The QuaLIDAD Project starts from the studies on Quantum Cascade Lasers (QCLs) performed within the EU Qombs Project. In Qombs, QCLs have been studied as emitters of low-phase-noise mid-infrared (IR) radiation for open-field communication and innovative LIDAR (LIght Detection And Ranging) schemes. The QuaLIDAD Project aims to exploit these results by developing a new compact and portable LIDAR system for remote in-field sensing of air pollution and range finding.
In its traditional implementation, a LIDAR retrieves range-resolved information by using pulsed visible or near-IR laser sources, with high peak power and short duration, through time resolved detection of the return signal. Our idea is to move the LIDAR operation in the mid-IR region, using continuous-wave QCLs operated with the Pseudo-Random Modulation (PRM) technique.
Moving at long infrared wavelengths has a double motivation. At first, mid-IR radiation is less affected by particle backscattering than radiation at shorter wavelengths, and this allows to solve the problems of poor operation under low-visibility conditions, e.g. related to the presence of fog, smoke, dust and other effects degrading the vision at short wavelengths. At the same time, the presence of atmospheric high-transparency windows allows the beam to propagate over long distances. Second, the mid-IR is the molecular fingerprint region, and the presence of strong absorptions from many pollutant molecules makes the system suitable also for air quality analysis.
Given this variety of applications, a mid-IR LIDAR can have a strong impact on society, from security and self-driving systems to air quality analysis, environmental control and athmospheric studies.
The final goal of the Project is the development and test of a portable LIDAR prototype working in the mid-IR spectral region, based on a cw QCL and on the PRM technique. This has been achieved by the following steps:
- design and acquisition of the optical components, in particular the laser, the detector and the required collimating and focusing optics;
- design, development and test of custom electronic Control Unit, capable of driving the QCL with a high-frequency PRM code, and including a digital comparator for the collected signal and a storage unit for the acquired data;
- setup of the LIDAR system, characterization and test of the PRM code, validation of the LIDAR with laboratory tests and outdoor measurements.
