Normally, femtosecond light pulses that cross at a nonzero angle overlap over only a small region in space. This limitation can be overcome by the use of diffraction orders of a grating. We consider an arrangement in which, on diffraction of a femtosecond pulse by a grating, two beams that correspond to the first-order diffraction maxima are recombined at the image plane by a system of two confocal lenses. In this arrangement the beams overlap over the their full aperture, with the short duration of the pulses being preserved. We demonstrate the use of this setup as a simple autocorrelator and discuss a possible application to time-resolved vibrational spectroscopy.
Phonon-polariton dispersion is characterized in ferroelectric lithium tantalate and lithium niobate through femtosecond time-resolved impulsive stimulated Raman scattering (ISRS). An improvement in the ISRS setup permits optical heterodyne detection of the signals. In addition to substantially increasing the sensitivity and accuracy of the measurements, the phase sensitivity of heterodyne detection makes it possible to fully characterize the polariton wave after it has propagated outside of the excitation region. The detection of propagating responses with heterodyned ISRS is explored theoretically and experimentally. Discrepancies in earlier results reported for these materials are resolved.
Rapid, inline inspection of wafers and reticles for minimum pitch defects is expected to be a significant technical challenge at the 11nm node. With the possible future adoption of EUV lithography, increasingly exotic materials and complex device architectures, projecting end user requirements is a difficult feat 4 to 5 years out. The present work progresses through projections of these requirements and surveys the various options available to the industry, supported by microscopy simulations. The main conclusion is that the industry needs to support pathfinding projects to develop super-resolution techniques, wavelength scaling and highly multiplexed, high defect contrast ebeam inspection.
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