Increased sensitivity in a-SiC pinpin multilayers in the VIS-NIR range under UV light
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Increased sensitivity in a-SiC pinpin multilayers in the VIS-NIR range under UV light V. Silva1,2, I. Rodrigues1 , M. A Vieira1,2, P. Louro1,2, M. Vieira1,2,3 1
Electronics Telecommunication and Computer Dept. ISEL, R. Conselheiro Emídio Navarro, 1959-007 Lisboa, Portugal 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 In this paper we experimentally demonstrate the use of near-ultraviolet steady state illumination to increase the spectral sensitivity of a double a-SiC/Si pi’n/pin photodiode beyond the visible spectrum (400 nm-880 nm). The concept is extended to implement a one by four wavelength division multiplexer with channel separation in the visible/near infrared range. Optoelectronic characterization of the device is presented and shows the feasibility of tailoring the wavelength and bandwidth of a polychromatic mixture. Several monochromatic pulsed lights in the VIS/NIR range, separately or in a polychromatic mixture illuminated the device. Independent tuning of the wavelengths is performed by steady state 390 nm optical bias superimposed from front and back sides. Results show that, front background enhances the lightto-dark sensitivity of the medium, long and infrared wavelength channels, and quench strongly the shorter wavelengths. Back background has the opposite effect; it only enhances the channel magnitude in short wavelength range and strongly reduces it in the long ones. This nonlinearity provides the possibility for selective tuning a specific wavelength. A capacitive optoelectronic model supports the experimental results. A numerical simulation is presented. INTRODUCTION Optical Wireless Communication, in the infrared and visible range, is an attractive solution, especially in environment settings where radio communication encounters difficulties. Visible Light Communication (VLC) has several advantages: Light communication is visible, so it is easy to determine who can listen or receive a message. A side effect is that light communication does not require part of the radio spectrum and can therefore be seen as a suitable extension in bandwidth-limited scenarios. Visible light is present in many places, so there is the opportunity to combine light communication with lighting design to let VLC coexist with, or even benefit from, the lighting setup present in many offices, homes, or institutions. The VLC principle is a relatively new approach for optical free space applications. However, it has been so far considered mainly for internet access or home networks, but more applications are feasible [1, 2, 3]. SiC active filter based on a-Si technology, has recently proven its merits to operate with visible optical signals. To enhance the transmission capacity and the application flexibility of the optical communication efforts have to be considered, namely the fundamentals of Wavelength Division Multiplexing based on a-SiC:H light controlled filters when different visible signals
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