Stiffer optical tweezers through real-time feedback control

• DOI: 10.1063/1.2940339
• Publication Date: 2008-06-07T23:52:31Z
• Authors: Anders E. Wallin; Heikki Ojala; Edward Hæggström; Roman Tuma
• Keywords: Position (finance); Trap (plumbing); Tweezers; SIGNAL (programming language); Optical power; Position sensor

Using real-time re-programmable signal processing we connect acousto-optic steering and back-focal-plane interferometric position detection in optical tweezers to create a fast feedback controlled instrument. When trapping 3μm latex beads water find that proportional-gain position-clamping increases the effective lateral trap stiffness ∼13-fold. A theoretical power spectrum for bead fluctuations during position-clamped is derived agrees with experimental data. The loop delay, ∼19μs our experiment, limits maximum achievable stiffness.