Optical Sciences

Biomolecules and nanostructures

The Optical Sciences group studies the interaction of light and matter. Our current focus is on detection and sensing/imaging with an emphasis on the development of integrated photonics. We are part of Twente University's Department of Science and Technology and member of the MESA+ institute.


Dynamic behavior of tuning fork shear-force feedback

(full pdf)

Ruiter AGT, Veerman JA, vanderWerf KO, vanHulst NF
vol 71 issue 1: p28-p30 JUL 7 1997

The dynamics of a tuning fork shear-force feedback system, used in a near-field scanning optical microscope, have been investigated, Experiments, measuring amplitude and phase of the tuning fork oscillation as a function of driving frequency and tip-sample distance, reveal that the resonance frequency of the tuning fork changes upon approaching the sample. Either amplitude or phase of the tuning fork can be used as distance control parameter in the feedback system. Using amplitude a second-order behavior is observed while with phase o­nly a first-order behavior is observed, and confirmed by numerical calculations. This first-order behavior results in an improved stability of our feedback system, A sample consisting of DNA strands o­n mica was imaged which showed a height of the DNA of 1.4 nm. (C) 1997 American Institute of Physics.
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