2 with pertinent full widths at half maximum (FWHM) of 10 nm. The intensity parameters, spontaneous emission probability, fluorescence branching ratios and radiative lifetimes were calculated by Judd–Ofelt theory. The emission cross-sections are 1.47 × 10 −20 cm 2 and 1.36 × 10 −20 cm 2 for Tm 3+ at 1850 nm and Ho 3+ at 2000 nm respectively. The lifetime of 5 I 7 → 5 I 8 (Ho 3+ ) was 4.263 ms.

A stable and compact deep ultraviolet laser system operation at 266 nm with diode-side-pumped and passively Q-switched is reported. The Nd:YAG/Cr4+:YAG/YAG composite crystal is used in realizing fundamental laser output and passively Q-switched modulation and for achieving a high conversion efficiency from 532 nm to 266 nm; a multi-reflected cavity for 532 nm is used in the system. The performances of the average power, pulse width, and pulse repetition rate on pump power are measured. Under the green laser of 13.03 W, the deep ultraviolet laser average output power of 1.27 W is obtained, with a pulse width of 60 ns, the repetition rate of 12.5 kHz, and the corresponding conversion efficiency of 9.74%.

We experimentally investigated the performance of diode-wing-pumped Tm:Y 3 Al 5 O 12 crystalline laser operating at around 2 μm. By systematically making comparisons of laser performance in addition to the laser spectra features between composite and non-composite crystals with two different active segments length, we believed that using diffusion-bonded crystal with shorter Tm 3+ -doped active segment would be a feasible approach for simultaneously up-scaling the output power and slope efficiency in terms of reducing the reabsorption loss and thermal lensing effects.

A side-pumped passively Q-switched 1064 nm laser system by using Nd: YAG/Cr4+: YAG/YAG composite crystal is demonstrated for the first time. Under pump power of 180 W, the maximum average output power of 85.6 W is obtained, with the pulse width of 140 ns and the repetition rate of 14.3 kHz, corresponding single pulse energy of 6.0 mJ and peak power of 42.7 kW. To our knowledge, this is the maximum average power of 1064 nm passively Q-switched laser which has reported.

1.0 at% doped Nd3+:Gd0.1Y0.9AlO3 (Nd3+:GYAP) crystals with high optical quality were successfully grown by Czochralski (CZ) method. In this study, the Nd3+:GYAP crystal was firstly used for laser demonstration with an 808 nm laser diode (LD) to our best knowledge. Two lasers, emitted at 1078 nm and at 1341 nm, respectively, with a maximum power of 8.12 W and 2.36 W, were obtained under an absorbed power of 24.12 W and 15.22 W, respectively. The slope efficiencies of these two laser systems before saturable effect were experimentally determined to be 41% and 21%. Two lasers operated in linear polarization and no thermal depolarization was observed during the experiment, indicating that such Nd3+:GYAP based lasers possess good polarization performance.

An efficient enhancement and broadening 3 μm luminescence in the Er/Ho/Pr: PbF2 crystal was obtained for the first time. The 3 μm emission characteristics and energy transfer mechanism of the as-grown crystals were investigated in details. It shows that the introduced Er3+ ion can not only act as a sensitizer for Ho3+ ion to allow the crystal to be pumped by a 980 nm laser diode, but also broaden the 3 μm fluorescence emission. Moreover, the Pr3+ ions can also act as a suitable deactivated ion for Er3+ and Ho3+ ions, bringing about the enhancing of 3 μm fluorescence emission. These results suggest that the Er/Ho/Pr: PbF2 crystal may have potential applications around 3 μm broadband lasers.

We demonstrate an 806 nm laser diode end-pumped continuous-wave (CW) and actively Q-switched (AQS) orthogonally-polarized dual-wavelength Nd:YLF laser operating at 1314 and 1321 nm. Benefitting from the small difference of the stimulated emission cross sections at 1314 and 1321 nm in Nd:YLF crystal, the power equalized emissions at both wavelengths were achieved by simply titling the output coupler. A maximum CW output power of 9.2 W was obtained with the incident pump power of 32.5 W, giving an optical-to-optical conversion efficiency of approximately 28% and a slope efficiency of approximately 33%. Furthermore, active Q-switching was realized by inserting a Brewster-cut acousto optic modulator. For an incident pump power of 30 W, this oscillator delivered an average power of 6.5 W at a pulse repetition frequency (PRF) of 20 kHz, and a pulse energy of 2.6 mJ with a peak power of approximately 72 kW at a PRF of 1 kHz.

