利用1．313μm激光泵浦掺铒石英光纤产生上转换放大自发辐射

报道了利用１．３１３μｍ波长调Ｑ锁模Ｎｄ３＋：ＹＬＦ激光泵浦国产掺铒石英光纤同时产生可见光４６３ｎｍ（４６３ｎｍ，４７５ｎｍ，４８５ｎｍ，４９４ｎｍ，５０１ｎｍ，５１０ｎｍ），５２５ｎｍ，５４０ｎｍ（５２５～５６４ｎｍ），二次谐波信号６５６ｎｍ（６５６～６７５ｎｍ）和近红外８０４ｎｍ（７８４～８２０ｎｍ）等波段放大自发辐射的实验结果．在可见光４６３ｎｍ波段，在高泵浦功率下观察到随泵浦光功率增大，邻近几个中心波长与４６３ｎｍ波长信号产生类似级联共振放大增强的现象。同时发现几个中心波长辐射光谱宽度随泵浦光功率增加有加宽的关系，这与现有实验结果报道不一致。实验中还发现３ｍ长光纤与４．５ｍ长光纤在输出可见光自发辐射光谱方面有很大的不同．３ｍ光纤在相等泵浦光功率下．出现邻近波长共振放大加强的几率比４．５ｍ光纤小得多。根据能级跃迁关系提出了共振四光子吸收将基态４Ｉ１５／２离子抽运到高能态２Ｇ７／２，然后跃迁辐射回到４Ｉ１３／２态的机制，给出了实验结果的初步机理解释。

Amplified Spontaneous Emission Generation of Wavelength Upconversion in a Er3+-doped Silicate Single-mode Optical Fiber Pumped at 1. 313 μm

We report the observation of amplified spontaneous emission (ASE) in the visible light range in silica-based single-mode optical fibers doped with Er 3+ (Er3+/Al2O3/GeO2/Sio2). Frequency-upconverted emissions were observed simultaneously in a number of visible wavelengths around 463 nm (463 nm , 475 nm , 485 nm , 494 nm , 501 nm and 510 nm), 525 nm and 540 nm (525 nm, 540 nm, 547 nm, 552 nm and 565 nm),around the second harmonic signal wavelength 656 nm (656 nm, 663 nm, 669 nm and 675 nm) and near-infrared lines (782 nm, 802 nm, 809 nm and 823 nm) when the fibers were pumped by a mode-locked, Q-switched Nd3+"YLF laser operating at 1.313 μm. We have observed an interesting phenomenon that the emission spectrum around 463 nm band likely has a cascade amplification enhancement characteristic when the fiber is reported for the first time. The nonpolarization-preserving Er3+-doped single mode fiber used in our experiment had a 6 μm diameter core and a 0.979 μm cutoff wavelength. The NA is 0.235. The Er3+ dopping level is about 500×10 -6. he fiber lengths used were 4.5 m and 3 m separately. The laser power coupled into the fiber is about several hundred milliwatts. The pump mechanism for around 463 nm is that in the first step resonant two photon absorption process the ions are excited to the 4F9/2 level from the 4I15/2 ground state, and a second resonant two photon transition connects ions', 4I9/2 state to the 2G7/2 excited state, giving rise to amplified spontaneous emissions from 2G9/2~11/2 to 4I13/2.