Researchers demonstrate record speed with advanced spectroscopy
technique
Fast, sensitive dual-comb spectroscopy could be used for fast
measurements of fast and non-repeatable events

Date:
September 16, 2020
Source:
The Optical Society
Summary:
Researchers have developed an advanced spectrometer that can acquire
data with exceptionally high speed. The new spectrometer could
be useful for a variety of applications including remote sensing,
real-time biological imaging and machine vision.



FULL STORY ========================================================================== Researchers have developed an advanced spectrometer that can acquire data
with exceptionally high speed. The new spectrometer could be useful for
a variety of applications including remote sensing, real-time biological imaging and machine vision.


========================================================================== Spectrometers measure the color of light absorbed or emitted from
a substance.

However, using such systems for complex and detailed measurement typically requires long data acquisition times.

"Our new system can measure a spectrum in mere microseconds," said
research team leader Scott B. Papp from the National Institute of
Standards and Technology and the University of Colorado, Boulder. "This
means it could be used for chemical studies in the dynamic environment
of power plants or jet engines, for quality control of pharmaceuticals
or semiconductors flying by on a production line, or for video imaging
of biological samples." In The Optical Society (OSA) journal Optics
Express, lead author David R.

Carlson and colleagues Daniel D. Hickstein and Papp report the first
dual-comb spectrometer with a pulse repetition rate of 10 gigahertz. They demonstrate it by carrying out spectroscopy experiments on pressurized
gases and semiconductor wafers.

"Frequency combs are already known to be useful for spectroscopy,"
said Carlson. "Our research is focused on building new, high-speed
frequency combs that can make a spectrometer that operates hundreds of
times faster than current technologies." Getting data faster Dual-comb spectroscopy uses two optical sources, known as optical frequency combs
that emit a spectrum of colors -- or frequencies -- perfectly spaced
like the teeth on a comb. Frequency combs are useful for spectroscopy
because they provide access to a wide range of colors that can be used
to distinguish various substances.



==========================================================================
To create a dual-comb spectroscopy system with extremely fast acquisition
and a wide range of colors, the researchers brought together techniques
from several different disciplines, including nanofabrication, microwave electronics, spectroscopy and microscopy.

The frequency combs in the new system use an optical modulator driven by
an electronic signal to carve a continuous laser beam into a sequence
of very short pulses. These pulses of light pass through nanophotonic
nonlinear waveguides on a microchip, which generates many colors of
light simultaneously.

This multi-color output, known as a supercontinuum, can then be used to
make precise spectroscopy measurements of solids, liquids and gases.

The chip-based nanophotonic nonlinear waveguides were a key component
in this new system. These channels confine light within structures that
are a centimeter long but only nanometers wide. Their small size and
low light losses combined with the properties of the material they are
made from allow them to convert light from one wavelength to another
very efficiently to create the supercontinuum.

"The frequency comb source itself is also unique compared to most other
dual- comb systems because it is generated by carving a continuous laser
beam into pulses with an electro-optic modulator," said Carlson. "This
means the reliability and tunability of the laser can be exceptionally
high across a wide range of operating conditions, an important feature
when looking at future applications outside of a laboratory environment." Analyzing gases and solids To demonstrate the versatility of the new
dual-comb spectrometer, the researchers used it to perform linear
absorption spectroscopy on gases of different pressure. They also
operated it in a slightly different configuration to perform the
advanced analytical technique known as nonlinear Raman spectroscopy
on semiconductor materials. Nonlinear Raman spectroscopy, which uses
pulses of light to characterize the vibrations of molecules in a sample,
has not previously been performed using an electro-optic frequency comb.



==========================================================================
The high data acquisition speeds that are possible with electro-optic
combs operating at gigahertz pulse rates are ideal for making spectroscopy measurements of fast and non-repeatable events.

"It may be possible to analyze and capture the chemical signatures
during an explosion or combustion event," said Carlson. "Similarly, in biological imaging the ability to create images in real time of living
tissues without requiring chemical labeling would be immensely valuable to biological researchers." The researchers are now working to improve the system's performance to make it practical for applications like real-time biological imaging and to simplify and shrink the experimental setup so
that it could be operated outside of the lab.


========================================================================== Story Source: Materials provided by The_Optical_Society. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. David R. Carlson, Daniel D. Hickstein, Scott B. Papp. Broadband,
electro-
optic, dual-comb spectrometer for linear and nonlinear measurements.

Optics Express, 2020; 28 (20): 29148 DOI: 10.1364/OE.400433 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200916131037.htm

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