An optoelectromechanical light sensor at 1.55 μm

We have the device under test, which is either our detector or a piece of metal for calibration, mounted under the vibrating AFM tip. To activate the sample we either apply a changing voltage to the tip which generates an electrostatic force, or apply laser light to the sample which deforms the surface potential, altering the electrostatic force. With our AFM we feed the phase output of the vibrating tip to an oscilloscope and lockin amplifier. The lockin amplifier is synchronized with the function generator. This allows us to sense the phase change of the tip at the frequency of applied voltage or light. We monitor the phase change as opposed to the amplitude because it is much more sensitive to forces on the tip.