Dynamic axial position control of a laser trapped particle by wave front modification

Opt. Lett., Vol. 28, Pt. 6, March 2003, 465-467. T. Ota, S. Kawata. et al.

The axial position of a laser-trapped particle has been controlled by modification of the wave front by meansof 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 lasertrapping. A polystyrene particle of 1-mm diameter was moved along the optical axis direction for a distanceof 2370 nm in minimum steps of 55.4 nm. We also demonstrated particle oscillation along the optical axisby changing the focal position in a sinusoidal manner. From the frequency dependency of the amplitude ofparticle oscillation we determined the spring constant as 91.7 nNm.

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