Search

We experimentally demonstrated a diode-pumped 587 fs ultrafast laser by using an a-cut Nd:CaYAlO

In a batch mixed culture of Propionibacterium acidipropioniai and Saccharomyces cerevisiae, which could exploit synergistic effects, cell growth and propionic acid production rates of P. acidipropioniai significantly increased, compared with those in pure cultures. Compared with a pure culture, the mixed culture had a significant improvement on the maximal propionic acid (12.1 g/l vs. 10.1 g/l) and glycerol conversion efficiency (60.5% vs. 50.5%). Propionic acid production was further enhanced by an addition of glycerol solution in the fed-batch mixed culture; and the maximal propionic acid yield and glycerol conversion efficiency reached 27.9 g/l and 56.7%, respectively. These results showed that a mixed culture of P. acidipropionici and S. cerevisiae could serve as an excellent alternative to conventional propionic acid fermentation.

MASTA is the professional CAE software for auto transmission simulation, analysis and design system. Based on this, firstly how to realize the design and optimization of auto transmission assembly is discussed by MASTA system deflection analysis principle, not only are the accuracy of gear strength and modification analyzed through comparison, but also the selection and rating basis of axis and bearing are obtained. In addition, on basis of the full consideration of the whole structure deflection namely the structural flexibility factor, the influence of the housing and alien shafts’ actual rigidity on internal driving system is checked, and the analysis results of gear strength are presented. A new design concept is put forward, which improves design level of gearbox, and reduces the testing time and shortens the product development cycles as well.

On the basis of the analysis of winding drive system’s technological requirements of multi-wire cutting system and the characteristics of torque motor, the article proposes a scheme of wrap wheel with torque motor control to overcome the deficiency of the general control motor driven wrap wheel. In determination process of winding system parameter, it provides the selective calculation methods and the control strategy of the torque motor. According to processing materials, we get tension values, and then calculate the output torque, and choose a suitable torque motor and determine the control strategy. Then the design process of winding drive system finishes. Adopting the torque motor as wrap wheel control motor can make wrap device to meet the system requirements. Meanwhile it can simplify the structure of wrap device, and make the cutting-process runs smoothly.

An alternately intermittent oscillation technique was proposed and an intermittent oscillation dual-wavelength diode side-pumped solid-state laser has been set up. The model of rate equations of intermittent oscillation dual-wavelength laser has been considered. By this means, the population inversion was distributed efficiently, mode competition of both laser lines can be avoided, the effect resulted from the accuracy of the coating process can be reduced and the stable output of dual-wavelength was easily obtained. What is more, for different operation condition, the ratio of the output powers can be controlled by changing the delay time, so it is very beneficial to all-solid-state RGB lasers.

We demonstrate a laser-diode-pumped Q-switched 1329 nm neodymium-doped calcium-niobium-gallium-garnet (Nd:CNGG) laser using a V:YAG crystal as a saturable absorber. An average output power of 353 mW and a repetition rate of 13.43 kHz for Q-switched pulses were obtained. The pulse width was from 124 to 151.4 ns under different pump powers. Output power of 685 mW was obtained without the V:YAG crystal inserted.

We have demonstrated a self-staring passively continuous-wave mode-locked diode end-pumped Nd:YLF laser with a semiconductor saturable absorber mirror of single-quantum-well (In0.25Ga0.75 As) grown by metal-organic chemical-vapor deposition technique at low temperature. The saturable absorber was used as nonlinear absorber and output coupler simultaneously. Stable pulse duration of 3 ps has been achieved at the repetition rate of 98 MHz. The average output power was 530 mW at 1053 nm under the incident pump power of 10 W, corresponding to the peak power of 1.8 kW and pulse energy of 5.4 nJ

The continuous-wave and acousto-optical Q-switched pulse laser properties of diode-pumped Nd:YAG crystal operating at 946 nm formed with a simple plane–plane cavity have been studied. Extra-cavity single-pass quasi-phase matching (QPM) frequency doubling with periodically poled LiTaO3 (PPLT) as the nonlinear crystal yielded a maximum output power of 66 mW at 473 nm with an overall optical to optical efficiency of 14.2% from 946 to 473 nm. Our result proves that this scheme is of practical value for the construction of a blue all-solid-state laser.

