Photonic active filters based on SiC multilayer structures

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Photonic active filters based on SiC multilayer structures M. A. Vieira1,3, M. Vieira1,2, P. Louro1,2, V. Silva1,2, J. Costa1,2, M. Barata1,2 1

Electronics Telecommunication and Computer Dept. ISEL, R. Conselheiro Emídio Navarro, 1949-014 Lisboa, Portugal Tel: +351 21 8317290, Fax: +351 21 8317114, [email protected] 2 CTS-UNINOVA, Quinta da Torre, Monte da Caparica, 2829-516, Caparica, Portugal. 3 DEE-FCT-UNL, Quinta da Torre, Monte da Caparica, 2829-516, Caparica, Portugal.

ABSTRACT Tunable WDM converters based on amorphous SiC multilayer photonic active filters are analyzed. The manipulation of the magnitude is achieved through appropriated front and back backgrounds. Transfer function characteristics are studied. Results show that the light-activated device combines the demultiplexing operation with the simultaneous photodetection and self amplification of an optical signal. Depending on the wavelength of the external background and irradiation side, it acts either as a short- or a long- pass band filter or as a band-stop filter. A combinational logic function is mapped onto an active two stage optoelectronic logic circuit. An algorithm to decode the multiplex signal is established. An optoelectronic model supports the optoelectronic logic architecture. INTRODUCTION Systems that transmit, receive, and/or process intelligence require some sort of modulation, which is the deliberate distortion of a carrier to impress intelligence (data) upon it, that subsequently allows the information recovery. Data transmission can be improved using the wavelength division multiplexing-demultiplexing technique, WDM, [1]. In digital hardware, it corresponds to a building block named multiplexer (MUX). Logic theory shows that all digital operations may be reduced to elementary logic functions [2]. A digital system can be seen as a collection of AND, OR, and NOT circuits. The purpose of this paper is to present a new optical logic architecture that offers considerable improvements in reconfigurability [3]. The expression of a logic function can be mapped onto a parallel connection of p-i-n optical filter based on a-Si:H and a-SiC:H double structures. DEVICE CONFIGURATION AND OPERATION The sensor element is a multilayered heterostructure based on Optical bias a-Si:H and a-SiC:H produced by PE-CVD at 13.56 MHz radio frequency. The configuration of the device, shown in Fig. 1, includes ITO n two stacked p-i-n structures (p(a-SiC:H)- í'(a-SiC:H)-n(a-SiC:H)-p(apin2 i-Si:H (1000 nm) P SiC:H)-i(a-Si:H)-n(a-Si:H)) sandwiched between two transparent n i’-SiC:H (200 nm) pin1 contacts. The thicknesses and optical gap of the í'- (200nm; 2.1 eV) P ITO Glass and i- (1000nm; 1.8eV) layers are optimized for light absorption in λB the blue and red ranges, respectively [4]. As a result, both front and Optical bias λ G λR back pin structures act as optical filters confining, respectively, the Fig. 1 Device operation. blue and the red optical carriers to their active absorption areas. The device operates within the visible range using as input color cha