Jiping Ning

Novel shooting algorithm for highly efficient analysis of fiber Raman amplifiers

An efficient and stable algorithm based on the simple-shooting method to solve the fiber Raman-amplifier (FRA) equations is proposed and numerically demonstrated. In the algorithm, the conventional Newton-Raphson method is substituted by a more efficient and stable modified Newton method to serve as the correction mechanism in the shooting iterations. By introducing the Broydens rank-one method into the modified Newton method, the time-consuming calculation of the Jacobian matrix is dramatically relieved, and the efficiency of the proposed algorithm is further remarkably improved. An effective initial-guess-providing technique for the shooting method has also been proposed. Simulation results show that the efficiency of the proposed algorithm is improved more than three times compared with those of the previously reported methods. This algorithm can be used in the design of various kinds of FRAs to predict their gain and noise performance accurately.

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.

Analysis of integrated acousto-optic modulators fabricated on 128-deg-rotated Y-cut X-propagation LiNbO3

The efficiency of integrated acousto-optic (AO) modulators with different optical penetration depths fabricated on 128-deg-rotated Y-cut X-propagation lithium niobate (128-deg YX-LiNbO3) is analyzed theore- tically for the first time by determining the overlap integral between the optical and acoustic field distribution. The results show that the smaller the optical penetration depth is, the higher the optimum surface-acoustic- wave (SAW) frequency and diffraction efficiency and the larger the band- width will be. Compared with TM-polarized light, TE-polarized light offers better performance for modulation. However, for a well-concentrated opti- cal waveguide, TM-polarized light is attractive for AO modulators, which employ a single SAW.

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.

INFLUENCE OF PUMP DIRECTION IN ALL-OPTICAL GAIN-CLAMPED FIBER RAMAN AMPLIFIER

The influence of pump direction in all-optical gain-clamped fiber Raman amplifier using the directional couplers in feedback loop is demonstrated. The isolator direction decided the lasing direction in feedback loop. The comparison of performance in two lasing directions for both schemes is shown. It is concluded that the forward pumping configuration with forward lasing has better gain clamping performance and noise performance.

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.

SURFACE-ACOUSTIC-WAVE FIELD AND ACOUSTO-OPTIC INTERACTION IN AlN/128-DEG-ROTATED Y-CUT X-PROPAGATION LiNbO3

The efficiency of guided-wave acousto-optic (AO) interaction in AlN/128-deg-rotated Y-cut X-propagation lithium niobate (128-deg YX-LiNbO3) structure is analyzed theoretically for the first time by determining the overlap integral between the optical and the surface acoustic wave (SAW) field distribution. The results show that the use of an AlN film can increase the phase velocity of SAW, the electromechanical coupling coefficient and the diffraction efficiency of AO interaction. A maximum of 9.33% for the electromechanical coupling coefficient is obtained when the normalized thickness of AlN film equals 0.09. The diffraction efficiency has a significant improvement when the normalized thickness of AlN film is increased from 0 to 0.05. And, the improvement for the TM polarization is more evident than that for the TE polarization. However, for a well-concentrated optical waveguide, the use of an AlN film reduces the diffraction efficiency of the TM polarization when the SAW frequency is low.

A new theoretical analysis model about the design of acoustical waveguide in the guided acousto-optic devices

In this paper, we present a new theoretical model for the design of acoustical waveguides in the guided acousto-optic devices. The electromechanical coupling coefficient and the velocity in the acoustical in the acoustical waveguide are analyzed for different waveguide thicknesses. Some valuable results for the design of acousto-optic devices are obtained.