Low temperature GaAs (LT-GaAs) was successfully grown at the temperature of 550 degrees C by metal organic vapor phase epitaxy on a semi-insular GaAs substrate. With such an absorber as well as an output coupler we obtain Q-switched mode-locked (QML) 1064 nm Nd:GdVO4 laser pumped by diode laser with high repetition rate, formed with a simple flat-flat cavity. The repetition rate of the Q-switched envelope increased from 100 to 660 kHz as the pump power increased from 2.28 to 7.29 W. The mode-locked pulses inside the Q-switched pulse envelope had a repetition rate of similar to 1.36 GHz. A maximum average output power of 953 mW was obtained. The dependence of the operational parameters on the pump power was also investigated experimentally. (C) 2005 Elsevier B.V. All rights reserved.

We have demonstrated an efficient and compact passively Q-switched and mode-locked (QML) 1064 nm Nd:YVO4 laser by using a low temperature grown GaAs (LT-GaAs) saturable absorber as well as an output coupler. Stable QML with envelope duration as short as 10 ns and Q-switched repetition rate of 36 kHz was obtained. It is the shortest envelope duration as far as we know, and it is so short that it can be used as Q-switching pulses directly. At 6.9 W of the incident pump power, average output power of 1.24 W was achieved and the corresponding peak power and energy of a single Q-switched pulse were 3.44 kW and 34.4 mu J, respectively. The mode-locked pulses inside the Q-switched pulse envelope had a repetition rate of 780 MHz. (C) 2005 Elsevier B.V. All rights reserved.

Simultaneous Q-switching and mode-locking (QML) is accomplished in a diode-pumped Nd:YAG laser using low-temperature GaAs (LT-GaAs) as the saturable absorber, which also acts as an output coupler at the same time. The repetition rate of the Q-switched envelope increased from 25 to 40 kHz as the pump power increased from 2.2 to 6.9 W. The mode-locked pulses inside the Q-switched pulse envelope had a repetition rate of 714 MHz. A maximum average output power of 770 mW was obtained.

In this paper, we report how to realize an all-solid-state laser with an efficient dual-wavelength red and green light output by temperature tuning. This laser is constructed with a nonlinear crystal and a diode-pumped, Q-switched Nd?:?YVO4 laser as the fundamental source with the dual-resonance wavelengths at 1342 and 1064?nm. The nonlinear crystal is a specially designed superlattice that is able to achieve quasi-phase-matched frequency doubling of 1342 and 1064?nm at two phase-matching temperatures. Using this scheme, 520?mW red light and 332?mW green light are generated at 118.5?C and 113?C, respectively, from two moderate fundamental powers with an efficiency of around 25?30%. The results provide a possible scheme for obtaining multi-wavelength output from a mono-laser by only adjusting the operating temperature.

To investigate the possible roles of adenosine and the cytokines TNF-alpha and IL-10 in the pathogenesis of acute bacterial prostatitis (ABP) in rats.Forty-eight male Wistar rats were randomly divided into groups A (ABP), B (ABP + theophylline intervention), C (sham) and D (blank control). ABP models were established by injecting Escherichia coli 0157 into the prostate, and those in group B were treated by intraperitoneal injection of theophylline immediately after modeling. At 4 and 14 days, the prostate tissues of the rats were collected for detection of the expressions of TNF-alpha and IL-10 by immunohistochemistry and the concentration of adenosine by high-performance liquid chromatography.At 4 and 14 days, the concentrations of adenosine were significantly higher in group A ([48.38 +/- 17.27] and [26.54 +/- 11.22] microg/g) than in C ([0.45 +/- 0.25] and [0.46 +/- 0.29] microg/g) and D ([0.41 +/- 0.23] and [0.43 +/- 0.27] microg/g) (P0.05), and so were the expressions of TNF-alpha in A (0.23 +/- 0.08 and 0.21 +/- 0.03) than in C (0.07 +/- 0.03 and 0.07 +/- 0.01) and D (0.07 +/- 0.06 and 0.07 +/- 0.06) (P0.05), and those of IL-10 in A (0.13 +/- 0.03 and 0.25 +/- 0.01) than in C (0.07 +/- 0.03 and 0.07 +/- 0.03) and D (0.07 +/- 0.01 and 0.07 +/- 0.02) (P0.05). Compared with group A, the rats in group B showed significant increases at 4 and 14 days in the severity of inflammation, concentration of adenosine ([86.64 +/- 32.87] and [51.17 +/- 22.96] microg/g, P0.05) and expression of TNF-alpha (0.37 +/- 0.08 and 0.32 +/- 0.06, P0.05), but exhibited no remarkable difference in the expression of IL-10 (0.12 +/- 0.06 and 0.15 +/- 0.06, P0.05).Adenosine may affect the progression of inflammation by regulating the expressions of the cytokines TNF-alpha and IL-10 in ABP rats through the adenosine receptor signaling pathway.