Here we investigated photo-darkening (PD) effect and its influence on laser performance in Yb3+-doped microstructure optical fiber made through the laser sintering technique (LST). Through measuring the temporal evolution of PD excess loss at 633 nm and fiber lasing characteristics, it was found that the home-made fiber has relatively low PD and high slope efficiency. The obtained PD equilibrium loss αeq at 633 nm is 1.07 dB/m. After 30 h 976 nm laser irradiation, the fiber presents a quite small power degradation of 0.45 %. Moreover, the laser slope efficiency shows a small decline of 0.26 %, from 81.03 % to 80.77 %. The investigation of optical performance demonstrates that Yb3+-doped fiber fabricated by LST has uniform elements distribution, reasonable absorption, low background loss and a relatively low PD behavior, making it a potential application for effective high-power fiber lasers.

The Tm,Ho:Lu2O3 crystal was grown by the optical floating zone method for the first time. The XRD pattern shows that it belongs to the cubic crystal system (Ia‾3 space group). The absorption cross-section at 796 nm is 4.21 × 10 − 21 cm2, the full width at half maximum (FWHM) is 54 nm. The emission cross-section at 2092 nm is approximately 0.20 × 10 − 20 cm 2 . The broad fluorescence band extends to 2200 nm where almost no absorption was found. The fluoresce lifetime at 2092 nm is 3.73 ms. With the help of up-conversion spectra, the energy transfer mechanism between Tm3+ and Ho3+ ions was investigated systematically. The potential utility of the Tm,Ho:Lu2O3 crystal as tunable and ultra-short laser media at ~2.1 μm can be expected.

The effect of Nd3+ co-doping as sensitizer and deactivator to the Er3+ ion for enhancing ~2.7 μm emissions under 808nm LD pump was first studied in the Er/Nd co-doped PbF2 crystal. The Er0.01Nd0.02Pb0.97F2 crystal has been successfully grown by the Bridgman method, and the crystals’ fluorescence emission properties and energy transfer mechanisms of series crystals were investigated. It can be seen that through the Nd3+ ion, the lower energy level of Er3+: 4I13/2 has been depopulated, and the upper energy level of Er3+: 4I11/2 has been populated at the same time. Simultaneously, the energy transfer efficiency from the Er3+: 4I13/2 level to the Nd3+: 4I15/2 level is 84.06%, and from the Nd3+: 4F3/2 level to the Er3+: 4I11/2 level is 55.81%, respectively, which indicate that the Nd3+ ion is an effective deactivator and sensitizer ion for enhancing the ~2.7 μm emission in Er/Nd: PbF2 crystal. These advantages suggest that the Er/Nd: PbF2 crystal may be a potential material for ~2.7 μm mid-infrared lasers under the 808 nm LD pump.

An in-band pumped passively Q-switched (PQS) self-Raman laser with a c-cut Nd:YVO4 composite crystal is demonstrated for the first time to our knowledge. A Cr4+:YAG composite crystal was utilized to improve the stability and misalignment sensitivity of the resonator. The PQS self-Raman output performance was systematically investigated with different initial transmissions (T0) of the Cr4+:YAG and different transmissions (TS) of the Raman output coupler. In addition, the focus position of the incident pump beam and cavity length have been optimized during the experiment. With Cr4+:YAG of T0=90% and output coupler of TS=10%, the maximum average output power at 1178 nm was up to 2.53 W under the absorbed pump power of 20.6 W, corresponding to an optical-to-optical conversion efficiency of 12.3%. The pulse repetition frequency and pulse width were measured to be 39.1 kHz and 20.4 ns, respectively, and the corresponding pulse energy and peak power were calculated to be 64.7 μJ and 3.2 kW. At the full output power, the fluctuation of Raman output power was less than ±0.5% within one hour. To the best of our knowledge, we have improved the PQS self-Raman laser about 3.2 times.

A diode-side-pumped passively Q-switched laser at 532 nm wavelength by Nd 3+ :YAG/Cr 4+ :YAG/YAG composite crystal is revealed for the first time. The output performances, including the threshold, slope efficiency, average power, pulse width, repetition rate and far field spot of lasers with Cr 4+ :YAG of different initial transmissions are experimentally compared. Under the pump power of 187.5 W, the Q-switched green laser with initial transmission of 85% obtains the maximum average power of 27.2 W and peak power of 7.8 KW. The laser with initial transmission of 65% obtains the pulse width of 59 ns. The initial transmission has significant effects on the output performances of passively Q-switched lasers.

