Near-UV background as a bridge between visible and infrared communication
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Near-UV background as a bridge between visible and infrared communication M. Vieira1,2,3, M. A. Vieira1,2, V. Silva 1,2, I. Rodrigues1, P. Louro1,2 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 present a monolithically integrated wavelength selector based on a multilayer pi’n/pin a-SiC:H integrated optical filter that requires appropriate near-ultraviolet steady states optical switches to select the desired wavelengths in the VIS-NIR ranges. Results show that the background intensity works as a selector in the infrared/visible regions, shifting the sensor sensitivity. Low intensities select the NIR range while high intensities select the visible part accordingly to its wavelength. Here, the optical gain is very high in the red range, decreases in the green range, and stays near one in the blue region decreasing strongly in the near-UV range. The transfer characteristics effects due to changes in steady state light intensity and wavelength backgrounds are presented. The relationship between the optical inputs and the output signal is established when a multiplexed signal is analyzed. INTRODUCTION Newly developed technologies for infrared telecommunication systems allowed the increase of capacity, distance and functionality, switching and control with the design of new reconfigurable logic active filter gates by “bridging the gaps” and combining the optical filters properties [1]. Expanding far beyond traditional applications in optical interconnects at telecommunication wavelengths [2, 3], the SiC nanophotonic integrated circuit platform has recently proven its merits for working with visible range optical signals. To enhance the transmission capacity and the application flexibility of optical communication efforts have to be considered, namely the Wavelength Division Multiplexing based on tandem a-SiC:H light controlled filters, when different visible signals are encoded in the same optical transmission path [4, 5]. In this paper, the shift of the visible range to telecom band can be accomplished using the same wavelength selector but under appropriated near ultraviolet optical bias, acting as reconfigurable active filters in the visible and near infrared ranges. These active filters act as interface devices that establish the bridge between the infrared and red spectral range playing a key role to bridging the infrared and the visible optical communication technology. They can be used to realize different filtering processes such as: amplification, switching, and wavelength conversion. DEVICE DESIGN, CHARACTERIZATION AND OPERATION The light tunable filter is realized by using a double pi’n/pin a-SiC:H photodetector with TCO front and back biased optical gating elements as depicted in Figure 1. The active device consists of a p-i'(a-SiC:H)-n/p-i(a-Si:H)-n heterost
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