The generation of ultraviolet (UV) light at 335.5 nm based on frequency quadrupling of a diode-end-pumped Q-switched Nd:YVO4 laser at 1342 nm was demonstrated. KTP crystal was used for generation of wavelength of 671 nm by intracavity doubling and LBO (BBO) crystal was exploited for the subsequent external fourth harmonic generation (FHG). With 6.3-W absorbed pump power and 10-kHz frequency repetition rate, the UV output power of 35 and 63 mW were obtained by using LBO and BBO as frequency quadrupling nonlinear crystals, respectively. The experimental results show that the conversion efficiency (red-UV) of 6.4% for BBO crystal is higher than that of 3.5% for LBO crystal, but the UV beam quality obtained by LBO crystal is better than by BBO crystal.

A coherent UV passively Q-switched diode pumped Nd:GdVO4 laser source is proposed. During pumping of the β-BBO crystal a stable light with power 0.6 W with wavelength 532 nm and pulse duration 9 ns at frequency repetition 16 kHz was applied. The output UV light has a power about 79 mW at wavelength 266 nm during diode-pumping with 8 W incident light.

A highly efficient and high power green laser generated by intracavity frequency doubling of a diode-sidepumped Q-switched Nd: YAG laser has been demonstrated. In the simple L-shaped cavity geometry, the maximum green output power of 28.5 W was obtained with a pulse width of 95 ns at a pulse repetition rate of 10 kHz by using a LBO crystal for frequency doubling, corresponding to a conversion efficiency of 11% from diode pump power to pulse green power. At a pulse repetition rate of 1. kHz, 6.9 mJ of pulse energy, 25 ns of pulse duration and 276 kW of peak power were obtained.

In the present study, we evaluated the safety and efficacy of immediate surgical bipolar plasmakinetic transurethral resection of the prostate (PK-TURP) for patients with benign prostatic hyperplasia (BPH) with acute urinary retention (AUR). We conducted a retrospective analysis of clinical data of BPH patients who received PK-TURP. A total of 1126 BPH patients were divided into AUR (n = 348) and non-AUR groups (n = 778). After the urethral catheters were removed, the urine white blood cell (WBC) count in the AUR group significantly increased compared with the non-AUR group (P < 0.01). However, there was no significant difference in international prostate symptom score, painful urination, and maximal urinary flow rate. The duration of hospitalization of the AUR group was longer than that of the non-AUR group (P < 0.001). A total of 87.1% (303/348) patients in the AUR group and 84.1% (654/778) patients in the non-AUR group completed all of the postoperative follow-up visits. The incidence of urinary tract infection in the AUR group within 3 months after surgery was significantly higher than that in the non-AUR group (P < 0.01). The incidence of temporary urinary incontinence in the AUR group did not exhibit significant difference. During 3-12 months after surgery, there were no significant differences in major complications between the two groups. Multivariate regression analyses showed that age, postvoid residual, maximal urinary flow rate, diabetes, and hypertension, but not the presence of AUR, were independent predictors of IPSS post-PK-TURP. In conclusion, immediate PK-TURP surgery on patients accompanied by AUR was safe and effective.

