I Ain't Afraid of No Hyperspectral Terahertz Ghost Imaging

One of the fun things about scientists is the way that they are excited by stuff that makes everyone else go, "huh?" The above technique, described in this article by Belle Dumé, is probably a good example. I imagine that more than 9 in 10 people frown at the phrase "Hyperspectral Terahertz Ghost Imaging" and say to the people who are celebrating it, "Hey, good for you!" and hope very strongly they don't explain it.

But I'll give it a shot. As the article notes, "Terahertz" (THz) describes an electromagnetic wavelength -- in other words, radiation. It passes through substances that block visible light but it's less energetic than Xrays so much less likely to damage living tissue. And it has another advantage in that it shows the electromagnetic spectrum of the substance being imaged -- which earns it the label "hypespectral." That's cool for scientists because spectral analysis tells them what something is made of. Imagine a selfie that could show what chemicals and molecules made up someone's skin, for example.

But it turns out that a lot of the details scientists want to study are smaller than the THz wavelength, which means that they don't show up on an THz images. The THz waves kind of skip right over them. When scientists would try to focus the waves to get these small details in their images, then the increased energy would change them -- sort of like how an object may look different depending on what color of light is shined on it. In the same way that a viewer couldn't see the real color of that object, the scientists doing THz imaging wouldn't see what their subjects really looked like. They might get the image, but they would destroy the electromagnetic spectrum that showed them what the object was made of.

This is where "ghost imaging" comes in. If I read Dumé's article correctly, then the project team led by photonics professor Marco Peccianti uses a combination of lasers and THz wavelengths and via computer algorithm sort of swaps one for the other so the image produced has extremely fine detail and the full electromagnetic spectrum. It's similar to ultrasound imaging, where a computer translates the results of high frequency sounds aimed at a target object into an image even though no electromagnetic radiation ever passes through the target.

When perfected, the technique could allow a medical team to electromagnetically biopsy a tumor without any surgery, or chemically analyze samples without altering them. Which would be pretty cool and is probably a good reason to be excited if you work in photonics, even if no one around you knows why you're so giddy.