Studies On Polarization Switching Performance Of VCSEL Subjected To Optical Pulse Injection

In recent years,vertical—cavity surface—emitting lasers(VCSELs) have aroused great interest amongst scientists and enterprises in China and abroad.As a new kind of'semiconductor laser, VCSEL have such merits as low threshold,working in single longitudinal mode,small angle of divergence,high dynamic modulating frequency,easily implemented two-dimension integration than conventional edge emitting lasers.VCSEL have a significant implication prospect in optical communication,optical interconnection,image signal processing,etc.With its increasing application, the research of VCSEL's optical output characteristic becomes very important.Since VCSEL normally are symmetric in structure,the polarization of the fundamental transverse mode in VCSEL is generally not fixed.Near the threshold current,VCSEL normally operate in one linearly polarized fundamental transverse mode.When the bias current is increased, the polarization often switches to the orthogonal polarization.The optical injection from an external source of light may help to control or stabilize the VCSEL polarization and its study is interesting both from the point of view of dynamical instabilities and for applications in high density optical storage and optical signal processing.Based on the rate equations describing master and slave vertical cavity surface emitting laser (M-VCSEL,S-VCSEL),under the modulation of pulse biased current,the polarization characteristics of M-VCSEL output and the polarization switching performance of S-VCSEL subjected to optical pulse output from the M-VCSEL have been investigated.The results show that a periodical pulse c,an be obtained by adding a periodical pulse current on the M-VCSEL;under injection of the optical pulse from M-VCSEL,the output power of S-VCSEL will switch periodically between two orthogonal polarizations,and the period is equal to the period of the modulated current in M-VCSEL;through changing the modulated amplitude of current in M-VCSEL,the orthogonal polarization suppression ratio(OPSR) can be controlled easily.