We propose a new hollow-core fiber that employs a rib-waveguide geometry for improved gas or liquid sensing. This
waveguide supports a true guided mode that is connected laterally to the external environment through a hollow slab.
Such designs eliminate the requirement of small transverse holes and open up new opportunities for sensing.
We discuss two techniques for measuring space-time coupling in ultrashort pulses using spectral phase interferometry for direct electric-field reconstruction (SPIDER). The first technique, Spatially Encoded Arrangement for SPIDER (SEA SPIDER), requires reduced spectral resolution as compared to conventional SPIDER techniques and is therefore ideally suited for very large bandwidth pulses. In addition, this method results in a spatially resolved reconstruction of the temporal field and allows for the characterization of some types of space-time coupling. The second technique, Space Time SPIDER (ST SPIDER), couples spatial shearing and spectral shearing interferometry to fully characterize any arbitrary space-time field without assumptions about the ultrashort pulse or the type of coupling present. Experimental demonstrations of both techniques are presented.