Microwaves from Silicon Chips

X-rays are widely used for medical imaging and security, but they still are dangerous. Would it be possible to replace X-rays by an imaging technology based on microwave radiation? Until now, it was not feasible because portable devices were not powerful enough. Now, two U.S. scientists have found how to make microwaves on a chip to replace X-rays for medical imaging and security. Their new method is based on a phenomenon known as nonlinear constructive interference. With this method, it is possible to generate high-power signals at frequencies of 200 GHz and higher on ordinary silicon chips. This technology might be used in a few years by physicians to detect skin cancer or by airport security personnel to find objects hidden under clothing.

First, what is linear constructive interference? You can see it on the illustration on the left. The top part shows that it “occurs when two signals in phase combine to form a new signal whose amplitude is the sum of the two sources. The bottom part of the picture shows that “in a square lattice designed to create nonlinear interference, low-power signals from the bottom and side combine many wave peaks into one with a much higher amplitude.”

This method for generating high-power signals at frequencies of 200 GHz and higher on silicon chips has been developed by Ehsan Afshari, Cornell assistant professor of electrical and computer engineering, who is the rincipal investigator of Cornell’s Ultra high-speed Nonlinear Integrated Circuit lab (UNIC). He worked with Harish Bhat, assistant professor of mathematics at the University of California-Merced.

Source: Optical Society of America