圆形线电流的磁感应强度

用磁标势法计算了圆形线电流的磁感应强度。利用这个结果证明了圆形线电流平面中心的磁感应强度有极小值,给出了圆环回路的自感系数的计算公式。     

Mechanism and elimination of spectrum filtering in a high power mode-locked fibre laser witha free output coupler

The filtering mechanism of a free output coupler mode-locked laser based on large-mode-area photonic-crystal fibre is analysed. A filtering-soliton mode-locked laser with 495~fs pulse width and 21 nJ pulse energy is achieved. Another novel cavity configuration is established to eliminate the filtering effect. Pulses, each 457~fs in width and 16.5 nJ in energy, are obtained in a soliton-like regime. Pulses, each 387~fs in width and 15.8 nJ in energy, are also generated in a stretched pulse regime and could be dechirped to 119~fs externally to the cavity.