Multi-transverse-mode competition, coupling induced instabilities and multi-pulse or satellite pulse oscillations were investigated experimentally and theoretically in laser-diode-pumped Cr,Nd:YAG self-Q-switched microchip lasers under large pump beam diameter. The different transverse modes have great effects on the laser pulse temporal characteristics such as pulse profile, pulse width, instability of peak power and repetition rate jitter. Multi-transverse-mode, multi-pulse oscillation and periodical pulsation were observed by varying the pump beam diameter.The effect of transverse modes on the instability and multi-pulse oscillation were studied by modified coupled rate equations by taking into account the transverse-mode competition of inversion population under different pump conditions. The numerically simulated results are in good agreement with the experimental results. These results show that the multi-pulse oscillation and instability in the pulse train were attributed to different transverse mode coupling and competition. The peak power instabilities and pulse repetition rate jitter of the laser pulses due to transverse mode coupling were also investigated.

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Exploiting a piece of 0.2 m long Tm-Ho codoped fiber as the saturable absorber, we demonstrate a wideband wavelength tunable passively Q-switched Er-doped fiber laser. The Tm-Ho codoped fiber has a wide absorption band around 1550 nm, promising wideband Q-switching of Er-doped fiber lasers. With a Fabry-Perot tunable filter, stable passive Q-switching is observed in a wide wavelength range from 1535 to 1573 nm. The repetition rate of the laser system is tunable with both the pump power and the lasing wavelength in the range between 0.5 and 50 kHz.

Determination of parameters is presented in the modeling of Tm-doped fiber lasers. The thesis chooses parameters, numerical simulation to examine the performance of the laser system for different pump schemes and cavity parameters. Their impacts on the laser performance are discussed.

Discovering disease-gene association is a fundamental and critical biomedical task, which assists biologists and physicians to discover pathogenic mechanism of syndromes. With various clinical biomarkers measuring the similarities among genes and disease phenotypes, network-based semi-supervised learning (NSSL) has been commonly utilized by these studies to address this classimbalanced large-scale data issue. However, most existing NSSL approaches are based on linear models and suffer from two major limitations: 1) They implicitly consider a local-structure representation for each candidate; 2) They are unable to capture nonlinear associations between diseases and genes. In this paper, we propose a new framework for disease-gene association task by combining Graph Convolutional Network (GCN) and matrix factorization, named GCN-MF. With the help of GCN, we could capture nonlinear interactions and exploit measured similarities. Moreover, we define a margin control loss function to reduce the effect of sparsity. Empirical results demonstrate that the proposed deep learning algorithm outperforms all other state-of-the-art methods on most of metrics. CCS CONCEPTS • Computing methodologies → Semantic networks.

A theoretical model concerning the Tm-Ho codoped fiber saturable absorber based passive Q-switching of an Er-doped fiber laser is established. Comparison with the Tm-doped fiber saturable absorber is described and discussed. Numerical results indicate that, compared with a Tm-doped fiber saturable absorber, the Tm-Ho codoped fiber saturable absorber shortens the lifetime of the 3 F 4 energy level and improves the operation of the laser system.

Mode-locking operation of an Er-doped fiber laser with a Tm–Ho co-doped fiber saturable absorber is demonstrated for the first time. Q-switching, Q-switched mode-locking and CW mode-locking operation modes are observed sequentially with increase of the pump power. In the mode-locking operation mode, a repetition rate at the fundamental cavity frequency of 9.05 MHz is obtained with a pulse duration of 46.3 ns. By rotating the polarization controller, a repetition rate up to 887 MHz is achieved, and the pulse duration is shortened to 0.548 ns.