John F. Whitaker

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A microwave electric-field mapping system based on electrooptic sampling has been developed using micromachined GaAs crystals mounted on gradient index lenses and single-mode optical fibers. The probes are able to detect three orthogonal polarizations of electric fields and, due to the flexibility and size of the optical fiber, can be positioned not only(More)
A review of the application of semiconductor layers grown at low substrate temperatures to ultrafast optoelectronics is presented. The films, grown by molecular beam epitaxy primarily around 200 °C and subsequently annealed, are demonstrated to have high resistivity, high mobility, an ultrashort carrier lifetime, and a high dielectric breakdown. This(More)
We demonstrate the reconstruction of one- and two-dimensional objects by numerically backpropagating measured scattered terahertz transients. The spatial resolution determined by the Sparrow criterion is found to correspond to approximately 30% of the peak wavelength and 85% of the mean wavelength of the power spectrum of the single-cycle waveform.
In 1890 Gouy showed that a focused electromagnetic beam will acquire an additional axial 180± phase shift with respect to a plane wave as it evolves through its focus [1–3]. This phase shift has important consequences throughout the electromagnetic spectrum. It explains the phase advance postulated by Fresnel for the secondary Huygens’ wavelets emanating(More)
G. A. Garrett,1,2 T. F. Albrecht,1,2 J. F. Whitaker,1 and R. Merlin1,2,3 1Center for Ultrafast Optical Science, The University of Michigan, Ann Arbor, Michigan 48109-2099 2The Harrison M. Randall Laboratory of Physics, The University of Michigan, Ann Arbor, Michigan 48109-1120 3Department of Physics, Hong Kong University of Science and Technology, Clear(More)
A comprehensive electrooptic field-mapping technique is applied to the characterization of near-field radiation patterns above a microstrip patch antenna. The amplitude and phase maps of three orthogonal electric-field components, measured using electrooptic crystals above the patch, also have revealed the transition from the near field to the far field of(More)