New paper in Optics Letters, Vol. 40, Issue 8, pp. 1881-1884 (2015):

Tomographic phase microscopy with 180° rotation of live cells in suspension by holographic optical tweezers

Mor Habaza, Barak Gilboa, Yael Roichman, and Natan T. Shaked

Abstract: We present a new tomographic phase microscopy (TPM) approach that allows capturing the three-dimensional refractive-index structure of single cells in suspension without labeling using 180° rotation of the cells. This is obtained by integrating an external off-axis interferometer for wide-field wave front acquisition with holographic optical tweezers (HOTs) for trapping and micro-rotation of the suspended cells. In contrast to existing TPM approaches for cell imaging, our approach does not require anchoring the sample to a rotating stage nor is it limited in angular range as is the illumination rotation approach, and thus it allows TPM of suspended live cells in a wide angular range. The proposed technique is experimentally demonstrated by capturing the three-dimensional refractive-index map of yeast cells while collecting interferometric projections at an angular range of 180° with 5° steps. The interferometric projections are processed by both the filtered back-projection method and the diffraction-theory method. The experimental system is integrated with spinning-disk confocal fluorescent microscope for validation of the label-free TPM results.

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3-D refractive index map of yeast cells obtained by the proposed TPM-HOTs technique.