High frequency modulation of mid-infrared quantum cascade lasers embedded into microstrip line

In this work, we have studied the frequency response to a direct current modulation of a mid-infrared quantum cascade laser that has been monolithically integrated within a microwave strip. By merging microwave and semiconductor laser technologies, we have demonstrated a flat frequency response up to ∼15 GHz for a device operating at 77 K and emitting at 9 μm. Laser performances are preserved and comparable to state of the art devices. Finally, in our devices, we have observed that the modulation bandwidth varies substantially upon the laser photon density. Improved frequency response is indeed achieved, while lasers operate well above threshold.