A team of researchers from Boston has developed a new terahertz radiation source with coveted frequency adjustment capability based on quantum cascade laser systems (QCL). Such a laser system has a compact size and it allows the development of futuristic communications, security, biomedical, and astronomical imaging systems.
It should be noted that terahertz electromagnetic frequencies emitted by fiber lasers have been widespread for their range of applications because these laser systems offer such advantages as high bandwidth, high resolution, long-range sensing, and the ability to visualize objects through materials. Nevertheless, the costliness, bulk, inefficiencies, and lack of tunability of traditional terahertz laser beam sources have limited growing markets.
Thus, this new combined terahertz laser beam emitter promotes future technologies from T-ray imaging in airports and space observatories to ultrahigh-capacity wireless connections. To be more precise, current fiber laser systems are considered to have limited tunability (less than 15 to 20% of the main frequency), that is why terahertz radiation is rarely used.
The researchers confirm that the new laser system helps open up this spectral region resulting in a revolutionary impact. The laser technology is based on a compact tunable semiconductor laser system, the quantum cascade laser (QCL) that is frequently used for chemical sensing and trace gas analysis. The thing is that the QCL laser system emits mid-infrared light, herewith, in this spectral region, most gases (low concentrations of molecules) can be determined by their specific absorption fingerprints.
According to researchers, “Terahertz waves could be emitted with high efficiency from gas molecules held within cavities much smaller than those currently used on the optically pumped far-infrared (OPFIR) laser system — one of the earliest sources of terahertz radiation”.
Nevertheless, the OPFIR laser systems are similar to all traditional terahertz laser beam sources, that is why they are regarded as inefficient with limited tunability. The change of the OPFIR laser on the quantum cascade laser system significantly increases the terahertz tuning range, therefore, the developed laser module has wider tunability now.
This laser system has been already tested and demonstrates the opportunity to tune the terahertz output to emit 29 direct laser beam transitions between 0.251 and 0.955 THz. The laser technology is universal, and it can be used to detect different gases. It is planned to use the developed laser system to observe skyward and determine unknown spectral features in the terahertz region.
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