No abstract

This paper presents a fast and efficient method for sizing power/ground networks. No restrictions on network topology or number of supplying pads are imposed. Wire widths are calculated such that the weighted area of wire segments is minimized while electromigration and voltage drops constraints are fulfilled. The algorithm proposed here runs 50% faster than the best methods reported for tree type network topologies.

No abstract

Imaging the retina of cataractous patients is useful to detect pathologies before the cataract surgery is performed. However, for conventional ophthalmoscopes, opacifications convert the lens into a scattering medium that may greatly deteriorate the retinal image. In this paper we show, as a proof of concept, that it is possible to surpass the limitations imposed by scattering applying to both, a model and a healthy eye, a newly developed ophthalmoscope based on single-pixel imaging. To this end, an instrument was built that incorporates two imaging modalities: conventional flood illumination and single-pixel based. Images of the retina were acquired firstly in an artificial eye and later in healthy living eyes with different elements which replicate the scattering produced by cataractous lenses. Comparison between both types of imaging modalities shows that, under high levels of scattering, the single-pixel ophthalmoscope outperforms standard imaging methods.

We examine the temporal coherence properties of trains of nonidentical short optical pulses in the framework of the second-order coherence theory of nonstationary light. Considering Michelson's interferometric measurement of temporal coherence, we demonstrate that time-resolved interferograms reveal the full two-time temporal coherence function of the partially coherent pulse train. We also show that the result given by the time-integrated Michelson interferogram equals the true degree of temporal coherence only when the pulse train is quasi-stationary, i.e., the coherence time is a small fraction of the pulse duration. True two-time and integrated coherence functions produced by specific models representing perturbed trains of mode-locked pulses and supercontinuum pulse trains produced in nonlinear fibers are illustrated.

In this paper, a multifunctional metasurface capable of switching between an absorber and a polarization converter is presented. The active metasurface comprises diamond‐shaped unit cells embedded with PIN diodes. The characteristic of the design lies in its capability of exhibiting multifunctionality at the same frequency of operation. The structure behaves as an absorber and linear polarization converter around 15 and 17 GHz when the PIN diode is switched ON and OFF, respectively. The working principle is demonstrated with the help of simulated results. Finally, the design is fabricated and measured, and it is seen that the results are in accordance with that of the simulated ones, establishing the concept behind switchability of absorber and polarization converter.

A new class of partially coherent model sources is introduced on the basis of the second-order coherence theory of nonstationary optical fields. These model sources are spatially fully coherent at each frequency but can have broadband spectra and variable spectral coherence properties, which lead to reduced spatiotemporal coherence in the time domain. The source model is motivated by the spectral coherence properties of supercontinuum pulse trains generated in single-spatial-mode optical fibers. We demonstrate that such broadband light is highly (but not completely) spatially coherent, even though the spectral and temporal coherence properties may vary over a wide range. The model sources introduced here are convenient in assessing the spatiotemporal coherence of broadband pulses in optical systems.

We show that space-time resolved measurements of interference patterns produced by an equal-path Michelson's interferometer with tilted mirrors allow one to construct the two-time mutual coherence function (MCF) associated with temporally partially coherent pulse trains. If the pulses are quasi-stationary in the sense that the coherence time is less than ∼25% of the pulse width, conventional time-integrated measurements with Michelson's interferometer provide the correct MCF. Such time-integrated measurements, combined with suitable calibration processes, are sufficient for the determination of the MCF also if the complex degree of temporal coherence is independent of the absolute time, provided that the mean temporal intensity distribution of the pulses is known.