Any visible-spectrum application of ultrashort laser pulses must overcome a fundamental challenge: red light travels quicker through transparent materials like glass than blue light. As a result, when an ultrashort laser pulse passes through a glass lens, the tightly packed light wavelengths disperse, rendering the beam useless. For decades, optical experts have struggled with the problem of chromatic dispersion. The majority of today’s solutions include extra components that enhance the size and bulk of optical devices. Researchers have now created a silicon coating that can counteract the effects of dispersion when applied to the surface of a glass lens.
The method is adaptable to diverse spectrum regions and applications, leading to quick application in traditional optics and optical setups. The ultra-thin silicon coating consists of carefully engineered silicon pillars that capture and store red light for a brief period before re-emitting it. The slower-moving blue light can catch up thanks to this momentary halt.
The coating functions as a speed bump for the red light, averaging out the speed of each wavelength of light and counteracting the dispersive effects of transparent materials.