Fabrication of IR microlens using a fiber laser

Abstract

In two subsequent stages, various types of silicon microlenses were fabricated. A fiber laser of 1.06 µm was employed to ablate micro dips at the silicon surface and then a mixed acid solution was used to etch the wafer ultrasonically. The experimental data demonstrate spherical, cylindrical IR microlenses and IR microlens array formation with an optimum numerical aperture of 2.39 minimum microlens height of 21 μm, diameter of 32 μm and focal length of 6.7 μm with maximum resolution of 0.395 μm and magnification of (44X) was achieved. The minimum experimentally achieved microlens’ roughness was 45 nm. Theoretical calculations were conducted to estimate the temperature at the silicon surface during the ablation stage. A temperature of approximately 3590 K is established at the center of the laser-silicon in the ablation stage. Due to the controllable laser micromachining process, optoelectronics and biological imaging are viable applications for IR microlens arrays.