In situ wavefront correction and its application to micromanipulation

In any optical system, distortions to a propagating wavefront reduce the spatial coherence of a light field, making it increasingly difficult to obtain the theoretical diffraction-limited spot size. Such aberrations are severely detrimental to optimal performance in imaging, nanosurgery, nanofabrication and micromanipulation, as well as other techniques within modern microscopy. We present a generic method based on complex modulation for true in situ wavefront correction that allows compensation of all aberrations along the entire optical train. The power of the method is demonstrated for the field of micromanipulation, which is very sensitive to wavefront distortions. We present direct trapping with optimally focused laser light carrying power of a fraction of a milliwatt as well as the first trapping through highly turbid and diffusive media. This opens up new perspectives for optical micromanipulation in colloidal and biological physics and may be useful for various forms of advanced imaging. Distortions in a propagating optical wavefront — known as aberrations — prevent the achievement of a diffraction-limited beam spot. A generic in situ wavefront correction method based on complex modulation is demonstrated, allowing compensation for all aberrations along the whole optical train. The scheme is used for direct trapping through highly turbid and diffusive media, opening up new applications for optical micromanipulation in colloidal and biological physics.