Laser polishes silica micro-optic components

Although much research has been performed on the use of carbon-dioxide (CO2) lasers for polishing glass and fused-­silica bulk optics, researchers in the Department of Physics at Heriot-Watt University (Edinburgh, Scotland) have demonstrated, for what they believe to be the first time, efficient surface polishing of fused-silica micro-optic components.

Well-controlled pulses from a planar waveguide CO2 laser with wavelength of 10.59 µm-guided by an x-y translation stage-are delivered to the optical surface in two phases: a preheating pulse, followed by a train of pulses with an adjustable duty cycle over the remaining pulse length. The preheating pulse provides a laser-induced surface-­temperature increase to soften the silica surface and avoid surface cracking and a loss of material by evaporation as the subsequent polishing pulses are delivered. Optimization of pulse delivery yields polished micro-optic fused-silica surfaces with a surface-roughness period of 10 µm or less and an amplitude of approximately 1 µm. In related work, the researchers have also developed a laser-machining technique for the fabrication of custom micro-optic elements. Contact Krzysztof Nowak at k.m.nowak@hw.ac.uk.