Dynamic properties measurement of vibrating microprobe for nano-position sensing using radiation pressure control

We demonstrate the dynamic properties of the optically vibrated microsphere for establishing a position detection probe for the nano-CMM. The principle of the position detection probe is based on the single-beam gradient-force optical trap of a micrometer size probe sphere and the vibration probing technique. An optically trapped microsphere in air is forced to vibrate in the transverse direction using the oscillating Nd: YAG laser beam. By studying the frequency response of the optically vibrated microsphere using PSD, the dynamic properties such as spring constants in the different directions are evaluated. Both numerical and experimental analyses are performed to investigate the relation between a viscous drag coefficient and a distance from a surface of a specimen to be measured. Based on the obtained information, a novel principle of position sensing using the phase delay response due to drastically increasing viscous drag coefficients near the surface is proposed. Fundamental measurement of the phase delay is demonstrated by probing the edge of an as-cleaved silicon wafer in the lateral direction. The measurement results suggest that the proposed method is valid for sensing a position with the resolution of nanometer order.