Fast measurement of the laser beam quality factor based on phase retrieval with a liquid lens.

In this paper, a new method for measuring the beam quality (M2) of lasers based on phase retrieval with a liquid lens is proposed. With intensity profiles obtained under different focal lengths in a certain position, a variable-focus iterative retrieval algorithm is established for the reconstruction of the complex amplitude. Then M2 can be calculated with the angular spectrum theory. Feasibility of the proposed method is demonstrated with single- and multimode lasers through both simulations and experiments. Compared with the traditional liquid lens method, the M2 of lasers can be measured faster with the proposed method.

Suppressing the influence of charge-coupled device vertical blooming on the measurement of laser beam quality factor (M2) of a near-infrared laser.

In this paper, a new method, which is based on reconstructing the original intensity distribution of a laser with images captured by a charge-coupled device (CCD) in two orthogonal directions, is proposed for suppressing the influence of CCD vertical blooming on the measurement of the laser beam quality factor (M2). A simplified theoretical model for the distribution of CCD blooming is also proposed. With the proposed method and model, the influence of CCD vertical blooming on the measurement of M2 is simulated. The experimental results demonstrate that the new method can be an effective means to measure the M2 of a near-infrared laser with a silicon CCD camera. The proposed method can be applied to a beam quality analyzer in order to suppress the influence of blooming on the measurement of M2.

Heat suppression of the fiber coating on a cladding light stripper in high-power fiber laser.

We present a theoretical model for the thermal effect of the fiber coating on a high-power cladding light stripper, which is fabricated by chemical etching. For the input and output of the fiber coating, a novel segmented corrosion method and increasing attenuation method are proposed for heat suppression, respectively. The relationship between the attenuation and temperature rise of the fiber coating at the output is experimentally demonstrated. The temperature distribution of the fiber coating at the input as well as the return light power caused by scattering are measured for the etched fiber with different surface roughness values. The results suggest that the rise in temperature is primarily caused by the scattering light propagating into the coating. Finally, an attenuation of 27 dB is achieved. At a room temperature of 23°C and input pump power of 438 W, the highest temperature of the input fiber coating decreases from 39.5°C to 27.9°C by segmented corrosion, and the temperature rise of the output fiber coating is close to 0.

Determination of the laser beam quality factor (M2) by stitching quadriwave lateral shearing interferograms with different exposures.

A complete complex amplitude reconstruction method for the determination of the laser beam quality factor M2 based on the multiple exposure of a quadriwave lateral shearing interferometer (QWLSI) is presented. The theoretical analysis and simulation of the influence of the information in the small signal area on the calculation of the M2 factor is provided. The experimental results demonstrate that the new method can be an accurate means to measure the M2 factor. The proposed method can avoid the influence of phase inaccuracy in the small signal area of the interferogram, during the measurement of the M2 factor.

The Impact of Emotional Leadership on Subordinates' Job Performance: Mediation of Positive Emotions and Moderation of Susceptibility to Positive Emotions.

Employees' emotions have an important effect on their job performance, thus leaders can influence subordinates' emotions through emotional contagion and emotional appeal and ultimately affect their job performance. Based on the affective events theory, this study examines the impact of emotional leadership on the subordinates' job performance, the mediating role of subordinates' positive emotions, and the moderating role of susceptibility to positive emotion. Hierarchical regression analysis of 362 valid questionnaires showed that: (1) emotional leadership has a significant positive effect on subordinates' job performance; (2) subordinates' positive emotion partially mediated the relationship between emotional leadership and subordinates' job performance; (3) subordinates' susceptibility to positive emotion positively moderated the relationship between emotional leadership and positive emotions, i.e., the higher the subordinates' susceptibility to positive emotion, the greater the effect of emotional leadership on their positive emotions. This study validates affective events theory, deepens the understanding of the influence mechanism and boundary conditions of emotional leadership on subordinates' job performance, and provides some references for employee performance management.

[The effect of the metallic dental materials on magnetic resonance imaging].

OBJECTIVE: To explore the influence of conventional metal materials in oral cavity on brain magnetic resonance imaging (MRI). METHODS: Four kinds of metal materials (metal ligature wire, forging hard and slotless denture, casting nichrome denture, casting copper alloy denture) in oral cavity were scanned through MRI. FSE sequence T1 weighted imaging (FSE T1), EPI diffusion-weighted imaging (DWI) sequence of ordinary, Propeller DWI imaging were used. RESULTS: In FSE T1 sequence, metal ligature wire and forging hard and slotless denture produced serious false image, casting nichrome denture produced moderate false image, casting copper alloy denture produced only little false image. In EPI DWI sequence, obvious magnetic-sensitive false image were produced in the dissection tissue of the brain by metal ligature wire. While in Propeller DWI sequence, magnetic-sensitive false image were greatly reduced and satisfactory images were formed. CONCLUSION: Different metal materials in oral cavity have different influence on the MRI. The false images produced by different metal materials are closely related to the type of the material. Magnetic-sensitive false images can be eliminated by Propeller DWI technique.

[The effect of different roughness of crown alloy materials on the adhesion of predominant peri-implant subgingival bacteria].

PURPOSE: To investigate the effect of two crown metal alloys with different roughness on the adhesion of predominant subgingival bacteria. METHODS: Au- Pt alloy and Ni-Cr alloy with different roughness were attached to the Ti implant material and incubated under anaerobic condition. The adhesion of four subgingival predominant bacteria: Porphyromanus gingivalis(Pg), Actinobacillus actinomycet-emcomitans (Aa), Prevotella intermedia (Pi) and Fusobacterium nuclertum (Fn), was detected, respectively. The quantity of bacteria clones on the different surface was counted by means of clone forming unit (CFU) method, and the shape and the growth characteristics of adhered bacteria were observed under scanning electron microscopy (SEM). The date was analyzed using SPSS13.0 software package. RESULTS: The amounts of the four subgingival predominant bacteria adhered to rougher surface of same alloy samples increased significantly (P<0.01), and the amount of bacteria adhered to the surface of Au-Pt alloy samples was much more than that to alloy Au-Pb samples with the same roughness (P<0.01). CONCLUSIONS: The effect of Au-Pt alloy is significantly greater than Au-Pb alloy to the adhesion of bacteria. The amount of bacteria adhered to rougher surface of same alloy samples is more than those to smooth one. Supported by Research Fund from Bureau of Science and Technology of Hebei Province(Grant No.032761961D-46).