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Vol. 10, Special Issue, February 2011, pp.96-120



Double Pin Photodiodes with Two Optical Gate Connections for Light Triggering: A Capacitive Two-phototransistor Model


1,2Manuel A. Vieira, 1,2,3Manuela Vieira, 1,2Jo„o Costa, 1,2Paula Louro,
1,2Miguel Fernandes, 1,2A. Fantoni

1Electronics Telecommunications and Computer Dept, ISEL, Lisbon, Portugal

2CTS-UNINOVA, Quinta da Torre, 2829-516, Caparica, Portugal

3DEE-FCT-UNL, Quinta da Torre, 2829-516, Caparica, Portugal

E-mail: mvieira@deetc.isel.ipl.pt, mv@isel.ipl.pt, jcosta@deetc.isel.ipl.pt, plouro@deetc.isel.ipl.pt, mfernandes@deetc.isel.ipl.pt



Received: 29 October 2010   /Accepted: 11 January 2011   /Published: 8 February 2011


Abstract: Light-activated multiplexer/demultiplexer silicon-carbon devices are analyzed. An electrical model for the device operation is presented and used to compare output signals with experimental data. An algorithm that takes into accounts the voltage and the optical bias controlled sensitivities was developed. The device is a double piín/pin a-SiC:H heterostructure with two optical gate connections for light triggering in different spectral regions. Multiple monochromatic pulsed communication channels were transmitted together, each one with a specific bit sequence. The combined optical signal was analyzed by reading out, under different applied voltages and optical bias, the generated photocurrent across the device. Experimental and simulated results show that the output multiplexed signal has a strong nonlinear dependence on the light absorption profile, i.e., on the incident light wavelength, bit rate and intensity under unbalanced light generation of carriers. By switching between positive and negative voltages or by applying an appropriated optical bias wavelength the input channels can be recovered or removed. A capacitive two connected phototransistor model gives insight into the device operation and explains the decode algorithms.


Keywords: Optical sensors, Wavelength division multiplexing-demultiplexing devices, Electrical simulation, Optical communications


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