Gang Niu

Northeast Institute of Geography and Agroecology, Peping, Beijing, China

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Publications (18)22.37 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We realized a LD-side-pumped passively Q-switched Nd:YAG laser at 1123 nm by using a single walled carbon nanotube saturable absorber (SWCNT-SA). The SWCNT film was prepared by a vertical evaporation method on quartz substrate. At the pump power of 98 W, a maximum output power of 680 mW for a stable Q-switching operation was obtained. The repetition rate varied from 15.1 kHz to 37.2 kHz with the increase of pump power. The highest single pulse energy of 12.29 μJ occurs at the repetition frequency of 24.4 kHz. The corresponding pulse width was measured to be 2.2 μs.
    Optics Communications 01/2013; 286:261–264. · 1.44 Impact Factor
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    ABSTRACT: We report on a LD-end-pumped passively Q-switched Nd:YAG ceramic laser by using a novel single wall carbon nanotube saturable absorber (SWCNT-SA). The SWCNT wafer was fabricated by electric Arc discharge method on quartz substrate with absorption wavelength of 1064 nm. We firstly investigated the continuous wave (CW) laser performance and scattering properties of Nd:YAG ceramic sample. For the case of passively Q-switched operation, a maximum output power of 376 mW was obtained at an incident pump power of 8.68 W at 808 nm, corresponding to an optical–optical conversion efficiency of 4.3%. The repetition rate as the increase of pump power varied from 14 to 95 kHz. The minimum pulse duration of 1.2 μs and maximum pulse energy of 4.5 μJ was generated at a repetition rate of 31.8 kHz.
    Optics & Laser Technology 10/2012; 44(7):2149–2153. · 1.37 Impact Factor
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    ABSTRACT: Simulation and experimental results for high repetition rate all-normal dispersion Yb:fiber ring lasers are demonstrated for the cavity dispersion from 0.01 to 0.025 ps2. The simulation shows that the pulse spectrum has the potential to reach > 30 nm for the dispersion of 0.014 ps2 under practical pump power. This potential is proved by the experiment. Maximum spectral width of 30 nm is achieved at the repetition rate of 285 MHz under the 850-mW pump power. Average output power is 550 mW and dechirped pulse is 78 fs.
    Chinese Optics Letters 02/2012; 10(3):033201. · 1.07 Impact Factor
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    ABSTRACT: In this paper, we describe a compact all-fiber-path picosecond pulse based on Ytterbium doped fiber oscillator. A home-made novel SESAM mounted on fiber is reported, by which stable mode locking is obtained. The SESAM possesses the low saturation flux 20 μJ/cm2 (versus prior low saturation flux 32 μJ/cm2), which effectively reduces the pump power threshold of mode locking. The fiber laser generates 15 ps pulse trains without a dispersive delay line or anomalous dispersion in the cavity. Mode locking pulse with 30 MHz basic repetition-rate was produced, with 10–30 mW scale average output power at 1064 nm. Through 60 h of uninterrupted laser operating, mode locking is steady as ever.
    Laser Physics 06/2011; 21(6):1103-1107. · 2.55 Impact Factor
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    ABSTRACT: We report a semiconductor saturable absorber mirror (SESAM) with phase shift compensation. The SESAM shows a uniform low-intensity reflectivity and a modulation depth up to 12% for the wavelength from 1000 to 1100 nm. A linear cavity all-normal dispersion Yb-doped fiber laser has proved its mode locking performance for the wavelength of both 1030 nm and 1064 nm. KeywordsYb:doped fiber laser–semiconductor saturable absorber–mode locking
    Chinese Science Bulletin 01/2011; 56(13):1348-1351. · 1.37 Impact Factor
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    ABSTRACT: We present a picosecond laser system with high energy by technologies of cavity dumping and amplifying. Firstly, pulses with 10 ps and ∼520 nJ were obtained by cavity-dumped mode-locked laser at 10 kHz repetition rate. Secondly those pulses were seeded into a side-pumped regenerative amplifier (RA). Then pulses output from the regenerative amplifier were amplified by two four-pass post amplifiers. From the laser system pulses with an average power of 30 W corresponding to 3 mJ pulse energy were achieved with the pulse-width of 25.4 ps at repetition rate of 10 kHz.
    Laser Physics 01/2011; 21(6):1042-1046. · 2.55 Impact Factor
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    ABSTRACT: appearance of multiple pulsing, and give an explanation with regard to establishment of multiple pulsing. The fiber laser generates 15 ps pulse trains without a dispersive delay line or anomalous dispersion in the cavity. Mode locking pulse with 17 MHz low repetition-rate was produced, with 10 mW average output power at 1064 nm.
    01/2011;
