The Coupling Research Of 980nm Pumping Laser And Other Semiconductor Lasers With Lensed Fibers

With the rapid development of high speed and high capacity fiber communication and optoelectronic components,the coupling efficiency of laser diode (LD) and single mode fiber (SMF) has become the most fundamental problem for engineers and researchers to solve. Coupling efficiency not only affects fiber communication relay distance,but also affects the performance of EDFA and semiconductor light amplifier (SLA). So it is very important to improve coupling efficiency and reduce its cost.According coupling theory,the coupling of laser diode to single mode fiber is to meet the mode field diameter match and the phase match. For the technology of butting laser to a fiber,the coupling efficiency is very low for the serious phase mismatch and mold field diameter mismatch. So it is necessary to minimize the mismatch. Recently,various coupling techniques have been used to achieve a low-loss coupling between a semiconductor laser and a single mold fiber. The experimental results in these studies have been reported for lasers with either circular or near circular (elliptical ratio close to 1) beam profiles. However,InGaAs strained-layer single quantum well lasers,optimized for low threshold current and low series resistance,have a highly elliptical beam structureemanating from the laser facet. Therefore,for 980nm pumping,a significant disadvantage is the low coupling efficiency to the single mode fiber because of the mold field mismatch between the elliptical laser beam and the circularly symmetrical fiber mode and also because of the phase mismatch.A theoretical and experimental study of a new,efficient technique to couple a laser,emitting a highly elliptical beam,to a single-mode fiber without the use of bulk optical components is presented. The technique involves butt coupling the laser to a cylindrical lensed fiber and spherical lensed fiber. Such lensed fiber endfaces correct for the phase front mismatch between the curved laser beam wave front and the planar fiber beam. A theoretical formula for the coupling efficiency in the absence of both angular and transverse misalignments and a theoretical formula,which involves both angular and transverse misalignments,are derived. In the experiments,experiments about 980nm pump laser and cylindrical lensed fiber coupling have been done. In order to broaden the application,some experiments about the coupling of 1310 nm laser and 1550 nm laser with spherical lensed fiber have been done. Comparisons indicate that theoretical results are in good agreement with the experimental results.Finally the paper summarizes the work,which have been done and provide some ways to optimize the mode. What is more,the paper brings forward some research directions,which are deserved to deep study.