Simple Silicon Coating Solves Long-Standing Optical Challenge for Powerful, Ultrafast Laser Pulses

Quick bursts of laser light, lasting less than a trillionth of a second, are used in a range of applications today. These ultrashort laser pulses have allowed scientists to observe chemical reactions in real-time, image delicate biological samples, build precise nanostructures, and send long-distance, high-bitrate optical communications. 

But any application of ultrashort laser pulses in the visible spectrum must overcome a fundamental difficulty — red light travels faster than blue light through transparent materials like glass. So, when an ultrashort laser pulse passes through a glass lens, the tightly packed wavelengths of light separate, destroying the usefulness of the beam.

This chromatic dispersion problem has plagued optical researchers for decades. Today, most solutions involve additional components that increase the size and bulk of optical devices. 

Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), in collaboration with Graz University of Technology,  have developed a silicon coating that, when applied to the surface of a glass lens, can counteract the effects of dispersion.