Study On High Efficiency Coupling Properties For Semiconductor Laser Diodes To Optical Fibers

The application fields of high-power semiconductor laser diodes (LDs) are wider and wider due to their unique advantages such as small in size, low power consumption, high electric to optical energy converting efficiency and cheap in cost, which couldn't be competitive by other forms of lasers, results in their more and more important role for society, economics, military and human's daily-life. It is believed that the trend will go on as the development in research and study lever and their future is expected.The coupling issues with optical fibers are often deal with in many application fields of high-power LD, such as the light sources and pumping sources of optical fiber amplifiers in optical fiber communications systems, laser surgery operation in medicine, laser welding and heat processing in materials mechanical process and so on. So the studies on the coupling systems with high efficiency, more practices, high reliability and more economics according to the high-power LDs'characteristics have been one of the interesting research and study dots. To date, they passed through separated single lens, separated combine-lenses and lensed fibers which integrated with optical fibers, total three generations. Lensed fibers are very popular and first choice at present because of their simple structures, high manufacture efficiency and easy integrated packaging properties.The main reason that the coupling efficiency for high-power LDs to optical fibers is not so high is that the difference in mode between them is quite serious. The formers'modes are, normally, asymmetric ellipses, while the latter's'ones are centre-symmetric circles. So the coupling performance between high-power LD and fiber should be improved through both LD and fiber aspects. In LD aspect, reduction or increase of the active region thickness can reduce the aspect ratio of the LD beam and consequently improve the beam's symmetry. There are many approaches to achieve the purpose, and one of the perfect them is tunnel-cascaded multi-active regions large cavity LD structure, in which not only the effective thickness of the active region increase but also obtain LDs'low threshold current and high slope efficiency and other properties.In optical fiber aspect, the incident beam can be collimated, converted and focused by some kinds of lenses, making the mode of incident beam matched with or near the optical fiber's modes.In this thesis, thorough theoretical analyses and experimental investigations were made for the external optical properties of a 980nm high-power tunnel junction regenerated multi-active-region quantum well stripe-geometry AlGaAs/GaAs/InGaAs LD and three different stripe-width 980nm high-power...