Noise assisted binary information transmission in vertical cavity surface emitting lasers

Abstract

Summary form only given. Vertical cavity surface emitting lasers (VCSELs) are becoming very important optoelectronic communication devices. VCSELs can be used for the transmission of binary signals by modulating the pump current between two values which correspond to a high (1) and a low (0) output intensity level. However, they present some peculiar features: namely the emission in several transverse modes and polarization fluctuations. In some critical current. Regions, these lasers can emit indifferently in two different states of polarization and/or transverse pattern for the same value of the pump current. The laser dynamics in such narrow bistable regions is characterized by noise-induced jumps between the two emission states. A polarization and/or a spatial filter allows one to observe the random jumps as light intensity hops. We evidence a novel phenomenon which is observed in these conditions, that we have called noise assisted binary information transmission (NABIT): the addition of noise to the pump current up to an optimal value leads to a strong improvement of the transmission quality, measured by the bit error rate (BER). The phenomenon is similar to stochastic resonance, which has been recently observed and characterized in VCSELs.