Study On The Characteristics Of External Cavity Semiconductor Lasers

In recent years, the external cavity semiconductor laser (ECSL), regarded as one of the candidate light sources of DWDM systems, has received considerable attention because of some good characteristics such as the narrow line-width, the easily controllable working wavelength, the temperature stability and low cost, etc. Even so, the instability sometimes accompanied by mode hoping and hysteresis of the lasing wavelength of the ECSL, and the instability of output power have been observed. 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, after taking into account the multiple reflections of light in external cavity, the influence of the optical feedback on the large signal modulation characteristics of the external cavity semiconductor laser (ECSL) has been theoretically investigated. The numerical simulations show that, when the optical feedback is strong or weak and the modulation index varies in the large range, the peak photon number of the ECSL exhibits single period, moreover the peak photon number of the ECSL increases monotonously with the increase of the modulation index; However, the peak photon number behaves single period, multi-period or chaos for different modulation index when the optical feedback is intermediate.