Numerical Investigation on the Temperature dependent Impedance Characteristics of Far-Infrared Quantum Cascade Lasers

Quantum Cascade Lasers (QCLs) as Terahertz (THz) frequency sources offer a potentially viable solution for new applications in mid and far-infrared frequency bands. This research work exhaustively investigates the temperature dependence on the impedance of temperature dependent Quantum Cascade Lasers (QCLs) operating at 116μm, for the first time. In the 90-stage QCL considered for the work, the cold finger temperature is varied from 15K to 45K. When the device is biased at 0.6A current along with a cold finger temperature of 45K, the magnitude of intrinsic impedance was found to be 23.91mΩ, at a frequency of 4GHz. As the cold finger temperature is increased from 15K to 45K, the impedance response of the device becomes flat and stays constant. At 45K with an injected current of 1.5A, maximum impedance of 3.1mΩ is obtained. The resonant frequency characteristics of the device increase with increase in injected current and cold finger temperature. Also, it is observed that the magnitude of intrinsic impedance decreases with increase in injected current. The impact of cold finger temperature on the intrinsic impedance characteristics are detailed for prospective Radio over Fiber (RoF) applications.