Extended depth-of-focus (EDOF) diffractive lenses produce a narrow and long focusing region which have many applications on microscopy, laser focusing or contact and intraocular lenses. Several designs have been proposed to achieve EDOF by angularly modulating the focal length. Nevertheless, when the focus is highly elongated, some undesired intensity fluctuations are produced. To solve this problem, we have generalized this type of lenses by defining their focal length as a Fourier series. Moreover, we have used Particle Swarm Optimization algorithm to optimize its Fourier series coefficients and generate an enhanced design. The performance of our Fourier Series Diffractive Lens (FSDL) is parameterized through the Full Width at Half Maximum (FWHM) of the beam and the uniformity of the intensity along the optical axis. Our results prove that the FSDL beam on the focal region is narrower and much more uniform than previous EDOF designs, showing the enhancement of the proposed EDOF lens.
Spatial light modulator is an essential electro-optical device in applications that require to modulate the amplitude, phase, or polarization of light. Its proper use requires to determine its Mueller matrix. In this work, we compare different methods to calculate the condition number of Mueller-Stokes polarimetry techniques, which defines their maximum relative error. Combining experimental and calculated values, we determined the most suitable method for calculating the condition number.
We designed, fabricated and tested a Vector Diffractive Optical Element (VDOE) to simultaneously determine the Stokes vector of light. It comprises several sectors. Each one is a vector Fresnel zone plate which focuses the light on separate foci and has different polarization properties. The polarization state is calculated from their intensities.
From simulations, we could identify the error sources that were analytically removed. The residual uncertainty after applying our corrections was as low as 6x10^(-5). The uncertainty obtained for our fabricated VDOE, 3.33 %, is competitive with the results from state-of-the-art techniques.
Refractometric sensors based on plasmonic resonances can be modified to operate using an interrogation method based on the optoelectronic response of the device. In this contribution we show how the bolometric effect can be used to generate a signal depending on the change of the refractive index of the analyte. The design has been tuned to sense variations in the range of aqueous media. We have also proposed a modification of a perovskite solar cell to sense variations in the index of refraction of air. These changes in the interrogation method have required a modification of the definitions of the sensitivity and Figure of Merit of such types of sensors. The results show a performance that is competitive with other refractometric sensors and allows an operation method that relies on the measurement of electric, or electronic, parameters.
Ultrathin amorphous silicon hydrogenated (aSi-H) solar cells grown on a one-dimensional (1-D) dielectric subwavelength gratings improve the short circuit current by a factor of more than 51% when compared with conventional, flat ultrathin aSi-H devices. This improvement is possible due to several mechanisms. In addition the increase in exposed area caused by the nanostructured surface, a reliable computational electromagnetic evaluation of the interaction of the solar spectrum with the cell structure demonstrates that absorption at the active layer is enhanced and also reflectivity is decreased. In addition, the absorbed power at the nonactive layers is larger, helping to increase the temperature and mitigate the Staebler–Wronski effect. The detailed analysis of the power flux inside the structure has also shown that funneling and guiding mechanism are at play, increasing the optical path within the active layer that produces a better performance of the cell.
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