Researchers use a new frequency comb to capture photon high-speed processes

From detecting COVID in respiration to monitoring greenhouse gas concentrations, laser technology called frequency combs can recognize specific molecules as simple as carbon dioxide to as complex as monoclonal antibodies, with unparalleled accuracy and sensitivity. Although frequency combs have incredible capabilities, their ability to capture high-speed processes such as hypersonic propulsion or protein folding into final three-dimensional structures is limited.

The National Institute of Standards and Technology (NIST), Toptica Photonics AG, and the University of Colorado at Boulder have now established a frequency comb system that can identify the presence of certain molecules in samples every 20 nanoseconds or billionths of a second.

Researchers may be able to use frequency combs to better understand the instantaneous intermediate steps in rapid movement, from the mechanics of hypersonic jet engines to the chemical reactions between enzymes that use this new function to regulate cell growth. The research results were published by the research team in the journal Nature Photonics.

The researchers used the commonly used dual frequency comb arrangement in their experiment, which consists of two laser beams that work together to detect the color spectrum of molecular absorption. Most dual frequency comb configurations use two femtosecond lasers to synchronously emit a pair of ultrafast pulses.

In this new experiment, researchers used a simpler and cheaper device called an "electro optical comb", which divides a continuous beam of light into two beams. Then, the electronic modulator changes the beam of light, generating an electric field, shaping them into a single "tooth" of a frequency comb. Each tooth represents a different color or frequency of light that can be absorbed by molecules of interest.

In a typical trial run, the electro-optical comb used by the researchers only contained 14 teeth, while the traditional frequency comb had thousands or even millions of teeth. However, researchers were able to detect changes in light absorption on a time scale of 20 nanoseconds, as each tooth has higher light power and is spaced apart from other teeth in frequency.

Researchers used a small nozzle in an inflatable cylinder to measure the pulse of supersonic carbon monoxide 2 when they appeared for demonstration. Measure the content of carbon dioxide in the air, or the proportion of CO2 mixture. Researchers can determine the concentration of pulse motion 2 by observing changes in carbon monoxide.

Scientists have observed how carbon monoxide reacts with the atmosphere in Mode 2, resulting in a change in atmospheric pressure. Even with state-of-the-art computer simulations, it is difficult to accurately extract these details.

The data collected from these studies can shed light on how to better understand how greenhouse gases interact with climate or lead to the design of internal combustion engines.

In the setup, an optical parametric oscillator was used to shift the comb teeth from near-infrared color to mid infrared color absorbed by carbon monoxide. However, the optical parametric oscillator can be set to various parts of the mid infrared spectrum, allowing the comb to detect different substances that absorb light in these areas.

This study includes information that other researchers can utilize to develop similar systems in the laboratory, making this new technology publicly available in a wide range of research fields and industries.

Long pointed out, "With this setting, you can generate any comb you want. The adjustability, flexibility, and speed of this method open the door to many different types of measurements.

Source: Laser Network