Lianju Shang

An efficient shooting method for fibre Raman amplifier design

A powerful shooting algorithm, which is the combination of the simple shooting method and the modified Newton method, dedicated to fibre Raman amplifier (FRA) design is proposed and numerically demonstrated for the first time, to the best of our knowledge. An effective initial-guess-providing scheme for the shooting method has also been proposed. The interactions among the pumps, signals, forward and backward amplified spontaneous emission, and co- and counter-propagating Rayleigh scattering components have all been taken into account in the theoretical model used by the proposed method. Studies in comparison with previously proposed methods show that the proposed new method is faster and more robust than the previously proposed ones. This new method can be used in the gain and noise performance design of FRAs with various kinds of geometries including forward pumping, backward pumping, or bi-directional pumping.

Overlap integral in integrated acousto-optic devices

The overlap integral of guided acousto-optic interaction is investigated theoretically. The overlap integral of YZ-LiNbO3 (Y-cut crystal, Z-propagating surface acoustic wave) is discussed with different penetration depths for TE- and TM-polarized light. Some valuable results are obtained for the design of acousto-optic devices.

Theoretical analysis and design of non-collinear guided-wave acousto-optic devices

A numerical analysis is presented about the performance of non-collinear acousto-optic interaction in LiNbO3 guiding structures. To get the optimal design for a higher diffraction, the SAW power required for 100% diffraction (P 100) dependences on the length of acousto-optic (AO) interactions, guided optical mode, waveguide depth and driving frequency are investigated. Some valuable results are obtained for design of guided-wave acousto-optic devices.

FACTORS THAT INFLUENCE PEAK POWER OF Q-SWITCHED FIBER LASER

Q-switched fiber lasers are very attractive sources in many applications such as military affairs, surgical operation, laser machining, laser marking, nonlinear frequency conversion, range finding, remote sensing and optical time domain reflectometer. To improve the peak power of Q-switched fiber laser is what we pursue, and to know the factors that influence the peak power is what we should make clear first. In this paper, certain essential factors that influence the peak power are presented, with their theoretical basis clarified, which may be helpful to the design of the kindred Q-switched fiber lasers.

Overlap Integral in Abnormal Guided Acousto-Optic Interaction

A computer model of overlap integral is presented in abnormal guided acoustooptic interaction using mode conversion. Overlap integral of LiNbO3 is analyzed for TE↔TM polarized light in abnormal acoustooptic interaction with different penetration depths. Some valuable results are obtained for design of acoustooptic devices.

NOVEL METHODS TO IMPROVE PULSE ENERGY OF Q-SWITCHED FIBER LASER

Q-switched fiber lasers are very attractive sources in many applications such as in military affairs, surgical operation, laser machining, laser marking, nonlinear frequency conversion, range finding, remote sensing and optical time domain reflectometer. Our goal is to improve the pulse energy of a Q-switched fiber laser. In this paper, certain feasible methods to improve the pulse energy are presented, with their theoretical basis clarified, which may be helpful for the design of kindred Q-switched fiber lasers.

Study of doughnut beam with high charge number generated by liquid crystal plates

The doughnut beams with charges of 1 to 3 are generated by one and stacking two and three Liquid crystal(LC) spiral phase plates with cell gaps of 7 μm respectively. Theoretically, any charge number can be obtained by the stacking method. High efficiency and flexibility are the advantages of generating doughnut beams by stacking liquid crystal spiral phase plates. The interference of doughnut beam generated by LC spiral phase plate and plane wave has been studied. The numerical simulation results agree with the experiment.

Design of biconical waveguide in integrated acousto-optic modulator

In this paper, a numerical method is presented to design a biconical waveguide. We use this method to calculate the transmitted and radiated power of the biconical waveguide in an integrated acousto-optic modulator, then we plot the normalized power loss curves versus the taper length and get the optimum design.

An analysis of designing a CW double-clad fiber laser

In this paper the parameters of a CW double-clad fiber laser are theoretically analyzed, which is of important references to designing the kindred double-clad fiber lasers. This paper also offers a personalizing design scheme of double-clad fiber lasers, with the influence of some important parameters on the output power clarified.

Efficient shooting algorithm for Raman amplifier equations

An efficient shooting algorithm based on the simple-shooting method and the modified Newton-method for fiber Raman amplifier design is proposed. By introducing the Broydens rank-one method, the time-consuming calculation of the Jacobian matrix is dramatically relieved. Numerical simulation results show that the simulation efficiency of the proposed method has been improved more than 70 percent compared with the conventional shooting method.