We present a diode-side-pumped Q-switched mode-locked (QML) laser operating at 532 nm for the first time employing a composite crystal Nd:YAG/Cr4+:YAG/YAG and a KTP. The experimental results show that, using a suitable cavity and crystals, one can obtain high-quality QML laser output at 532 nm with a side-pumped system. We measure and analyze the QML performance of the fundamental frequency laser and the green laser. Under a pump power of 127 W, we obtain a QML laser operating at 532 nm with an average power of 4.97 W and a repetition rate of 0.2 GHz for the mode-locked pulses; the corresponding depth of modulation is close to 100%.

The use of Prsup3+/supcodoping for enhancement of the transition of Ersup3+/sup:sup4/supIsub11/2/sub→sup4/supIsub13/2/sub2.7 μm emissions was investigated in the Er/Yb codoped LiNbOsub3/subcrystal for the first time. It is found that the codoped of Prsup3+/supion in Ersup3+/sup, Ybsup3+/supand Prsup3+/suptriply doped LiNbOsub3/subcrystal (Er/Yb/Pr: LN) greatly enhances Ersup3+/sup: 2.7 μm emission under excitation of a common 970 nm laser diode, depopulates the lower laser level of Ersup3+/sup:sup4/supIsub13/2/sub, and has little influence on the higher laser level of Ersup3+/sup:sup4/supIsub11/2/subat the same time for population inversion. The 2.7 μm emission characteristics and energy transfer were investigated in detail. The energy transition efficiency from lower laser level of Ersup3+/sup:sup4/supIsub13/2/subto Prsup3+/sup:sup3/supFsub4/sublevel is as high as 0.42, indicating that the Prsup3+/supion is an effective deactivation ion for Ersup3+/supion in LiNbOsub3/subcrystal. These results suggest that Er/Yb/Pr: LiNbOsub3/subcrystal may become an attractive host for developing solid state lasers at around 2.7 μm under a conventional 970 nm LD pump.

This paper aims at designing and demonstrating a video and audio signals synchronous wireless transmission of free-space optical communication (FSO) system. Video and audio signals were modulated by the acousto-optical modulator (AOM). With the help of a designed circuit and programmable microcontroller, the system based on time division multiplexing (TDM) achieves the functions of signal de-multiplexing and wireless transmitting. Proved by experiments, the system meets the actual requirements with advantages of flexibility, practicality and low cost. And it provides an efficient scheme of synchronous wireless transmission of video and audio signals for monitoring system and TV access network.

The long pulse operation of ultraviolet (UV) laser attributed to multi-reflection is presented on an acousto-optic (AO) Q-switched ultraviolet laser system blocking green light inside a cavity. The ultraviolet laser with the highest average power of 456 mW is obtained with 20 kHz repetition-rate. The numerical simulation of UV pulse broadening was studied using Gaussian curve approximation. The conclusion suggests that the short multi-reflected cavity and high incident pump power will be beneficial to alleviate the width broadening effect. The results, for the first time, would provide the technology for controlling the pulse width of an AO Q-switched DUV laser.

The use of Tb3+ co-doping for the enhancement of Er3+: 4I11/2 → 4I13/2 mid-infrared emissions can conquer the self-termination bottleneck and provide possible applications in medical surgery, dentistry, remote atmospheric sensing, light detection, and the optical parametric oscillator. The effect of Tb3+ co-doping on the fluorescence emission properties and mutual energy transfer mechanisms were investigated. It was found that Tb3+ greatly increased Er3+ 2.7μm emission by depopulating the Er3+: 4I13/2 level while having little influence on the Er3+: 4I11/2 level, leading to a greater population inversion. The energy transfer efficiency from Er3+: 4I13/2 to Tb3+: 7F0 is as high as 90.27%, and the Er3+: 4I11/2 → 4I13/2 fluorescence lifetime ratio (τ(4I11/2)/ τ(4I13/2)) of the Er3+/Tb3+: PbF2 crystal was calculated to be 422.79%, indicating that Tb3+ ion is an excellent deactivator with which the self-termination bottleneck effect was effectively suppressed. All of these factors imply that Er3+/Tb3+: PbF2 crystal may be a promising material for 2.7μm laser applications.

