Modulation Response of Twin Optically Coupled Diode Lasers

The modulation response of twin optically coupled diode lasers is investigated by modeling the dynamics of the system with a set of single mode rate equations. Steady states of the system are derived analytically or calculated numerically when an analytic expression is not easily available. The stability of the steady states is examined by using a linear stability analysis, which is also used in an algorithm that calculates the infinitesimal modulation response. The modulation response is also calculated by using a numerical method that directly integrates the rate equations. Typical parameters for an InGaAsP diode laser are used in the algorithms to investigate mutual coupling and evanescent coupling. It is discovered that mutually coupled lasers can be effectively modulated out to frequencies of approximately 9GHz compared to 4GHz for a solitary laser. Large regions of the parameter space for evanescent coupling produce unstable steady states, but this is remedied by introducing asymmetric DC currents through the lasers or by introducing the effects of gain saturation.