14 DAY TRIAL // Improving security systems and national defense capabilities is a constant effort at Arizona State University (ASU). Investigators here have recently taken an important step forward in creating a new infrared photodetection technology, which may have important, large-scale applications.
The new technique could be used for a variety of purposes, such as improved body scanners, more capable medical imaging devices, consumer products and other commercial uses.
Security systems will undoubtedly stand to gain most from this innovation, which basically produced a new way of using infrared wavelengths for various forms of imaging. The study is detailed in a recent issue of the esteemed journal Applied Physics Letters.
Detecting infrared wavelengths is not always easy, and creating sensitive detectors can sometimes prove to be very difficult. What the ASU group did in the new study was show that arranging the atomic-scale structure of specific materials in certain ways could lead to more effective detection.
The detector the team created is made up of multiple layers of an advanced mixture of materials. Each of these layers is extremely thin – only nanometers thick – and contains numerous crystals. The material that results from combining multiple layers is generically called a superlattice.
Superlattices are wavelength-specific, meaning that the type and arrangement of materials making them up determines the portion of the electromagnetic spectrum they will see. Generally, sensors are made of a single type of superlattice.
Each photodetector works by using crystals to absorb various forms of light, and then converting it into an electrical signal. As such, the crystals' conversion efficiency is the factor that ultimately determines the sensitivity of the entire system.
ASU electrical engineer Yong-Hang Zhang explains that the quality of the overall detection is also largely dependent on this measure. The expert is based at the university's School of Electrical, Computer and Energy Engineering.
The group is using indium arsenide and indium arsenide antimonide to create superlattice structures that are extremely effective at converting infrared wavelengths to electrical signals. ASU scientists say that their sensors are significantly more capable of picking up these wavelengths than anything on the market today.