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The 946nm diode-pump microchip self-Q-switched laser of a chromium and neodymium codoped yttrium aluminum garnet crystal material (Cr4+Nd3+:YAG) is studied, especially about its physical mechanism of operation. The 4F3/2 → 4I9/2 transition of Nd3+ ion is beneficial to achieving laser oscillation in a quasi-three-level system based on coating the cavity mirrors of the microchip with films that suppress the 1064nm operation and enhance the 946nm laser. The Cr4+ ion is a saturable absorber. The initial loss Nt1 is high, which acts as the threshold for laser oscillation. The stable loss Nt2 is low because the Cr4+ ion is acceleratively bleached by the fast enhancement of the oscillating laser. The high Nt1, small Nt2 and fast progresses permit the oscillating laser of the Cr4+Nd3+:YAG to have a good self-Q-switched property whose full width at half maximum is about 4.2ns. Its highest laser power is about 5.7mW. Its peak power is about 150W. Its good fundamental transverse TEM00 mode results from the absorption bleaching established by both the pump and oscillating lasers, which suppress other transverse mode and allow the oscillation only in the fundamental transverse TEM00 mode.

High power fiber lasers and amplifiers are widely used in the scientific and industrial field. In order to meet the requirements for high output powers the effective area of fibers becomes larger and larger to reduce optical nonlinearities. With the increase of effective area, the number of high-order modes will increase. In the case of high output power, the spectral shift and broadening of the optical fiber will also affect the modal number and content. The number and content of fiber modes affect the pointing stablity and quality of the laser beam. The M2-parameter is commonly used to define the quality of the laser beam, but a small M2 number is not guaranteed for single mode operation. Therefore, the relationship between wavelength and transmission mode in fiber transmission is studied in this paper. We use the spatial and spectral Fourier transform (F2) method to establish a theoretical-experimental method of describing the relationship between wavelength and mode. This method can directly give out the modal content of optical fibers without any priori parameter such as the properties of fiber and requirement for setup accuracy. On the one hand, the theoretical modeling of wavelength affects modal content. In the simulation, the sources with the same wavelength bandwidth and different central wavelengths are used to test the fiber. The results show that the modal content and number of the fiber change with the wavelength bandwidth and center wavelength. The mode components of the corresponding optical fiber will change after changing the central wavelength. As the spectral width of the light source increases, the number of high-order modes increases. On the other hand, in order to further verify the relationship between wavelength and mode of fiber, the F2 method is used to measure the optical fiber modal content with different wavelengths. The final experimental results are in agreement with the theoretical results. The experimental and simulation results show that the mode field distribution of each mode varies with wavelength:the longer the wavelength, the larger the mode field is. The beam quality has little change with the wavelength except for those positions with frequency near the cutoff frequency, and the power ratio of each mode relates to the wavelength.

In this article we consider a finite capacity queuing model in which jobs (or customers) arrive according to a nonrenewal process. The jobs are processed by a single server in groups of varying size, between a predetermined threshold value and the buffer size. A dynamic probability rule is associated with the service mechanism. The services are assumed to be exponential whose parameter may depend on the group size. The steady-state analysis of this queuing model is performed using Markov chain theory. It is shown that the idle period of the server and the stationary waiting time of an admitted job are of phase type and that the departure process can be modeled using a versatile Markovian point process. Efficient algorithms for computing various performance measures such as throughput, mean number served, job overflow probability, server idle probability, the stationary mean waiting time, and the stationary mean idle time of the server, useful in qualitative and quantitative interpretations are developed. Some illustrative numerical examples are discussed.

We investigate the relationship between the beam intensity and the four-wave mixing diffraction efficiency of the longitudinal-field multiple-quantum-well (LMQW) photorefractive device grown at low temperature. A optimum beam intensity is found. We also explain the different mechanisms of the beam intensity effect on the diffraction efficiency of the LMQW device and the transverse-field MQW device. Some advice on how to improve the diffraction efficiency is given.

Based on the investigation of fault rocks from several major fault zones in China, this paper deals with the microstructural features of deformed rocks across the brittle-ductile transition and three types of coexistence of different deformation microstructures are summarized. These are: (i) Coexistence of different deformation microstructures of same mineral, for example, feldspar shows both brittle and ductile deformation features; (ii) Coexistence of different deformation microstructures of different minerals, for example, in same mylonite specimen quartz shows completely ductile deformation features while feldspar shows brittle deformation features; (iii) Coexistence of different deformation microstructures of same mineral at different scale, for example, feldspar shows ductile flow features without fractures under the optical microscope while quartz shows microfractures and “microcrashed zones” under TEM. The authors consider that these coexistence of different deformation microstructures should be helpful to study and understand the process of rock deformation across the brittle-ductile transition.

A stable low-threshold self-Q-switched diode-pumped 946-nm Nd(3+), Cr(4+):YAG microchip laser operating in single frequency and fundamental transverse mode is reported. The output characteristics of the microchip laser were investigated under cw and pulsed pumping. By combination of the infrared microchip and an external frequency doubler, 473-nm pulses with a conversion efficiency of 18% were achieved.

AIM: To evaluate total embolization of the main splenic artery in patients with splenic artery aneurysms (SAAs) and normal spleen. METHODS: Thirty-five consecutive patients with SAAs were referred for treatment with coil embolization. Patients were classified into two groups: coil embolization of the main splenic artery with complete occlusion of the artery and aneurysms (group A, n = 16), and coil embolization of the aneurysmal sac with patency of the splenic artery (group B, n = 19). Data on white blood cell (WBC) and platelet counts, liver function, and complications were collected on days 7 and 30, and subsequently at a 6-mo interval postoperatively. Abdominal computed tomography was routinely performed to calculate the splenic volume before and 1 mo after the procedure, and subsequently every 6 mo during follow-up. RESULTS: Coil embolization of the SAAs was technically successful in all 35 patients, with no procedure-related complications. The post-embolization syndrome, including abdominal pain, fever and vomiting, occurred in six patients (37.5%) in group A and three patients in group B (15.8%). There were no significant differences in WBC and platelet counts between preoperatively and at each follow-up point after the procedures. There were also no significant differences in average WBC and platelet counts between the two groups at each follow-up point. There were significant differences in splenic volume in group A between preoperatively and at each follow-up point, and there were also significant differences in splenic volume between the two groups at each follow-up point. CONCLUSION: Total embolization of the main splenic artery was a safe and feasible procedure for patients with SAAs and normal spleen.