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    ABSTRACT: We report on a passively mode-locked erbium-doped fiber laser with a repetition rate as low as 1.2 MHz in a strong normal dispersion regime. The laser was mode locked via spectral filtering. It generated a pulse with large and linear chirp that can be dechirped to 430 fs outside the cavity.
    IEEE Photonics Technology Letters 11/2010; · 2.04 Impact Factor
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    ABSTRACT: In this paper, we report experimental results of measuring picosecond laser pulses using a second-harmonic generation (SHG) intensity autocorrelator. This home-made apparatus of the intensity autocorrelation is an attempt to measure the SHG pulse's intensity change with time. It is clear that an intensity autocorrelation can be used for measuring the pulse length of the ultrashort pulses laser. Using this SHG intensity autocorrelator, we measured the pulse length of a diodepumped picosecond passively mode-locked Yb:SSO laser which emits at a central wavelength of 1061nm at a repetition rate of 52MHz, and a mode-locked picosecond laser amplified system centered on 1064nm at a pulse repetition frequency of 1K HZ. Compared with the commercial autocorrelator, this setup has a larger measurement range, higher accuracy, and more reliable results. In addition, using a high resolution spectrum instrument the apparatus becomes a FROG. The full information of the pulse can be retrieved by using a frequency-resolved optical grating (FROG) algorithm. This setup should be very useful for further optimization of the diode pumped picosecond laser.
    Proc SPIE 11/2010;
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    ABSTRACT: We present a femtosecond off-axis digital holography for investigating the dynamic reversible surface change of a metal film induced by femtosecond laser pulses with fluences near the ablation threshold. A reflection Michelson interferometer (RMI) and a transmission Mach–Zehnder interferometer (TMZI) are integrated in the same setup for recording digital holograms. The RMI is used to measure the laser-induced surface deformation of the metal film, while the TMZI is used to analyze the refraction index change of the metal film induced by the femtosecond laser pulses. Experimental results show that both surface modification and refraction index change of chromium metal film can be observed when femtosecond laser pulses are below and above the ablation threshold. Based on the experimental results, the physical processes of the metal induced by femtosecond laser pulses are given qualitatively.
    Applied Optics 01/2010; 49(13). · 1.69 Impact Factor
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    ABSTRACT: A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal. With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457 nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the output power is better than 1.2% for 8 h continuously working.
    Optoelectronics Letters 01/2008; 4(4):269-272.
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    ABSTRACT: An optical fiber bundle array coupling module with high output power is proposed. The device integrates the coupling technique of the high power laser diode array (LDA) and the flat end-surfaces of fiber array. This module can efficiently couple the output laser of the LDA into the 19-fiber array through the flat-end surface. The fibers are ordinally fixed precisely on the V-grooves, and the fiber array has the same arrange period with the semiconductor laser units of LDA. A cylindrical fiber lens is fixed at the front of the LDA, which will greatly reduce the divergence of the laser beam and assure the laser beam to totally pass through into the end surface of fibers. High output power of 33.2 W of the fiber optic coupling of LDA is achieved, and maximal coupling efficiency is 84%.
    Chinese Optics Letters 05/2007; 5(101). · 1.07 Impact Factor
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    ABSTRACT: In order to get stable continuous wave (CW) mode-locked (ML) laser, conventionally, the laser cavity was designed to reach very small mode radius in the laser crystal to make the laser material saturated. While for the laser diode (LD) end pumped Nd:YVO4 without fiber coupling transmission, as long as choosing the appropriate short focus lens and making the focus area in front of the Nd:YVO4 small enough, we found even large cavity mode volume can make the laser material saturated. In addition, relatively large cavity mode volume can make high power output with single mode come true. Ideal beam quality without high order transverse mode oscillating, the CW ML state turned to be very stable. Accordingly, relatively large mode volume in the laser crystal was designed with semiconductor saturated absorber mirror (SESAM), over 1.5-W CW ML output with near diffraction limited was acquired. The optical-to-optical conversion efficiency reached 30%.
    Chinese Optics Letters 05/2007; 5(101):S42-S43. · 1.07 Impact Factor
