Multi-Frequency, Tunable Terahertz Quantum Cascade Laser Source

Significantly increases available frequency channels for imaging, sensing, and spectroscopy

https://technology.nasa.gov/patent/LEW-TOPS-86

Glenn's new technology allows broader use of frequencies with quantum cascade lasers, such as the one above

Innovators at NASA's Glenn Research Center have developed a cutting-edge tunable, multi-frequency controller for a terahertz (THz) quantum cascade laser (QCL) source. This novel device enables use of the full bandwidth of broadband THz, producing an extensive number of frequency channels. Operating at THz frequencies, QCL emissions deliver higher-resolution imaging than microwaves, and they provide higher-contrast images than X-rays. Previous approaches to tuning the emission from a THz QCL source have been unsatisfactory, whether because of a limited numbers of tuning channels, high cost, high complexity, or frequency instability. Glenn's scientists have devised an efficient technique that generates high-resolution tuning over a vast number of usable THz-frequencies, at commercial levels of cost and simplicity. This innovation opens a pathway to vastly expanded use of THz QCL in unprecedented terrestrial applications, including communications, homeland security screening, biomedicine, and quality control.

Benefits

·                                 Versatile: This tunable source provides higher resolution (more single-mode) frequency channels in the THz range, giving developers access to a greater number of applications

·                                 Cost-effective: Fewer components and reduced size and weight offer savings compared to other approaches to tuning THz QCL emissions

·                                 Safer: THz frequencies are non-ionizing and therefore harmless to living tissue

·                                 Reliable: Accurate and reliable tuning eliminates the need for cryocoolers, heatsinks, stabilization platforms, or other components that limit temperature fluctuations and vibration

Applications

·                                 Homeland security screening to detect concealed weapons or explosives

·                                 Biomedical imaging

·                                 Manufacturing, quality control, and process monitoring

·                                 Wireless communications

·                                 Remote sensing of environmental pollutants in the atmosphere

·                                 Imaging systems within semiconductors

·                                 Spectroscopy and tomography

The Technology

THz occupies the frequency gap between microwaves and infrared light waves. THz produces a frequency that is both coherent and spectrally broad, so such images can contain far more information than a conventional image formed with a single-frequency source. Although THz frequency can penetrate fabrics and plastics, it is non-ionizing and therefore harmless to living tissue or DNA, making it very valuable for imaging and screening applications. Scientists have attempted to find practical ways to use a QCL as a tunable source for THz frequencies for a variety of applications, but until now, have been unable to overcome obstacles in cost and fabrication.

Glenn's innovation is a THz QCL source (range 1 to 5 THz) based on a passive waveguide tuning mechanism that can use the full bandwidth of a broadband THz QCL and produce a vast number of frequency channels. In Glenns process, a tunable QCL is coupled to a grating router, which consists of an appropriately configured linear dielectric array. The grating router receives a THz frequency from the QCL and generates a high density of THz frequencies. The output of the grating router enters an on/off switching waveguide controller, which is configured to select one desired THz frequency. This desired frequency is then fed into a waveguide multiplexer, which combines the output ports of the controller into a single signal for transmission. Glenn's novel technology unlocks the potential for THz frequencies to revolutionize sensing and imaging applications across a wide range of industries. 

This is an early-stage technology requiring additional development, and Glenn welcomes co-development opportunities.