Regular papers

All-optical modulation in a CMOS-compatible amorphous silicon-based device

¹ Department of Information Science, Mathematics, Electronics and Transportations (DIMET) Università degli Studi “Mediterranea”, Via Graziella Località Feo di Vito, Reggio Calabria, 89060, Italy
² Institute for Microelectronics and Microsystems – Consiglio Nazionale delle Ricerche (IMM-CNR) Unit of Napoli, Via P. Castellino, 111, 80132, Napoli, Italy

^* sandro.rao@unirc.it

Received: 6 December 2011
Revised: 29 January 2012

Abstract

Active silicon photonic devices, which dynamically control the flow of light, have received significant attention for their use in on-chip optical networks. High-speed active silicon photonic modulators and switches rely on the plasma dispersion effect, where a change in carrier concentration causes a variation in the refractive index. The necessary electron and hole concentration change can be introduced either by optical pumping, or by direct electrical injection and depletion. We demonstrate a fast photoinduced absorption effect in low loss hydrogenated amorphous silicon (a-Si:H) waveguides deposited at a temperature as low as 190°C. Significant modulation (M_% ∼90%) occurs with a 1 mm-long device. We attribute the enhanced modulation to the significantly larger free-carrier absorption effect of a-Si:H. The complementary metal-oxide semiconductor (CMOS) compatible technology of a-Si:H could be considered as a promising candidate to enable an easy back-end integration with standard microelectronics processes.