Credit: G. Mathews/University of Colorado Boulder
A team of researchers from the National Institute of Standards and Technology (NIST), Toptica Photonics AG, and the University of Colorado Boulder have developed a frequency comb that can detect specific molecules every 20 nanoseconds within a sample. The development increases the potential applications of frequency combs, a laser system, that previously was hindered by their detection speed.
The research, published in Nature, paves the way for utilizing frequency combs to research the intermediate steps in rapid processes. The researchers utilized a dual-frequency comb setup which traditionally employs a dual femtosecond laser configuration. However, researchers chose a simpler and more cost-effective electro-optic comb which utilizes a single beam of light that is then split into two. The beams are then altered by an electronic modulator that shapes the beams into “teeth”, thus creating the frequency comb.
Traditional frequency combs contain millions of “teeth”, however, the comb developed by the researchers only had 14. As a result of the reduced number of teeth, each tooth had higher optical power and was further apart in frequency resulting in a strong signal that could detect changes at the 20 nanosecond timescale.
"In a more complicated system like an aircraft engine we could use this approach to look at a particular species of interest, such as water or fuel or CO2, to observe the chemistry. We can also use this approach to measure things such as pressure, temperature or velocity by looking at changes in the signal," said NIST research chemist David Long
Another unique component of the comb was the parametric oscillator which can shift the teeth from the near-infrared to mid-infrared colors absorbed by CO2. This oscillator can also be used to tune to other regions of the mid-infrared allowing researchers to detect other molecules within that region.
"What is truly special about this work is that it substantially lowers the barrier to entry for researchers who would like to use frequency combs to study fast processes," said co-author Greg Rieker, a professor at the University of Colorado Boulder
"With this setup, you can generate any comb you want. The tunability, flexibility and speed of this method open the door to lots of different types of measurements," added Long.