Scanning force microscope using an optical trap

摘要

A scanning force microscope utilizes a probe consisting of a glass stylus, or probe, positioned and oriented by an optical trap. The probe is an optically transparent cylinder having at least one tip on its axis with an apex dimension less than one wavelength of the light used for the trap. An optical displacement sensor utilizing forward scatter or an optical interferometer detects the motion of the probe caused by the force between the tip and an object to be scanned. Mutual scanning displacement between the probe and the object is carried out by moving a support stage along x/y coordinates or by movement of the light beam forming the optical trap along these coordinates. Radiation forces due to the three-dimensional intensity distribution of the light in the optical trap allow the probe to be positioned with precise control and with a low spring constant, allowing resolution in the range of lambda /100, with the probe being capable of measuring forces smaller than 0.1 pN.