VIS/NIR wavelength selector based on a multilayer pi'n/pin a‐SiC:H optical filter

Abstract

In this paper, we present a tandem visible/nearinfrared (VIS/NIR) wavelength selector based on a multilayer a‐SiC:H optical filter that requires appropriate near‐ultraviolet steady states optical switches to select the desired wavelengths in the VIS/NIR ranges. Spectral response measurements are presented and show the feasibility of tailoring the wavelength and bandwidth of a polychromatic mixture of different wavelengths. The selector filter is realized by using a two terminal double pi'n/pin a‐SiC:H photodetector. Five visible/infrared communication channels are transmitted together, each one with a specific bit sequence. The combined optical signal is analysed by reading out the photocurrent, under near‐UV steady state background. Results show that the background side and intensity works as a selector in the infrared/visible regions, shifting the sensor sensitivity. This nonlinearity allows the identification and decoding of the different input channels in the visible/infrared ranges. This concept is extended to implement a 1 by 5 wavelength division multiplexer with channel separation in the VIS/NIR range and a transmission capability of 30 Kbps. The relationship between the optical inputs and the output signal is established and an algorithm to decode the Multiplexed (MUX) signal presented. An optoeletronic model gives insight on the system physics. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Switching characteristic and capacitance analysis of a-Si:H pinpin photodiodes for visible range telecommunications

“…This is required in short range optical communication applications, where for costs reasons the link is provided by Plastic Optical Fibers. This device structure has been shown very versatile and has been referenced in different photonic applications: as an integrated wavelength optical filter and photodetector for Visible Light Communication (VLC) [1], as a visible/near-infrared (VIS/NIR) wavelength selector that requires appropriate nearultraviolet steady states optical switches to select the desired wavelengths [2] and as a five channel WDM communication Multiplexer/Demultiplexer [3]. The application of this device in WDM POF-based communications presents interesting aspects for its simplicity and flexibility of application [4,5].There is indeed evidence that the retrieval of the multiplexed information is based on capacitive effects that are characteristic of this device family, being the intensity of these capacitive effects depending on light intensity and wavelength and on the background illumination conditions and applied electrical bias [6].The behaviour of the device has been explained by a photo-capacitance effect controlled through the accumulation of trapped charge localized in the intrinsic layers [7].…”