Mechanisms for photon sorting based on slit-groove arrays

Mechanisms for one-dimensional photon sorting are theoretically studied in the framework of a couple mode method. The considered system is a nanopatterned structure composed of two different pixels drilled on the surface of a thin gold layer. Each pixel consists of a slit-groove array designed to squeeze a large fraction of the incident light into the central slit. The Double-Pixel is optimized to resolve two different frequencies in the near infrared. This system shows a high transmission efficiency and a small crosstalk. Its response is found to strongly depend on the effective area shared by overlapping pixels. Three different regimes for the process of photon sorting are identified and the main physical trends underneath in such regimes are unveiled. Optimal efficiencies for the photon sorting are obtained for a moderate number of grooves that overlap with grooves of the neighbor pixel. Results could be applied to optical and infrared detectors.Comment: 12 pages, 4 figure

Transmittance of a subwavelength aperture flanked by a finite groove array \\ placed near the focus of a conventional lens

One-dimensional light harvesting structures illuminated by a conventional lens are studied in this paper. Our theoretical study shows that high transmission efficiencies are obtained when the structure is placed near the focal plane of the lens. The considered structure is a finite slit-groove array (SGA) with a given number of grooves that are symmetrically distributed with respect to a central slit. The SGA is nano-patterned on an opaque metallic film. It is found that a total transmittance of 80% is achieved even for a single slit when (i) Fabry-Perot like modes are excited inside the slit and (ii) the effective cross section of the aperture becomes of the order of the full width at half maximum of the incident beam. A further enhancement of 8% is produced by the groove array. The optimal geometry for the groove array consists of a moderate number of grooves ($\geq 4$) at either side of the slit, separated by a distance of half the incident wavelength $\lambda$. Grooves should be deeper (with depth $\geq \lambda/4$) than those typically reported for plane wave illumination in order to increase their individual scattering cross section.Comment: 7 pages, 6 figure

Mechanisms for photon sorting based on slit-groove arrays

Mechanisms for one-dimensional photon sorting are theoretically studied in the framework of a coupled-mode method. The considered system is a nanopatterned structure composed of two different pixels drilled on the surface of a thin gold layer. Each pixel consists of a slit-groove array designed to squeeze a large fraction of the incident light into the central slit. The Double-Pixel is optimized to resolve two different frequencies in the near infrared. This system shows high transmission efficiencies and a small crosstalk. It is found that the response of the system strongly depends on the effective area shared by overlapping pixels. According to such degree of overlap, photon sorting can be achieved within three different regimes, which are discussed in detail. Optimal photon-sorting efficiencies are obtained for a moderate number of grooves that overlap with grooves of the neighbor pixel. These results could be applied to both optical and infrared detectors.The authors gratefully acknowledge financial support by European Projects EC FP7-ICT PLAISIR Project Ref. 247991, the Spanish Ministry of Science and Innovation project MAT2011-28581-C02-02, and the CUD project Ref. 2013-13.Peer Reviewe

Optimal light harvesting structures at optical and infrared frequencies

One-dimensional light harvesting structures with a realistic geometry nano-patterned on an opaque metallic film are optimized to render high transmission efficiencies at optical and infrared frequencies. Simple design rules are developed for the particular case of a slit-groove array with a given number of grooves that are symmetrically distributed with respect to a central slit. These rules take advantage of the hybridization of Fabry-Perot modes in the slit and surface modes of the corrugated metal surface. Same design rules apply for optical and infrared frequencies. The parameter space of the groove array is also examined with a conjugate gradient optimization algorithm that used as a seed the geometries optimized following physical intuition. Both uniform and nonuniform groove arrays are considered. The largest transmission enhancement, with respect to a uniform array, is obtained for a chirped groove profile. Such enhancement is a function of the wavelength. It decreases from 39% in the optical part of the spectrum to 15% at the long wavelength infrared.Comment: 13 pages, 5 figure

Corrugated metallic films for detecting and sensing light in the visible and infrared regimes

En esta tesis se estudia la respuesta óptica de nanoestructuras metálicas, específicamente la transmisión a través de ranuras y agujeros estrechos con dimensiones menores que la longitud de onda de la luz incidente. Los resultados se obtienen para las regiones visible e infrarroja del espectro. En primer lugar, se optimiza la transmisión a través de una ranura central rodeada por una red simétrica de surcos periódicos, tallados en la superficie de una lámina metálica de oro. Para este sistema se describe un algoritmo que de manera sistemática permite obtener estructuras óptimas en transmisión. Se considera también el caso de estructuras no periódicas y con surcos no necesariamente idénticos. Luego se estudia la transmisión a través de una ranura, cuando la lámina metálica es iluminada por luz focalizada a través de una lente cilíndrica convencional. Se muestra que la lente hace que las eficiencias en transmisión a través de la ranura sean alrededor del 80%, la cual puede incrementarse alrededor de un 6% si se incluye la corrugación, para los casos considerados. A continuación se construye un sistema formado por dos estructuras diferentes, de ranura más corrugación, traslapados. Este sistema puede detectar dos longitudes de onda diferentes y cercanas en el espectro, ajustando la geometría de las estructuras que lo componen. En este caso se estudia la transmisión en función de la distancia relativa entre las dos ranuras. En la parte final se analiza la sensibilidad en su respuesta óptica que muestran los agujeros circulares y rectangulares aislados, frente a la polarización de la luz incidente. En caso de agujeros circulares se estudia la orientación que presenta la distribución de los campos dispersados lejanos con respecto al campo magnético incidente. De manera similar, se muestra como un agujero rectangular puede actuar como un polarizador del campo magnético incidente.Peer Reviewe