A "Trapped Rainbow" Could Hold The Key To Cloaking

The possibility of invisibility cloaks is becoming more and more of a reality. Scientists have managed to cloak a silicone thread by coating it with gold and canceling out the two compounds' respective frequencies. Even more recently, a team of researchers from Towson University and the University of Maryland have created 25,000 miniature invisibility cloaks that slow down and even trap light, creating a "trapped rainbow."

The cloaks are 30 micrometers in diameter and are laid out on a 25 millimeter gold sheet.

The tiny cloaks each contain a microlens that bends light around itself, which was coated in a gold film. They were then laid face down on a glass slide also coated with gold and subjected to a series of tests from a laser. The light has to travel around the lens, and through increasingly narrow gaps, making the light slow down or even stop.

The researchers hope that this could have practical medical purposes, because trapped light is slower and interacts more strongly with molecules. Through a process known as fluorescence spectroscopy, biological material can be identified based on the amount of light that they absorb, and then emit.

"The benefit of a biochip array is that you have a large number of small sensors, meaning you can perform many tests at once. For example, you could test for multiple genetic conditions in a person's DNA in just one go," says Dr Vera Smolyaninova, the lead author.

There are still hurdles to overcome, and the design isn't perfect. In its current state, the array worked very well when the laser beam was shone along the rows. However, when the laser beam was shone at different angles, imperfections became clearly visible.