The axial position of a laser-trapped particle has been controlled by modification of the wave front by means of a membrane deformable mirror. The mirror gives wave-front modulation in terms of Zernike polynomials. By modulation of the Zernike defocus term we can modulate the particle position under conditions of laser trapping. A polystyrene particle of 1-μm diameter was moved along the optical axis direction for a distance of 2370 nm in minimum steps of 55.4 nm. We also demonstrated particle oscillation along the optical axis by changing the focal position in a sinusoidal manner. From the frequency dependency of the amplitude of particle oscillation we determined the spring constant as 91.7nN/m .
© 2003 Optical Society of America
Taisuke Ota, Satoshi Kawata, Tadao Sugiura, Martin J. Booth, Mark A. A. Neil, Rimas Juškaitis, and Tony Wilson, "Dynamic axial-position control of a laser-trapped particle by wave-front modification," Opt. Lett. 28, 465-467 (2003)