We originally proposed a method for obtaining an orthogonally polarized dual-wavelength Raman laser via a polarized-dependent effect of Raman shifting. Pumping a-cut YVO4 crystal with a passively Q-switched Nd:YAG laser, the system not only emitted a conventional Raman emission at 1175.4 nm but also a Raman emission at 1165.2 nm, which originated from the Raman shifts of 890 cm−1 and 816 cm−1, respectively. The polarization directions of the emissions at 1175.4 nm and 1165.2 nm were found to be along the c-axis and b-axis of the YVO4 crystal respectively, which enabled the orthogonally polarized operation. With a type-II KTP crystal, their sum-frequency generation (SFG) was obtained for the first time, and this result proved that the pulse series of these two emissions were simultaneous.

Bi/Ta double doped Gd0.1Y0.9AlO3 (Bi/Ta:GYAP) near-infrared (NIR) laser crystal was successfully grown. The codoping of Ta5+ was demonstrated to effectively enhance the NIR fluorescence emission in Bi/Ta:GYAP crystal for the first time. The introduced Ta5+ ion can induce the change of valence states from Bi3+ to Bi+ based on the charge compensation mechanism, bringing about the enhanced NIR fluorescence emission. The three NIR fluorescence emission peaks centering at 1005, 1195, and 1280 nm were ascribed to three different Bi+ active centers in Bi/Ta:GYAP crystal. These results suggest that the Bi/Ta:GYAP crystal may have potential applications in NIR broadband lasers.

Ho: LuAG, Yb, Ho: LuAG and Yb, Ho, Pr: LuAG laser crystals with high optical quality were successfully grown by the Czochralski method. Compared with Ho: LuAG and Yb, Ho: LuAG crystals, Yb, Ho, Pr: LuAG crystal not only shows a better absorption characteristic but also exhibits weaker ~2 μm emission, as well as superior mid-infrared (MIR) at ~3 μm emission. The ~3 μm MIR emission intensities of Yb, Ho, Pr: LuAG under excitation of a common 970 nm laser diode (LD) is almost nine times that of the Ho: LuAG crystal and twice as much as that of the Yb, Ho: LuAG crystal. The crystal growth, absorption spectra, J-O parameters, emission spectra, fluorescence lifetimes and the energy transfer mechanism in Yb, Ho, Pr: LuAG crystal were studied in this work. The energy transition efficiency from the lower laser level of Ho3+: 5I7 to Pr3+: 3F2 level is as high as 66.6%, indicating that the Pr3+ ion is an effective deactivation ion for Ho3+ ion in Lu3Al5O12 crystal. All these results show that Yb, Ho, Pr: LuAG crystal may become a promising material for developing solid state lasers at around 3 μm under a conventional 970 nm LD pump.

The use of Tb3+ codoping for the enhancement of the transition of Tm3+:3H4→3F4 ∼1.4 μm emissions was investigated in the Tm3+/Tb3+ codoped (Gd0.5Lu0.5)2SiO5 (Tm/Tb:GLSO) crystal for the first time. The ∼1.4 μm fluorescence emission properties and energy transfer mechanism of the as-grown crystals were investigated in detail. It is found that the codoped of Tb3+ ion in Tm/Tb:GLSO crystal greatly enhances Tm3+:1.4 μm emission under excitation of a common 789 nm laser diode, depopulates the lower laser level of Tm3+:3F4, and has little effect on the upper laser level of Tm3+:3H4 at the same time. The energy transfer efficiency from the Tm3+:3F4 level to the Tb3+:7F0 level is as high as (74.4±1.5)%, indicating that the Tb3+ ion is an effective deactivation ion for enhancing the ∼1.4 μm emission in Tm/Tb:GLSO crystal. These results suggest that Tm/Tb:GLSO crystal may be a promising material for ∼1.4 μm laser under the pump of a conventional 789 nm LD.

In this paper, the continuous-wave intracavity second harmonic generation of a laser diode side-pumped Nd:YAP laser operating in the 1.3-μm region is demonstrated. A type-I critical phase-matched LiB3O5 (LBO) crystal was used as the frequency doubler. 8.1 W/670.7 nm and 5.1 W/669.6 nm continuous-wave red light outputs were achieved from the 1341.4-nm laser beam polarized along the c crystalline axis and the 1339.2-nm laser beam polarized along the a crystalline axis, respectively. The stability of the 670.7-nm red laser is better than 3% at the output power of 7 W in an hour.