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    ABSTRACT: In order to get high efficiency and high brightness laser output with single fiber coupled laser diode array, two laser diode array bars which have 40-W continuous wave (CW) output power at 980-nm wavelength are used in the experiment. The laser diode bars are collimated by two pieces of cylindrical micro lenses in the fast axis direction, and in the slow axis direction step mirrors are used to divide the beams of light to shape the output beam symmetrically. A piece of polarizing beam splitter cube is used to combine the two shaped beams. The focused output beam is coupled into a multimode fiber. More than 55-W output power is obtained from the fiber with core diameter of 400 microns and numerical aperture of 0.22, the total coupling efficiency is about 70% and the brightness is up to 10^(9) level.
    Chinese Optics Letters 05/2007; 5(101):S53-S55. · 1.07 Impact Factor
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    ABSTRACT: Considering laser medium thermal lens effect and thermal focal length changes with pumping power, conventionally, lasers are designed to operate in the middle of thermal stable zones, where the fundamental mode size is insensitive to thermal perturbation, while this method seems impossible when large fundamental mode size is required. Through self-select mode cavity, lasers are designed to work at the border of stable zone instead, where large fundamental mode size in gain media can be reached. With increase of pumping power and self-aperture mode-selective effect, mode size would grow up automatically to a certain value suitable for monomode resonance. With double 180 W pump modules, acoustic Q-switch and LBO external frequency-doubled, over 28 W which M2 equals 4.5 quasi-CW output green laser and 52W 1.064 um IR output is obtained simultaneity. With the insertion or not of the harmonic separator by footswitch high beam quality green IR, and green & IR lasers are obtained conveniently.
    Proc SPIE 12/2005;
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    ABSTRACT: The theory of laser cutter and the technology neck is analyzed. We can conclude that it is almost impossible to deal with the waste thick silicon wafers which are yielded in producing silicon wafers by conventional eroding or diamond cutting, while it is also unperfected with ecumenical laser cutter without good beam quality or precise laser and optics system. It is represented that high average power and high repetition rate laser with good beam quality and precise laser and optics system are pivotal to obtain excellent cutting effect such as thick groove depth, rapid cutting speed, fine kerf section without considering the effect of technique. Considering laser medium thermal lens effect and thermal focal length changing with pumping power, using plano-convex high reflectivity mirror as the back cavity mirror to compensate the heat lens influence, alambda/4 waveplate to compensate heat-induced birefraction, utilize the Nd:YAG self-aperture effect, more than 50 W average power 1.064 um IR output is obtained with beam quality factor (M2) equals 3.19. Through the LD-Pumped Nd:YAG laser cutter we developed with short focus length negative spherical aberration focusing lens, double axis linear step motor positioning system, suitable beam expander multiplying factor, appropriate diameter of exit beam aperture, proper repetition rate, when the cutting velocity equals 400mm/min, 0.75mm thick silicon wafer can be penetrated; when the cutting velocity equals 100mm/min, double-layer 0.75mm thick silicon wafer can be penetrated. The cross section is fine and the groove is narrow, the cutting quality meets the expecting demand.
    Proc SPIE 12/2005;
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    ABSTRACT: An all-fiber high-energy nonlinear chirped-pulse amplification system with two-stage double-cladding fiber amplifiers is presented in this paper. It generates pulses with the energy up to 10 μJ at 20 kHz repetition rate and total accumulated nonlinear phase shift as large as 12.8π. The pulses can be compressed to 137 fs with the compensation of mismatched third-order dispersion by self-phase modulation in the fiber amplifiers.
    Laser Physics 21(11). · 2.55 Impact Factor
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    ABSTRACT: A powerful and stable LD end pumped Nd:YVO4 passively mode-locking oscillator by SESAM was demonstrated. At the pumping power of 30 W, 7 W output was obtained with repetition rate of 79.5 MHz and pulse duration of 15 ps. The beam quality factors M 2 were measured to be 1.30 and 1.33, respectively.
    Laser Physics 22(2). · 2.55 Impact Factor

Publication Stats

15 Citations
22.37 Total Impact Points

Institutions

  • 2011–2013
    • Northeast Institute of Geography and Agroecology
      • Academy of Opto-Electronics (AOE)
      Peping, Beijing, China
  • 2012
    • Chinese Academy of Sciences
      Peping, Beijing, China
  • 2010
    • Peking University
      • State Key Laboratory on Advanced Optical Communication Systems and Networks
      Beijing, Beijing Shi, China
  • 2008
    • Changchun Institute of Optics, Fine Mechanics and Physics
      Hsin-ching, Jilin Sheng, China