Design And Process Research Of The Microlens For Semiconductor Laser Diode Array Collimating

Diode lasers have various applications in the field of photonics. In comparison with solid-state or gas lasers the advantages of diode lasers are their small dimensions, low cost, high output-to-input conversion efficiency, whereas among drawbacks of diode lasers belong an ellipticity, astigmatism, and a strong divergency of an outgoing beam. In recent year, high-power applications for semiconductor laser have been of growing interest. Optical power density and total power are important parameters for laser systems in applications involving coupling of light into optical fibers, pumping solid state lasers including fiber lasers, processing materials and medical procedures. Efficient collimation of such a partially coherent, linearly extended light source with large divergence angles is a non-trivial problem and difficult to achieve with conventional optics. We designed, fabricated, and characterized a micro-optical device with diffractive or refractive optical elements. The main contents of this paper are presented as: (1) Introduce the characteristic of semiconductor laser diode and the traditional way to collimate it. The difficult and the method to resolve it by microlens is presented. (2) The matrix optics base on geometry optics and binary optics base on diffractive theory are researched to design the microlens. (3) A collimating system with two or one aligned microlens elements is designed. The parameters of the microlens are worked out base on the matrix optics and binary optics. (4) Fabrication techniques of microlens especially based on SF6/O2/CHF3 reactive ion etching are developed. Etching rates and selectivity of silicon are investigated by using experimental design and stastical analysis and optimal paramters are obtained. (5) Convex refractive microlens arrays are successfully fabricated by the method composed of heat-forming photoresist and RIE , on BCB materials, and the experimental fabrication parameters are obtained. The point spread function (PSF) of the array is test, and the result of collimation is measured.