Fabrication of IR Microlens Using Fiber Laser

Various types of silicon micro lenses were fabricated by two subsequent stages. Fiber laser of 1.06 µm was employed to ablate micro dips at the silicon surface then a mixed acid solution was used to ultrasonically etch the wafer. 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 (X 44) was achieved. The minimum experimentally achieved micro lens’s roughness was 45 nm. Theoretical calculations were conducted to estimate the temperature at the silicon surface during the ablation stage. 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.