Single-ste¥laser process fabricates refractive microlenses

Focusing a CW argon-ion laser beam onto semiconductor-doped glass results in the controlled formation of a refractive microlens on to¥of a commercially available packaged diode laser. According to researcher Nabil Lawandy of Brown University (Providence, RI) this simple method may be a cost-effective alternative to current multiste¥microlens-fabrication processes, which typically involve photolithography and/or ion-implantation steps. Semiconductor-doped glasses are sold commercially as

Single-ste¥laser process fabricates refractive microlenses

Focusing a CW argon-ion laser beam onto semiconductor-doped glass results in the controlled formation of a refractive microlens on to¥of a commercially available packaged diode laser. According to researcher Nabil Lawandy of Brown University (Providence, RI) this simple method may be a cost-effective alternative to current multiste¥microlens-fabrication processes, which typically involve photolithography and/or ion-implantation steps. Semiconductor-doped glasses are sold commercially as long-pass filters; these materials are borosilicate glass uniformly impregnated with nanometer-sized crystals of semiconductors.

Above-bandga¥light focused to a sufficiently small radius with an adequately high intensity is necessary to fabricate a microlens. The microlens is then usable at wavelengths longer than the bandga¥of the chosen semiconductor-doped glass. Varying diameter or intensity of the laser beam creates lenses with diameters ranging from 3 µm to the upper limit, which is determined by available laser power. The simple model proposed for this process is one in which laser irradiation causes the glass material to melt and solidify. Because molten glass has a lower density than solid glass, the extra volume swells u¥from the substrate and resolidifies to form a microlens.

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