Improved axial position detection in optical tweezers measurements.

We investigate the axial position detection of a trapped microsphere in an optical trap by using a quadrant photodiode. By replacing the photodiode with a CCD camera, we obtain detailed information on the light scattered by the microsphere. The correlation of the interference pattern with the axial position displays complex behavior with regions of positive and negative interference. By analyzing the scattered light intensity as a function of the axial position of the trapped sphere, we propose a simple method to increase the sensitivity and control the linear range of axial position detection.

[1]  Michelle D. Wang,et al.  Stretching DNA with optical tweezers. , 1997, Biophysical journal.

[2]  E. Stelzer,et al.  Photonic force microscope based on optical tweezers and two-photon excitation for biological applications. , 1997, Journal of structural biology.

[3]  K. Svoboda,et al.  Biological applications of optical forces. , 1994, Annual review of biophysics and biomolecular structure.

[4]  Watt W. Webb,et al.  Measurement of small forces using an optical trap , 1994 .

[5]  R. Dickinson,et al.  Direct Measurement of Static and Dynamic Forces between a Colloidal Particle and a Flat Surface Using a Single-Beam Gradient Optical Trap and Evanescent Wave Light Scattering , 2001 .

[6]  C. Schmidt,et al.  Interference model for back-focal-plane displacement detection in optical tweezers. , 1998, Optics letters.

[7]  Sonia Grego,et al.  The Motion of a Single Molecule, the λ-Receptor, in the Bacterial Outer Membrane , 2002 .

[8]  H. Flyvbjerg,et al.  Power spectrum analysis for optical tweezers , 2004 .

[9]  E. Stelzer,et al.  Three‐dimensional high‐resolution particle tracking for optical tweezers by forward scattered light , 1999, Microscopy research and technique.

[10]  S. Block,et al.  Versatile optical traps with feedback control. , 1998, Methods in enzymology.

[11]  E. Stelzer,et al.  Three-dimensional position detection of optically trapped dielectric particles , 2002 .

[12]  Steven M Block,et al.  Resource Letter: LBOT-1: Laser-based optical tweezers. , 2003, American journal of physics.