Please use this identifier to cite or link to this item:
http://hdl.handle.net/2445/52852
Title: | Optimized back-focal-plane interferometry directly measures forces of optically trapped particles |
Author: | Farré Flaquer, Arnau Marsà, Ferran Montes Usategui, Mario |
Keywords: | Interferometria Piezoelectricitat Làsers Instruments òptics Interferometry Piezoelectricity Lasers Optical instruments |
Issue Date: | 21-May-2012 |
Publisher: | Optical Society of America |
Abstract: | Back-focal-plane interferometry is used to measure displacements of optically trapped samples with very high spatial and temporal resolution. However, the technique is closely related to a method that measures the rate of change in light momentum. It has long been known that displacements of the interference pattern at the back focal plane may be used to track the optical force directly, provided that a considerable fraction of the light is effectively monitored. Nonetheless, the practical application of this idea has been limited to counter-propagating, low-aperture beams where the accurate momentum measurements are possible. Here, we experimentally show that the connection can be extended to single-beam optical traps. In particular, we show that, in a gradient trap, the calibration product κ·β (where κ is the trap stiffness and 1/β is the position sensitivity) corresponds to the factor that converts detector signals into momentum changes; this factor is uniquely determined by three construction features of the detection instrument and does not depend, therefore, on the specific conditions of the experiment. Then, we find that force measurements obtained from back-focal-plane displacements are in practice not restricted to a linear relationship with position and hence they can be extended outside that regime. Finally, and more importantly, we show that these properties are still recognizable even when the system is not fully optimized for light collection. These results should enable a more general use of back-focal-plane interferometry whenever the ultimate goal is the measurement of the forces exerted by an optical trap. |
Note: | Reproducció del document publicat a: http://dx.doi.org/10.1364/OE.20.012270 |
It is part of: | Optics Express, 2012, vol. 20, num. 11, p. 12270-12291 |
URI: | http://hdl.handle.net/2445/52852 |
Related resource: | http://dx.doi.org/10.1364/OE.20.012270 |
ISSN: | 1094-4087 |
Appears in Collections: | Articles publicats en revistes (Física Aplicada) |
Files in This Item:
File | Description | Size | Format | |
---|---|---|---|---|
614580.pdf | 4.18 MB | Adobe PDF | View/Open |
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.