Implementation of the spatial and the temporal cross-ambiguity function for waveguide fields and optical pulses

Time-frequency signal processing of terahertz pulses

We demonstrate that some signal-processing techniques, such as the fractional Fourier transform and the spectrogram, which are known to be effective for optical signals, can be implemented at terahertz frequencies and with available terahertz devices. These techniques, contrary to the frequency-resolved optical-gating method for pulse characterization, do not require nonlinear media, which do not exist at terahertz frequencies. Thus the fractional Fourier transform or the spectrogram offers the only possibility of characterizing terahertz pulses simultaneously in time and frequency.

One-step measurement of optical fields in multimode circular fibers

We propose to determine the optical field in multimode circular fibers by using a one-step method that measures the Wigner distribution function of a section of the field in the fiber. This method allows an estimation not only of the power carried by each mode but also of the relative phases of different modes in the fiber. An additional measurement with the same setup can even determine the propagation constants of different modes. An example is provided, and the connection of this method of field recovery to the coupling coefficient between fibers and light sources is also discussed.