3D mapping of intensity field about the focus of a micrometer-scale parabolic mirror

We report on the fabrication and diffraction-limited characterization of parabolic focusing micromirrors. Sub-micron beam waists are measured for mirrors with 10-μm radius aperture and measured fixed focal lengths in the range from 24 μm to 36 μm. Optical characterization of the 3D intensity in the near-field produced when the device is illuminated with collimated light is performed using a modified confocal microscope. Results are compared directly with angular spectrum simulations, yielding strong agreement between experiment and theory, and identifying the competition between diffraction and focusing in the regime probed.