Integrated optical 4*4 star coupler on LiNbO3

A novel low-loss passive planar 4*4 star coupler consisting of four interconnected 3 dB couplers was fabricated on X-cut LiNbO3:Ti using Z-propagation. Almost even distribution was achieved for both TE and TM polarised light incident on any of the four inputs. Excess loss including fibre coupling was <4.2 dB.