Publications by authors named "Ling-qiang Meng"

6 Publications

  • Page 1 of 1

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

Appl Opt 2019 Apr;58(11):2765-2772

In this paper, a new method for measuring the beam quality (M) 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 M 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 M of lasers can be measured faster with the proposed method.
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http://dx.doi.org/10.1364/AO.58.002765DOI Listing
April 2019

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

Appl Opt 2018 Jan;57(3):485-491

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.
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http://dx.doi.org/10.1364/AO.57.000485DOI Listing
January 2018

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

Appl Opt 2018 Jan;57(2):130-137

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 (M). 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 M is simulated. The experimental results demonstrate that the new method can be an effective means to measure the M 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 M.
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http://dx.doi.org/10.1364/AO.57.000130DOI Listing
January 2018

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

Appl Opt 2017 Sep;56(27):7596-7603

A complete complex amplitude reconstruction method for the determination of the laser beam quality factor M 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 M factor is provided. The experimental results demonstrate that the new method can be an accurate means to measure the M factor. The proposed method can avoid the influence of phase inaccuracy in the small signal area of the interferogram, during the measurement of the M factor.
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http://dx.doi.org/10.1364/AO.56.007596DOI Listing
September 2017

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

Hua Xi Kou Qiang Yi Xue Za Zhi 2010 Oct;28(5):505-8

Dept. of Stomatology, The First Hospital of Hebei Medical University, Shijiazhuang 050031, China.

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.
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October 2010

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

Shanghai Kou Qiang Yi Xue 2008 Feb;17(1):67-70

Department of Prosthodontics, Stomatological Hospital, Hebei University of Medical Sciences, Shijiazhuang 050017, Hebei Province, China.

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).
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February 2008
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