Nanometer Scale Measurement of Physical Parameters

Optical fibers have already demonstrated their performance as the sensing element to measure a large number of physical parameters such as pressure, strain, temperature, gas concentration and deformations. In recent years, the majority of research has concentrated on improving existing sensing techniques (e.g., fiber Bragg grating sensors, interferometric sensors or intensity based sensors) which have now achieved high levels of accuracy, sensitivity and stability. However, the main challenge, according to our opinion, still existing; haw to achieve the nanometer scale resolution of different physical parameters in relatively broad dynamic range. The general purpose of the proposal is a theoretical and experimental investiga-tion of fiber-optic low- and high- coherence interferometry (FO LCI, HCI) as a platform for sensor applications. The main goal is to develop a method for absolute position and displacement measurement with an accuracy better than 1 nm in a dynamic range of several tens of micrometers, i.e. to reach a resolution-to-range-ratio of 1 ppm or better. From the short survey given in the proposal we pointed out there was no one single method enable to fulfill such demand. Our novel approach 1) combine two interferometric principles (low- and high-coherence) inside one system, by introducing an element we termed as double receiving interferometer (DRI), and 2) avoid the use of any kind of moving parts by employing CCD electronic scanning. The scanning and signal processing should be done in two consecutive steps, the first one for rough deter-mination of central fringe position, as in ordinary LCI system, and the second one for precise phase measurement by spatial phase-shifting technique, as in ordinary HCI system. The main advantages of this novel technique are relatively low resolution dema-nds in every single evaluation step. It is sufficient to reach only a thousand resoluble and accurate values in a single step, allowing a lower system signal-to-noise ratio (SNR). The main challenges we are expecting are: design and manufacturing of a compact DRI, evaluation of the most suitable algorithm for signal processing and suppression of back-reflected radiation toward the high coherence source as well as reduction of interferometric intensity noise into an interferometric scheme. The main risks are thermal, acoustical and vibrational system instabilities and behavior of two-interferometer-in- tandem configuration. The proposed measuring technique performed by "all-fiber" design can have a strong impact onto development of nowadays emerging fields: nanotechnology, life science and biomedicine.