As a vocal trainer who expands the opera singer’s octave range, researchers from the National Institute of Standards and Technology (NIST) have nearly two-thirds expanded the frequency range in which a chip-scale device can generate and measure light wave oscillations with high accuracy. An extended range of the system, known as a micro-ring resonant frequency comb, or micro-comb, can improve greenhouse gas sensors and can also improve global navigation systems.
Gregory Mile and his colleagues from NIST, including team leader Kartik Srinivasan, along with staff from the United Quantum Institute (NIST-University of Maryland Research Partnership) and the University of Maryland, reported their results in a December 14, 2021 issue. The nature of communication.
The frequency crest acts as an optical variant of the ruler. Just as a ruler divided into hundreds of ticks at a known distance from each other measures an object of unknown length, the frequency crest contains hundreds of different ultra-sharp, evenly spaced frequency jumps to accurately measure light of unknown frequency (The tool is so named because frequency jumps resemble comb teeth.)
Over the past two decades, scientists from NIST and other research institutions have shown that microbes can play an important role in creating high-precision optical clocks, calibrating detectors that analyze stellar light to search for planets outside the solar system, and detecting traces of gases in the environment. .
One of the types of microcombs widely studied at NIST consists of a miniature rectangular waveguide, a channel that limits light waves, connected to a ring-shaped resonator about 50 micrometers in diameter (ppm). The laser light, which is introduced into the waveguide, enters the micro-ring resonator and goes around the ring.
Usually the circulating light begins to change in amplitude and can form different patterns. However, by carefully adjusting the laser, the light inside the micro ring forms a soliton – a single-wave pulse that retains its shape as it moves around the ring.
Each time the soliton completes one circle around the micro ring, part of the pulse separates and enters the waveguide. Soon a number of wave pulses fill the waveguide, and each wave in time is separated from the next by the same fixed interval – the time it took the soliton to pass one circle around the micro ring. The parade of wave pulses in the waveguide corresponds to one set of evenly spaced frequencies and forms the teeth of the frequency crest. The number and amplitude of the teeth are primarily determined by the size and composition of the ring, as well as the power and frequency of the laser.
Recently, NIST scientists wondered what would happen if they produced a microcomb using two lasers, each generating a different frequency of light, not just one. They found that through a complex series of interactions with soliton light circulating in the microring resonator, the second laser induced two new sets of teeth or evenly spaced frequencies that are copies of the original set of teeth but are shifted to higher and lower frequencies. The lower frequency set is in the infrared part of the spectrum, and the second – at much higher frequencies close to visible light. The comb also stores its original teeth at close infrared frequencies.
The extended microcomb range allows you to use many applications at different frequencies. The system is the first time researchers have created a stable microcomb that connects such a wide range of light frequencies, Srinivasan said.
In addition, the team found that by changing the frequency of the second laser, new sets of teeth can be easily converted to higher or lower frequencies regardless of the shape or composition of the microring resonator. This makes the system extremely versatile.
This can allow a single microcomb to measure the characteristic oscillations of atoms and molecules, including pollutants that both emit and absorb light over a wide range of frequencies, thus increasing the sensitivity of the detectors.
Wider coverage may also help further stabilization efforts microcomb, so that its traces remain fixed rather than slightly reflected from the original color set. Increased stability can stimulate the development of portable optics atomic clock accurate enough to be used outside the lab, leading to more accurate and precise navigation systems, Moyle said.
Gregory Moille et al., Kera’s ultra-wideband microcomb through spectral translation of a soliton, The nature of communication (2021). DOI: 10.1038 / s41467-021-27469-0
Citation: Scientists are significantly expanding the frequencies generated by the miniature optical ruler (2022, February 23) obtained on February 23, 2022 from https://phys.org/news/2022-02-scientists-greatly-frequencies-miniature-optical. html
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