We propose and describe a new configuration for splitting and combining operations of high-speed amplitude-modulated optical signals between the two interacting beams by using two-wave mixing in photorefractive Cu-doped (K0.5 Na0.5)0.2 (Sr0.61 Ba0.39)0.9 Nb2O6 (Cu-KNSBN) crystal. These operations are simultaneously achieved by changing the intensity ratio of the two incident beams. We also apply this scheme to a photorefractive pulse shaping in the time domain that consists of two amplitude-modulated beams that are coupled automatically through two-beam interactions in the crystal. Some preliminary experimental results are presented and discussed.

In this paper, we propose a new algorithm of enhancing covariance matrix estimate to be used for estimating the directions-of-arrival (DOAs) of multiple incoherent signals incident on a uniform circular array. The underlying covariance matrix possesses a special theoretical property such as having spatial stationarity. The proposed enhancement approach based on the use of this property is found to provide improved DOA estimates in comparison to the unenhanced MUSIC for narrowband incoherent signals.