Laser diode end-pumped efficient coupling system based on microlens arrays

Efficient pumped coupling is one of the important technologies of diode pumped solid state laser system applying end-pumped structure. This work present a novel pumped coupling optical system based on microlens arrays. In the coupling system, the light of laser diode stack is incident on an imaging microlens array, that cuts the beam into a number of beamlets. Subsequently these beamlets are overlapped in the pumped surface of laser media through an aspheric focusing lens. Then a high homogeneity pump field is realized. Furthermore, for different aspect ratios of the homogenized spot two microlens arrays with crossed cylindrical lenses are used to match different pump field size. Such coupling system was designed by ray tracing method using ZEMAX TM Non-Sequential Components analysis tools. The non-sequential raytracing simulation shows that a 5 × 5 mm 2 Top-Hat intensity pump profile was got at a working distance of 40 mm and the homogeneity of the intensity distribution is better than 90%. In comparison with the traditional coupling optical system homogenization by means of microlens arrays is more flexible and requires a reduced number of optical components.