Michael S. Mermelstein

Multibeam interferometric illumination as the primary source of resolution in optical microscopy

High-resolution images of a fluorescent target were obtained using a low-resolution optical detector by illuminating the target with interference patterns produced with 31 coherent beams. The beams were arranged in a cone with 78° half angle to produce illumination patterns consistent with a numerical aperture of 0.98. High-resolution images were constructed from low-resolution images taken with 930 different illumination patterns. Results for optical detectors with numerical apertures of 0.1 and 0.2 were similar, demonstrating that the resolution is primarily determined by the illuminator and not by the low-resolution detector. Furthermore, the long working distance, large depth of field, and large field of view of the low-resolution detector are preserved.

Lensless focusing with subwavelength resolution by direct synthesis of the angular spectrum

We consider the coherent superposition of unfocused wave fronts for lensless focusing of electromagnetic waves with subwavelength resolution. Near the focal point, intensity distributions generated using the approach approximate those generated using lenses. Far from the focal point, discretization of spatial frequencies results in a trade-off between the number of wave fronts and the accuracy of the approximation. We experimentally demonstrate the feasibility of the approach by generating an approximation of an azimuthally polarized Bessel beam with a focal spot diameter (full width at half maximum intensity) of 0.37λ.

Reflective acousto-optic modulation with surface acoustic waves

A reflective optical modulator based on acousto-optic modulation of light by a mirror corrugated with surface acoustic waves is presented. Modulation of optical amplitude, frequency, and phase is demonstrated at visible (633- and 488-nm) and deep UV (244-nm) wavelengths. The reflective modulator has eight channels and achieves a maximum first-order diffraction efficiency of 6.0%.