The objective is to demonstrate the feasibility of the frequency stabilization of a Quantum Cascade Laser (QCL) and demonstrate the improvement of a stabilization loop with respect to passive stabilization.

The supra-THz (>3 THz) bands have been recently proposed for low Earth orbit THz remote sounding missions such as LOCUS (Low-Cost Upper-atmosphere Sounder). In order to achieve coherent detection, heterodyne receivers at supra-THz frequencies are under development by integrating in a single waveguide cavity a Schottky based mixers fed by a Quantum Cascade Laser (QCL) as Local Oscillator (LO). Thanks to the QCL, enough LO power is available to drive the mixer. Currently, a simple combination of passive thermal and electrical bias control is proposed for the frequency stabilization of the QCL. In order to achieve the frequency stability that would allow meeting the scientific requirements, phased lock loop systems such as the beating tone of two lasers injected into the QCL shall be investigated. The activity aims at proposing, manufacturing and testing a frequency stabilization loop for QCLs used as LO of supra-THz Schottky mixers. The activity consists in: - establishing the state of the art survey for the Schottky based supra-THz heterodyne receivers and QCL LO, - issuing the main mission, receiver and LO performance requirements including frequency stability. - performing trade off analysis and selecting one baseline frequency stabilization loop solution including its integration with the QCL and Schottky mixer. - designing and analysing the selected configuration. - manufacturing and testing the critical breadboard elements - proposing a roadmap and a development plan for the critical elements.