Accurate knowledge of the spinal structural functions is critical to understand the biomechanical factors that affect spinal pathology. Many studies have investigated the human vertebral motion both in vitro and in vivo. However, determination of in vivo motion of the vertebrae under physiologic loading conditions remains a challenge in biomedical engineering because of the limitations of current technology and the complicated anatomy of the spine.For in vitro validation, a human lumbar specimen was imbedded with steel beads and moved to a known distance by an universal testing machine (UTM). The dual fluoroscopic system was used to capture the spine motion and reproduce the moving distance. For in vivo validation, a living subject moved the spine in various positions while bearing weight. The fluoroscopes were used to reproduce the in vivo spine positions 5 times. The standard deviations in translation and orientation of the five measurements were used to evaluate the repeatability of technique. The accuracy of vertebral outline matching with metallic marks matching technology was compared.The translation positions of the human lumbar specimen could be determined with a mean accuracy less than 0.35 mm and a mean repeatability 0.36 mm for the image matching technique. The repeatability of the method in reproducing in vivo human spine six degrees of freedom (6DOF) kinematics was less than 0.43 mm in translation and less than 0.65° in rotation. The accuracy of metallic marks and vertebral outline matching did not show significant difference.Combining a dual fluoroscopic and computerized tomography imaging technique was accurate and reproduceable for noninvasive measurement of spine vertebral motion. The vertebral outline matching technique could be a useful technique for matching of vertebral positions and orientations which can evaluate and improve the efficacy of the various surgical treatments.

With the agility of cavity control in solid-state-laser, we report abundant experimental phenomena of relatively complete Laguerre-Gaussian (LG) transverse multimodes transformation process including both stable and transitional status in a diode pumped Nd:YVO4 microcavity laser. Cavity structure, absorber, pump power, etc, synthetically have been found to contribute such abundant generation of patterns.

The performance of a passively Q-switched all-solid-state Nd:YVO4 laser using Cr4+:YAG as saturable absorber is reported. Optimum coupling operation at 1064 nm resulted in 70 ns pulses at 40 kHz repetition rates with average output power of 2.1 W. A quantitative theoretical description agrees well with the experimental results.

With a type-I noncritically phase-matched LiB3O5 crystal as the intracavity frequency doubler in a diode pumped Nd:YVO4 laser, 440 mW of 671 nm light was obtained at 5.5 W of incident pump power, the optical-optical conversion efficiency being 8.0%.

Optical superlattice Er:LiNbO3 was fabricated by inducing a periodic ferroelectric domain structure into the crystal during the growing process. Because of the combination of the nonlinear optical properties of LiNbO3 and the spectral properties of Er3+, the crystal can simultaneously emit the second harmonic light through quasi-phase matching and the green light through upconversion at room temperature. Pumped by infrared diode lasers, violet-and-green and blue-and-green light generation was demonstrated in two samples. The detailed absorption spectrum and emission spectrum of upconversion were measured. The possible physical mechanism was discussed.

We have demonstrated a passively mode-locked diode end-pumped all-solid-state laser, which is composed of a Nd:Gd0.5Y0.5VO4 crystal and a folded cavity with a semiconductor saturable-absorber mirror grown by metal-organic chemical-vapor deposition. Stable cw mode locking with a 3.8-ps pulse duration at a repetition rate of 112 MHz was obtained. At 13.6 W of the incident pump power, a clean mode-locked fundamental-mode average output power of 3.9 W was achieved with an overall optical-to-optical efficiency of 29.0%, and the slope efficiency was 38.1%.

A cw laser-diode-pumped Yb-doped double-clad fiber laser operating in a hybrid Q-switched regime was demonstrated. The output pulses had a duration as short as 4.2 ns, a tunable wavelength range from 1080.8 to 1142.7 nm, and a linewidth of less than 0.05 nm. Maximum peak power of approximately 175 kW and single-pulse energy of 1.57 mJ were obtained.

