Novel device for implementation of WDM in the visible spectrum
- PDF / 10,195,918 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 41 Downloads / 198 Views
Novel device for implementation of WDM in the visible spectrum P. Louro1,2, M. Vieira1,2,3, M. A. Vieira1,2, V. Silva1,2, A. Fantoni1,2 Electronics Telecommunications and Computer Dept, ISEL, Lisbon, Portugal. 2 CTS-UNINOVA, Lisbon, Portugal. 3 DEE-FCT-UNL, Quinta da Torre, Monte da Caparica, 2829-516, Caparica, Portugal 1
ABSTRACT In this paper we report the use of a device based on two multilayered a-SiC:H/a-Si:H stacked heterostructures to photodetect and demultiplex optical signals of the visible spectrum. Both heterostructures were optimized for the detection of short and long wavelengths within the visible range. The optoelectronic characterization of the device includes spectral response measurements under reverse bias and using different optical steady state light conditions to soak the device. Results show that the device photocurrent signal measured using appropriate steady state optical bias, allows the separate detection of the input transmitted signals which enables the demultiplexing task. A numerical simulation, gives insight into the transduction mechanism to explain the device wavelength selective behavior. INTRODUCTION The capacity of an optical communication system can be increased using the Wavelength Division Multiplexing (WDM) technique [1]. Multiplex is the operation of combining several optical signals and transmit all of them along the same transmission medium. At the reception end it is necessary to carry out the reverse operation for separating the combined signal into each individual component, i.e., to demultiplex the signal. In this paper we report the use of an integrated photodetector and demultiplexer device based on two stacked mutilayered a-SiC:H/a-Si:H structures that act as optical filters in the visible range [2, 3]. The possibility of tuning the spectral device sensitivity is analyzed and discussed under reverse bias and using several optical bias conditions. The use of such light to soak the device induces different modulations of the electrical field along both front and back heterostructures, which amplifies or cuts specific wavelengths [4]. This enables the identification of the transmitted individual input channels and implements the demultiplexing operation in the visible spectrum, which is useful for short range applications. DEVICE OPERATION Configuration Fig. 1 shows the simplified schematic diagram of the structure of the device, that has in the front side a very thin pin photodiode based on a-SiC:H and on the back side a thick photodiode of a-Si:H. Both front and back photodiodes are coated with a transparent electrode (indium tin oxide – ITO) to allow photons to enter the device from the front and back sides. The a-SiC:H has a wider bandgap than a-S:H. Although the long wavelength photons are incident onto the front photodiode, they are not absorbed by a-SiC:H since the photon energy is less than the bandgap energy of a-SiC:H (Eg=2.1 eV). Photons pass through the a-SiC:H and become absorbed in the back photodiode (Eg=1.8 eV). On the other side, the short wavelength
Data Loading...
