摘要： Interband cascade lasers (ICLs) are power-efficient mid-infrared laser sources for applications in sensing of numerous molecules and in free-space optical communications. The static performances of ICLs including the lasing threshold and the output power have been significantly improved since its first demonstration by R. Yang [1]. GaSb-based ICLs have optimal performance in the spectral range of 3-4 μm, which is hard to reach for the quantum cascade laser counterpart [2]. This work proposes a rate equation model for studying dynamical characteristics of ICLs including the intensity modulation (IM) response, the relative intensity noise (RIN), and the frequency noise (FN). Taking into account carrier dynamics in the W-shape active region while ignoring those in the electron and hole injectors [3], the rate equations for the carrier number N, the photon number S, and the phase φ of the electric field read. Based on the standard small-signal analysis of the above rate equations, we obtain analytical formulas for IM response, RIN, and FN, respectively (not shown in this paper). The inset of Fig. 1(a) shows that ICLs exhibit an underdamped resonance peak in the IM response at a low pump current, and the modulation bandwidth increases with increasing pump current as conventional laser diodes. Figure 1(a) proves that more gain stages are desirable for enhancing the modulation bandwidth of ICLs. The inset of Fig. 1(b) shows that the RIN is raised at the resonance frequency, while a small stage number reduces the RIN in the whole spectral range. Figure 1(b) demonstrates that the RIN at the low-frequency range (<1.0 GHz) increases nonlinearly with the gain stage number. The inset of Fig. 1(c) shows that the FN of ICLs is raised at the resonance frequency, while a small stage number reduces the FN in the whole spectral range as well. The intrinsic spectral linewidth of ICLs in Fig. 1(c) is obtained from the low-frequency FN level. It is found that the intrinsic linewidth linearly increases with the gain stage number, which is consistent with the derived analytical formula. In summary, we theoretically prove that a large gain stage number is desirable for enhancing the modulation bandwidth, while a small stage number is favorable to reduce both the RIN and the FN/linewidth of ICLs.