Spectral narrowing of a long-wavelength VCSEL using a fiber Bragg grating and wavelength-division multiplexing

垂直腔面发射激光器（VCSEL）是一种从半导体衬底垂直发射光的激光器。输出光束是圆形的，因此适合与光纤耦合。此外，许多器件可以二维排列，适合于光平行传输。vcsel的波长被限制在800纳米波段。然而，这些波长并不适合高速大容量光纤传输。最近，1300或1550纳米波段的vcsel已被开发出来，并于去年投入商用。这些长波长vcsel适用于高速大容量传输。然而，长波长vcsel的光谱变窄尚未实现。在本研究中，我们将光纤布拉格光栅与长波长VCSEL耦合，并证明了光谱变窄。2004年，我们使用了传统的800 nm vcsel，并演示了包括没有透镜的直接耦合在内的光谱变窄。2005年，我们获得了振荡波长为1310nm的长波长VCSEL二极管（Ray Can）。我们在单模光纤中制作了一个反射率为47%的光纤布拉格光栅，并与VCSEL耦合。实验结果表明，当光栅温度为50℃时，不使用光纤光栅时，光谱宽度为85 pm，使用光纤光栅后，光谱宽度减小到64 pm。这表明，波长选择由光纤光栅作为外腔。从85 pm到64 pm，光谱半宽的最大降幅为25%。数据传输特性将被研究。研究了含氢光纤布拉格光栅的制备工艺。加氢对于光栅的制作是必不可少的。通过有限元分析和长周期光栅的制作实验研究了氢在玻璃纤维中的扩散。

A vertical-cavity surface-emitting laser (VCSEL) is a laser that emits light vertically from the semiconductor substrate. The output beam is circular and therefore suitable for coupling with optical fibers. Also, it is possible to arrange many devices two-dimensionally, which is suitable for parallel optical transmission. The wavelengths of VCSELs have been limited to the 800-nm band. However, these wavelengths are not suitable for high-speed large-capacity optical fiber transmission. Recently, VCSELs in the 1300 or 1550 nm band have been developed, and become commercially available last year. These long wavelength VCSELs are suitable for high-speed large-capacity transmission. However, spectral narrowing of long-wavelength VCSELs has not been performed.In the present study, we have coupled a fiber Bragg gratings with a long wavelength VCSEL and demonstrated the spectral narrowing. In 2004, we used conventional 800-nm VCSELs and demonstrated spectral narrowing including direct coupling without a lens. In 2005, we obtained the long-wavelength VCSEL diode (Ray Can) with 1310-nm oscillation wavelength. We fabricated a fiber Bragg grating in singlemode fiber with a reflectivity of 47%, and coupled with the VCSEL. As a result of the experiment, when the grating temperature was 50℃, the spectral width without using an FBG was 85 pm FWHM, then the spectral width decreased to 64 pm by using an FBG. This shows that wavelength selection by the FBG as an external cavity. The achieved maximum reduction in the spectral halfwidth was 25% of that from 85 pm to 64 pm. Data transmission characteristics are to be investigated.We also studied the fabrication process of fiber Bragg grating related with hydrogen. Hydrogen loading is indispensable for grating fabrication. We studied the diffusion of hydrogen in the fiber glass by the finite-element-method analysis and by fabrication of long-period gratings experimentally.