Novel device to enhance applications ranging from security screening to chemical sensing

May 19th, 2008 - 4:37 pm ICT by admin  

Washington, May 19 (ANI): Engineers have demonstrated the first room-temperature electrically-pumped semiconductor source of coherent Terahertz (THz) radiation (T-rays), a novel device that could greatly enhance applications ranging from security screening to chemical sensing.

Demonstrated by engineers and applied physicists from Harvard University, this breakthrough in laser technology, based upon commercially available nanotechnology, has the potential to become a standard Terahertz source.

Using lasers in the Terahertz spectral range, which covers wavelengths from 30 to 300 amperes, has long presented a major hurdle to engineers. In particular, making electrically pumped room-temperature and thermoelectrically-cooled Terahertz semiconductor lasers has been a major challenge.

These devices require cryogenic cooling, greatly limiting their use in everyday applications.

By contrast, our device emits T-rays with several hundreds of nanowatts of power at room temperature and microwatts of power at temperatures easily achievable with commercially available thermoelectric coolers, said research associate Mikhail Belkin from Harvards School of Engineering and Applied Sciences.

Further, there is the potential of increasing the terahertz output power to milliwatt levels by optimizing the semiconductor nanostructure of the active region and by improving the extraction efficiency of the terahertz radiation, he added.

To achieve the breakthrough and overcome the temperature limitations of current laser designs, the researchers engineered a room temperature mid-infrared Quantum Cascade Laser (QCL) that emits light at two frequencies simultaneously.

The generation of Terahertz radiation occurs via the process of difference-frequency generation inside the laser material at room temperature at a frequency of 5 THz.

The compact millimeter length semiconductor lasers operate routinely at room temperature with high optical powers and are increasingly used in the commercial sector for wide range of applications in chemical sensing and trace gas analysis.

The devices, made by stacking ultra-thin atomic layers of semiconductor materials on top of each other, are variable and tunable, allowing an engineer to adjust the energy levels in the structure to create an artificial laser medium.

Terahertz imaging and sensing is a very promising but relatively new technology that requires compact, portable and tunable sources to achieve widespread penetration, said Federico Capasso from Harvards School of Engineering and Applied Sciences.

Our devices are an important first step in this direction, he added.

The ability of Terahertz rays to penetrate efficiently through paper, clothing, cardboard, plastic and many other materials makes them ideal for use in many applications.

For example, a device emitting T-rays could be used to image concealed weapons, detect chemical and biological agents through sealed packages, see tumors without causing any harmful side effects, and spot defects within materials such as cracks in the Space Shuttles foam insulation. (ANI)

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