We have found that the astigmatic optical system inside the commercial DVD optical head can simultaneously detect the height and the two-dimensional tilt angle of a surface with a very high sensitivity and a very high speed. No other detection system has been demonstrated with such a capability. An atomic force microscope, using our detection system to sense the deflection of microfabriacted cantilevers, can resolve single atomic steps on graphite surfaces with the noise level less than 0.04 nm in the topographic images, equivalent to those of the commercial AFMs. This astigmatic detection system can even detect mechanical resonances due to thermal vibrations of microfabricated cantilevers. This DVD-based astigmatic measuring system is small and compact, and it has the potential to reach detection bandwidth over 100 MHz. This may lead to future development of high sensitivity and high-speed AFMs as well as high-sensitivity MEMS or NEMS-based chemical or biological sensors. The published works have also been covered by nanotechweb on March 13, 2008 as a major story. A National project aiming at further development of the astigmatic optical system is currently underway. Several proto-types of DVD-based AFMs have been developed successfully. (Appl. Phys. Lett. 91, 221908 (2007); Nanotechnology 19, 115501 (2008))
