Full-field swept-source phase microscopy

We present a full-field phase microscopy technique, motivated by swept-source Fourier-domain optical coherence tomography, for quantitative nanoscale two-dimensional profiling of sample surfaces and internal structures. The optical configuration consisted of a common path interferometer, illuminating the sample with a collimated beam and detecting the back-scattered light on a 2D CCD camera. A tunable fiber Fabry Perot filter was used to sweep a narrow band (0.07nm) through the 47nm FWHM bandwidth of a superluminescent diode source. The full field of view was recorded for each discrete wavelength step, generating a spectrally indexed interferometric data cube mapping each pixel to a point on the sample. A three dimensional volume was generated by performing the discrete Fourier transform along the spectral axis. Sub-coherence length variation across a depth slice was obtained by examining the phase of the Fourier transformed data set at the selected depth. The phase stability of the system was measured to be 1.3nm for high SNR surface features. The nanoscale imaging potential of this system was demonstrated by measuring the height of patterned chrome on a USAF resolution target, the location of receptor sites on a DNA assay biochip, and the surface topography of erythrocytes in a blood smear.