In the paper, a 45 degree TFBG was fabricated in photosensitive fiber successfully using phase mask technique. The polarization-dependent loss characteristic of the TFBG was experimentally researched in the paper using a special measurement system. The measurement results showed that the 45 degree TFBG could act as a polarization possession element. Based on the 45 degree TFBG, a linearly-polarized Yb-doped fiber laser was demonstrated. The polarization-extinction ratio of the output laser is about 30 dB. The output power was about 13 mW with the pump power of 100 mW. The central wavelength of the laser is 1064nm and the wavelength bandwidth was about 0.7nm. Being a polarization device, the TFBG has the advantages of in-fiber, compact, good polarization capability and low price.
A 974 nm laser diode(LD) pumped 1120 nm ytterbium(Yb)-doped fiber laser has been experimentally demonstrated, which will be subsequently used to pump 1178 nm Raman fiber laser based on stimulated Raman scattering(SRS) effect. The resonator composes a normal single-mode Yb-doped fiber and a pair of fiber Bragg gratings(FBG). The maximum output power of 8.4 mW is achieved when the launched pump power is 183.7 mW with an optical-to-optical conversion efficiency of 4.6 %. The central wavelength is 1120.93 nm with a linewidth as narrow as 0.02 nm.
Numerical experiments are carried out about the temporal and spatial variation of branch points by four-dimension code of laser propagating in atmosphere. The theory of branch-point detection and phase reconstruction is introduced. The act of branch points' creating and annihilating is emulated when the light wave propagating in atmosphere. The evolvement of branch points in some propagating range with time is emulated, too. The behavior of branch points in the distorted optical field is simulated when the main laser and beacon laser propagate in the atmosphere with opposite direction at the same time. The work could provide a reference for further study of laser propagation through atmosphere and adaptive optics system.
A highly efficient TEM<sub>00</sub> mode 1063 nm Nd:GdVO<sub>4</sub> laser is accomplished with a simple plano-plano resonator. The laser threshold pump power is 856 mW. The maximum laser power of 2.05W is achieved when the pump power is 3.76 W, corresponding to a slope-efficiency of 70% to absorbed pump power. The quality of the output beam is analyzed with a laser beam quality analyzer. The perfect laser beam quality is partially attributed to the short cavity length of 11 mm and the precise temperature control to the Nd:GdVO<sub>4</sub> crystal. The output laser central wavelength is 1063.1 nm with a laser linewidth of 0.06 nm.
In this paper, a pulse stretcher based on multilayer volume holographic gratings(MVHG) is shown. The diffraction
properties of the pulse stretcher under ultrashort pulse are investigated based on the modified multilayer coupled wave
theory. The spectral intensity distributions of the diffracted beam are calculated. The diffraction bandwidth, pulse
duration, pulse expansion and the total diffraction efficiency of the pulse stretcher are also analyzed. The pulse
broadening is accomplished by adjusting the width of the intermediate layer of a system of MVHG. The calculation
results show that using this new pulse stretcher system to broaden pulse has many advantages: the efficiency of
diffraction is high, the structure of stretcher is adjustable to vary the amount of temporal broadening of the light pulse,
and the structure is also more compact than alternative approaches.
The optimum parameters' expressions of the lens duct are theoretically deduced with the help of numerical analysis of
ray tracing. Based on the theoretical analysis, we simulated the rays' transmission trace in the duct and calculated the
intensity distribution of the output beam. The influence of the parameter's value on coupling efficiency is also analyzed
in the paper. With the optimum parameters lens duct, we implemented the coupling experiment. A smooth and
symmetric beam with high quality is obtained. The coupling efficiency of the lens duct is larger than 91%. The
experimental results agree well with the theoretical analysis. More important, the duct's coupling efficiency is better
than the results reported previously.
A passive Q-switched Yb-doped microstructure fiber (MF) laser is demonstrated using a GaAs wafer as the saturable
absorber. A high Ytterbium-doped fiber with a core diameter of 21 μm and a numerical aperture of 0.04 was used as the
active fiber. The large-diameter core allows for greater energy storage than conventional single-mode core designs and
the small NA of the core ensures the good beam quality of the laser. A pulse duration as short as 80 ns was obtained with
the maximum repetition rate of 830 Hz. The maximum average output power is 5.8 W at 1080 nm wavelength.
A passively Q-switched pulse-LDA (laser diode array)-pumped Nd:YVO<sub>4</sub> laser using As<sup>+</sup> implanted GaAs as the saturable absorber is demonstrated. In the experiment, a Q-switching pulse width 7ns with a pulse energy 23.5μJ is achieved which, to our knowledge, is the shortest pulse width in a passively Q-switched Nd:YVO<sub>4</sub> laser using GaAs as saturable absorber. The laser emits only one Q-switching pulse during each pump-pulse time with a Q-switching efficiency of 26.8%. We also investigate the characteristics of the Q-switched pulse by adjusting the pumping pulse energy, pulse width and pulse repetition rate respectively. The experimental results are discussed as well in the paper.
A passively Q-switched pulse-LDA(laser-diode-array)-pumped Nd:YVO4 laser using As<sup>+</sup>ion-implanted GaAs as a saturable absorber is demonstrated. In the Q-switching experiment, the laser produces one Q-switching pulse in every pumping pulse duration and a Q-switching pulse width 7 ns is achieved. When the pumping power is increased a Q-switched mode-locked laser is achieved. Using a 60% initial transmission GaAs wafer, the modulation depth of larger than 95% is obtained. The repetition rate of the mode-locked pulses in the Q-switched envelope is 991MHz. The effects of the pumping pulse energy, pumping pulse width and repetition rate on the characteristics of the Q-switched mode-locked pulses are also investigated respectively. The experimental results are discussed as well in the paper.
6.5 mol.% MgO-doped LiNbO<sub>3</sub> (MgLN) single crystal has been grown by the Czochralski technique. The MgO-doped crystal shows a shift in the absorption edge towards shorter wavelengths and a three orders of magnitude increase in the photorefractive damage resistance compared to the congruent LiNbO<sub>3</sub> crystal (CLN). This material has been periodically poled (PP) at room temperature by applying electric field, and the coercive field is 5 KV/mm, which is about 1/4 of that for congruent LiNbO<sub>3</sub>. Periodic poling of 1 mm thick 6.5 mol.% MgO-doped LiNbO<sub>3</sub> substrates has been successfully performed and its operation in a femtosecond second-harmonic generation at room temperature. The performance of quasi-phase-matched second harmonic generation with a 1mm thick PP MgO:LN was compared with that of the second harmonic generation with the PP CLN at room temperature. The PP MgO:LN exhibited better performance.