Studies On Coupling System Composed Of GRIN Rod Lenses For Double-cladding Planar Waveguides

The work of this dissertation is supported by National Science Fund Council of China under the program of– Research of Double-Cladding waveguide Lasers Using Direct Bonding Technique (No. 60578022).Recently, high-power LD-Bars as an ideal kind of pumping light sources have been developed very rapidly, which efficiency of electrisity to light is approaching 70% and the average cost per watt is declined to $25. Meanwhile, the various optical waveguide fabrication methods, expecially double-cladding fiber which is suitable for LD pumping, have been invented successfully. Double-cladding planar wavguide fabricated by derict-bonding technique, which is not limited by the mismatch of crystal lattices, is more suitable for LD-Bars pumping than optical fiber and could be a promising laser in the future.This thesis focuses on the design and optimization of coupling system for double-cladding planar waveguide laser made by derict-bonding method and pumped by LD-Bars. The main research work and key new ideas of the dissertation are list as follows:1. The features of waveguide laser and LD-Bars are reviewed and the different results of GRIN rod lens and common rod lens are compared. The current status of LD-Bars coupling systems and beam shaping technique are introduced thoroughly.2. The function of ray trace in GRIN rod lens placed along transverse direction is derived from ray equation and it is proved that the ray path does nothing with (central) refractive index of GRIN rod lens in that case. So the fomula of ray path could be concluded basing on the conclusion obtained above.3. The characteristics of GRIN rod lens for collimation or focus are analysed by ray tracing through the Matlab software and by fitting through the Origin software. The parabola function of the ray in a GRIN rod lens is discovered by fitting mothed and a new formula and the way of how to use it, which is quite useful for researching the GRIN rod lens effectively and easily, are concluded independently for the first time for the GRIN rod lens laid along transverse direction.4. A coupling system which a set of GRIN rod lenses laid along transverse direction are used to collimate and focus the light emited from LD-Bars into the double-cladding waveguide laser is designed. Then three parameters of the coupling system are optimized by GA so that a coupling efficiency of 78.7% is permitted from that system in fast axis of LD-Bars. In slow axis, the beams are designed to be cut and shaped by using the stripe mirrors technique which can cut down the size of beam along low axis and fill the gap between bars along the fast axis.