你什么也没看见?

一天下午,阿布纳在小区里散步。他头戴尖顶帽,正沿着小路走出一片小小的棕榈和椰子树林的时候,听见后面吵吵嚷嚷跑来一群人。这是一群小学生,有的人手里还拿着纸和笔。一位戴眼镜的小男孩看来是认识阿布纳的,他彬彬有礼地向阿布纳问好。阿布纳好奇地问:“你们这是干吗?要到哪儿去?”“我们到处走走。”小男孩笑得很勉强,向阿布纳挥挥手,去追赶同伴们了。“到处走走?”阿布纳更疑惑了。他几乎天天在这个时候散步,可从来没遇见过一群小学生啊———这个时候他们应当在学校里上课才对。阿布纳是好奇心很强的人,从来都不愿放过任何一个自己没弄…     

Er^3＋-Yb^3＋ Co-Doped Fiber Ring and Line Laser

Er^3 -Yb^3 co-doped fiber of 2 m long is used as the laser gain medium. Two fiber lasers with different structures have been set up, one is the line cavity fiber laser with the dielectric mirror being replaced by an all-fiber reflecting mirror,the other is the ring cavity all-fiber laser. Both set-ups have achieved lasing operation at the wavelength of 1.53 μm. Pumped by the 1 064 nm light from all-solid-state Nd : YAG laser, the two fiber lasers at 1 530 nm are operational. Their output powers are 7.8 mW and 2 mW with 130 mW and 160 mW pump powers.