A tiny laser-heated, silicon-tipped fiber-optic device designed by researchers from the U.S. Naval Research Laboratory and University of Nebraska-Lincoln can approach 2,000 F (1,093 C), and go from room temperature to 300 degrees in fractions of a second. The tip of the device is only 100 µm in diameter and, depending on the version, 10 or 200 µm long.

The device’s heating capability could find application in monitoring greenhouse gases, prepping specimens for biological research, or producing micro-bubbles for medical or industrial applications. It also acts as a thermometer whose performance at extreme heat would allow it to monitor temperature in the demanding environments of engines and power plants.The paper-thin device goes from room temperature to white-hot. (Optics Letters / Guigen Liu)

A previously engineered fiber-optic temperature sensor suitable for oceanography also featured a microscopic silicon pillar attached to the end of fiber-optics – flexible glass strands that transmit light signals at extreme speeds. However, the glue that bonded the silicon and fiber-optics would soften at roughly 200 F (93 C), restricting its use at higher temperatures.

Building on this experience, the researchers used an extremely hot arc of electric current – essentially a sustained bolt of lightning – to fuse another fiber-optic strand with the opposite side of the pillar. The process simultaneously softened the glue on the other side and detached the original fiber-optic strand, leaving just the newly fused device.

Two wavelengths of light were then fed through the fiber-optic – one a 980-nmr laser that gets absorbed by the silicon, the other a 1550-nm wavelength that passes through it.

Because the absorbed laser produces heat, its remote-controlled power dictates the temperature of the device. The broader wavelengths that enter the silicon get partially reflected by the two ends of the pillar, which functions as an interferometer that allows temperature measurement.