A new algorithm for precise determination of the global phase shift between two interferograms is introduced. First we calculate the frame difference between the first and the second interferogram; the difference is multiplied by a properly chosen test phase factor, and then we implement a two-dimensional Fourier transform of the frame difference and calculate the energy of the first positive (or negative) diffraction order. An iterative approach is used for the test phase to ensure that the minimum energy is obtained, and then the correct phase shift value is found. This method is called the energy-minimum Fourier transform method, which is accurate and noise insensitive compared with the single-point Fourier transform method. Both the theoretical analysis and experimental results are given.

We report a theoretical study of the simultaneous high-efficiency, equal-level outputs of second and third harmonics in a quasiperiodic optical superlattice at any given fundamental intensity. The principle is that nonlinear coupling is effectively controlled by introducing proper quasiphase mismatches, by use of the tunability of linear refractive index gratings induced by applying a dc electric field based on the electro-optic effect. The theoretical results verify that this approach is feasible and very efficient. In addition, we also make a comparison with temperature tuning control, demonstrating that the performance of electro-optic control is much better than that of temperature tuning control.

We report on a noniterative method for coherent diffractive imaging based on a specially designed multipinhole (MP) plate. We demonstrated that the complex amplitude of the wavefront penetrating through an MP plate inserted between the specimen and the detector plane can be directly extracted from the Fourier transform of a single far-field diffraction intensity pattern without need of any iterative algorithm. A form of scanning diffractive imaging based on a rotatable MP plate is also demonstrated, which provides a feasible approach for lensless diffractive imaging of complex-valued objects.

A maximum of 5.5 W of cw TEM00 mode output at 532 nm has been obtained by intracavity frequency doubling with a KTP crystal in an Nd: YVO4 laser doubly-pumped with 20 W diode pumping power. The optical-optical conversion efficiency is 27.5%. The influence of thermal lensing at high pumping power in the end-pumped Nd:YVO4 laser is discussed. The Nd:YVO4 laser has a good power stability of 1.6%.

We have demonstrated a diode-pumped Nd:YVO4 laser that produced 273mW cw output at 671nm by using KTP intracavity doubling. The optical-optical efficiency of the all-solid-state red laser was 5.1%. The maximum output power of the fundamental wave at 1342 nm from Nd:YVO4 was 2.3W with slope-efficiency of 43%.

We made a theoretical investigation on the top-hat-beam Z scan when the nonlinear media possess third- and fifth-order nonlinearities simultaneously. A high-accuracy method was proposed to allow the determination of the nonlinear refraction coefficients related to the third- and fifth-order effects. We also reconfirmed the common procedure for dividing the contributions of the third- and fifth-order effects to the nonlinearity in the top-hat-beam Z-scan measurements; the results indicated that the common procedure can be still employed for the determination of the third-order nonlinearity, whereas it is inapplicable for the fifth-order nonlinearity. We investigated experimentally, as a test, the nonlinear refraction of a Disperse Yellow 7 thin film by using the top-hat-beam Z-scan technique, with 35-ps-duration pulses at a 1064-nm wavelength.

We report a theoretical study of the Z-scan technique by using quasi-one-dimensional slit beams for characterizing third-order optical nonlinearity. We verify that the sensitivity of this Z-scan scheme is roughly the same level as top-hat beams and is greatly higher than Gaussian beams by a factor of approximately 2.5. This scheme should have the capability to measure less than a λ/500 wave-front distortion at least. Numerical formulas obtained in theory allow direct estimation of nonlinear refraction and absorption coefficients from the normalized peak–valley transmittance difference measured. Some salient features are also discussed. This Z-scan scheme is also demonstrated experimentally.

An idea of an optimal annulus structure phase mask with helical wavefront is suggested; the resulting helical mode can be focused into a very clear optical vortex ring with the best contrast. Dependences of the optimal annulus width and the radius of the optical vortex ring on topological charge are found. The desired multi-optical vortices as the promising dynamic multi-optical tweezers are realized by extending our idea to the multi-annulus structure. Such multi-optical vortex rings allow carrying the same or different angular momentum flux in magnitude and direction. The idea offers flexibility and more dimensions for designing and producing the complicated optical vortices. For the Gaussian beam illumination, the optimal spot size, which ensures the high energy/power efficiency for generating the best contrast principal ring is also found.