RESUMEN
Compressive sampling has been previously proposed as a technique for sampling radar returns and determining sparse range profiles with a reduced number of measurements compared to conventional techniques. By employing modulation on both transmission and reception, compressive sensing in ranging is extended to the direct measurement of range profiles without intermediate measurement of the return waveform. This compressive ranging approach enables the use of pseudorandom binary transmit waveforms and return modulation, along with low-bandwidth optical detectors to yield high-resolution ranging information. A proof-of-concept experiment is presented. With currently available compact, off-the-shelf electronics and photonics, such as high data rate binary pattern generators and high-bandwidth digital optical modulators, compressive laser ranging can readily achieve subcentimeter resolution in a compact, lightweight package.
RESUMEN
Using a four-mode theoretical analysis we show that highly efficient anti-Stokes conversion in waveguides is more challenging to realize in practice than previously thought. By including the dynamics of conversion to 2(nd) Stokes via stimulated Raman scattering and four-wave mixing, models predict only narrow, unstable regions of highly efficient anti-Stokes conversion. Experimental results of single-pass Raman conversion in confined capillary waveguides validate these predictions. This places more stringent conditions on systems that require highly efficient single-pass anti-Stokes conversion.
RESUMEN
A data-processing technique is proposed for use with conventional frequency-chirped absorption spectroscopy to ensure accurate mapping of spectral features into time-domain signatures with arbitrarily fast readout chirp rates. This technique recovers the spectrum from a signal that is distorted owing to the fast chirp rate and therefore facilitates fast measurement of the spectral features over a broad spectral range with high resolution. Both numerical simulations and experimental results are presented.