Transfer Matrix Model Of The Fiber Grating External Cavity Semiconductor Laser

In recent years,with the rapid development of the optical communication and the improvement of the point-to-point transmission system,the large-capacity and long haul-dense wavelength division multiplexed(WDM) transmission technologies have been rapidly developed,which put forward new requirement for the semiconductor lasers.However,the conventional semiconductor lasers have some disadvantages such as mode hoping,temperature instability and poor linearity,which limited the further development of the communication system.A fiber Bragg grating as an external feedback component in the external cavity semiconductor laser(ECSL) has been considered as one of the most effective methods for realizing the narrow line-width, the easily controllable working wavelength and the temperature stability,etc.Therefore, the characteristics of ECSL should be studied farther to acquire the coherent light source with more accurate and stable lasing wavelength.In this paper,the characteristics and operation principles of the ECSL and the fiber Bragg grating have been introduced.Then based on the coupled mode theory,the transfer matrix model of the fiber grating external cavity semiconductor laser(FGECSL) has been established.According to this mode,the active region,passive region and. grating of the FGECSL has been treated as an integral system,after taking into account the joint contribution of semiconductor laser,external cavity and fiber grating to the phase condition,the mode distribution of the FGESCL can be determined.As a result, the effect of the FG external cavity length on the lasing wavelength of the FGESCL is investigated theoretically.Finally the output spectrum of the FGECSL has been investigated depended on the steady-state multimode rate equations.The results can provide instructive insight in to the characteristics of FGECSL.