Direct measurement of the Goos-H änchen shift using a scanning quadrant detector and a polarization maintaining fiber

High precisionmeasurements of opticalbeam shifts are important in various fields including sensing, atomic force microscopy, andmeasuringbeam shifts at interfaces. Sub-micron shifts are generallymeasured by indirect techniques such as weakmeasurements. We demonstrate a straightforward and robustmeasurement scheme for the shift, based on a scanning quadrantphotodiode (QPD) that is biased using a lownoise electronic circuit. The shift ismeasured with respect to a referencebeam that is co-propagating with the signalbeam. Thus, the shift of the signalbeam is readout directly as the difference between the x-intercepts of the QPD scan plot of the signal and referencebeams versus the position of thedetector. Tomeasure thebeam shift, we usepolarization multiplexing scheme where the p-polarized signal and s-polarized referencebeams are modulated at two different frequencies and co-launched into a polarization-maintaining fiber. Both the signal and referencebeam positions are readout by two lock-inamplifiers simultaneously. In order to demonstrate the utility of this method, we perform a directmeasurement of Goos-H änchen shift of abeam that is reflected from a planegold surface. Accuracy of 150 nm is achieved using this technique.

Source: Review of Scientific Instruments - October 17, 2016 Category: Physics Authors: Venkata Jayasurya Yallapragada, Gajendra L. Mulay, Ch. N. Rao, Ajith P. Ravishankar and Venu Gopal Achanta Source Type: research