In this paper, a diode-side-pumped acoustooptic Q-switched 1319-nm Nd:YAG laser is described. The output characteristics under the different repetition rates and output couplers have been studied. With a pumping power of 555 W, the average output power decreases from 94 W at 50 kHz to 71 W (slope efficiency 25.2%, optical conversion efficiency 12.8%) at 5 kHz. The highest peak power is up to 95 kW with the pulse duration of 150 ns at the repetition rate of 5 kHz.

We report a completely solid-state continuous-wave (CW) blue laser operating at 447 nm utilizing intracavity frequency tripling of an LD-side-pumped Nd:YAlO3 (Nd:YAP) laser operating at 1341.4 nm. An LBO crystal with type-I critical phase matching and a KTP crystal with type-II critical phase matching (CTM) were used for the second harmonic generation (SHG) and the third harmonic generation (THG), respectively. In view of the analysis of the cavity stability, a four-mirror folded cavity was designed and the output characteristics were theoretically analyzed. Experimental characteristics obtained were shown to be in agreement with the theoretical analysis. The maximum output power of the 447 nm CW blue laser reached 114 mW, which corresponds to a red-to-blue conversion efficiency of 9%.

A diode-side-pumped simultaneous dual-wavelength Q-switched Nd:YAG laser around 1.3 μm is demonstrated. With the pumping power of 480 W, a peak power of 43 kW was obtained at the repetition rate of 5 kHz. The maximum average output power is up to 43 W with the slope efficiency of 20.5%, and the pulse duration is 200 ns. This dual-wavelength Q-switched laser with high peak power has a balanceable and stable proportion of dual-wavelength output.

Since the spectral imaging technology emerged, it has gained a lot of application achievements in the military field, precision agriculture and biomedical science. When the fluorescence spectrum imaging first applied to the detection of the feature resource of Chinese herbal medicine, the characteristics of holistic and ambiguity made it a new approach to the traditional Chinese medicine testing. In this paper, we applied this method to study the Chinese medicine north and south isatis root granules by comparing their fluorescence spectra. Using cluster analysis, the results showed that the north and south Banlangen can not be divided by ascription. And these indicate that there is a large difference in the quality of Banlangen granules on the market, and fluorescence spectrum imaging method can be used in monitoring the quality of radix isatidis granules.

Objective To present a case of electrical storm (ES) in a female patient with rheumatic valve disease. Methods A female patient with severe rheumatic valve disease suffered an unexpected ES. She received more than 50 electrical shocks for repeated cardiac arrests due to ES over 16 hours. Then she received beta-blocking agent treatment and had an operation of double valves replacement. Results ES was suppressed by sympathetic blockade with beta-receptor blocker and finally disappeared after the double pathological valves had been replaced. Conclusion Increased sympathetic activity plays an important role in the genesis of electrical storm and sympathetic blockade may effectively suppress ES. However, the most important thing in the treatment of ES is to identify and eliminate the underlying cause of ES.

A high-power CW diode-side-pumped Nd:YAP laser with linearly polarization at 1341 nm has been described. The laser characteristics including thermal lens and stability of flat-flat resonator were studied. By comparing the output powers at different resonator lengths and different output couplers, the c-axis polarized laser working at 1341 nm has been obtained with a maximum output power of 121 W at the pumping power of 555 W. The optical-optical efficiency is 21.8% and the optical slope efficiency is 40%. The a-axis polarized laser at 1339 nm has also been successfully obtained when the c-axis polarized laser had become instable with the increase of pumping power. (c) 2006 Elsevier B.V. All rights reserved.

An experimental study of the influence of external magnetic field on the fluidization behavior of magnetic pearls was carried out. Magnetic pearls are a magnetic form of iron oxide that mainly consists of Fe2O3 which are recovered from a high-volume power plant fly ash from pulverized coal combustion. Due to its abundance, low price and particular physical and chemical properties, magnetic pearls can be used as a heavy medium for minerals or solid waste dry separation based on density difference. This paper introduces the properties of magnetic pearls and compares the performance of magnetic pearls fluidised bed operation with or without an external magnetic field. Experimental results show that an external magnetic field significantly improves the fluidization performance of magnetic pearls such as uniformity and stability.