Some very clever researchers wanted a sensitive, fast spectrometer — an instrument that measures how much light of which wavelength arrives at the sensor. We have that technology: as creatures that see visible light, we’ve developed a lot of technology for visible light.
But instead of taking a look at the wavelengths in visible light, they wanted to look at near-infrared light. And that problem gets a little trickier, although there are spectrum analyzers and other instruments designed just for such purposes.
But these guys at Stanford University and the National Institute of Informatics in Tokyo used a nonlinear optical material, called periodically-poled lithium niobate, to convert the (relatively) low-energy infrared photons into higher-energy red photons, which could then be sensed in the visible by exquisitely sensitive detectors.
Nonlinear optical materials, or NLOs, are very very cool materials that (under precise conditions) can do tricks with light that normal materials just can’t — tricks like changing the color of light. I tend to think that light is pretty magnificent and spiffy just in general, but with NLOs, you can make it jump through hoops, too!
What they ended up with was a spectrometer about 100 times more sensitive than the instruments currently used for measuring the spectrum of near-IR wavelengths! And that’s pretty cool!
(More details in an Optics Express paper. The OSA journal, Optics Express, offers free access — so anyone can read it.)
Also, I’m pretty sure that the almost-Company-logo-like detail in the picture is a coincidence. Pretty sure…