Scientists use gold to improve microlaser technology

By attaching gold nanoparticles to the surface of a microlaser, scientists at the University of Southern California Viterbi School of Engineering demonstrated that it is possible to create frequency combs that take up less space and require 1000 times less power than current industrial comb technology.

Frequency combs are large and highly energy-consuming devices that can create a rainbow of light from a single colour and are generally used to improve cybersecurity, GPS systems and the detection of toxic chemicals.

In order to create systems that could enable residential or portable applications, the USC researchers decided it was important to figure out how to reduce both the size of the device and the power requirements for wavelength generation. They found their answer in gold specks 1/100,000 the size of a human hair.

By attaching gold nanorods to the surface of a single microlaser, the research team led by Andrea Armani, a professor in the Mork Family Department of Chemical Engineering and Materials Science, was able to run lab tests which showed that frequency combs can function with only milliwatts of input power, which decreases the system’s footprint and takes the technology from the lab to real-world applications.

The way it works is that the interaction of the light from the microlaser with the gold particles results in many additional wavelengths being generated, a process that is further improved by a polymer coating on the nanoparticles.

“The role of the gold nanorods is to increase the intensity of the light circulating in the device,” co-lead author Vinh Diep said in a press release. “The higher-intensity light can then interact with organic molecules on the surface of the gold to generate other wavelengths of light. This combined effect allows for the comb generation to begin at a much lower power than the traditional pulsed-laser approach.”

Diep also explained that by using the gold nanorod coating, they observed a comb that can span over a wavelength range of 300 nanometers. Without the gold nanorods, a comb could not be generated at the same power.

“Demonstrating a large range shows the device’s strong potential for applications in developing a portable chemical spectroscopy system, where the chemical signal only occurs at a specific wavelength, and the accuracy is dependent on the light source,” the group of researchers concluded.