Spectroscopic Measurements – New High-Speed Method

Researchers have discovered a new method for faster spectroscopic measurements. They observed changes in the light spectrum by using simple, rapid polarization measurements by linking polarization to the color of a pulsed laser. The technique opens up new possibilities for measuring spectral changes over the complete color spectrum of light in a nanosecond time frame.

Spectroscopic measurements with the new technology consist of a change in the wavelength of probe light (color) after interaction with a sample. Examining these changes offers an opportunity to study the properties of materials at the atomic scale.

The researchers performed a modulation (using a birefringence crystal) in the temporal domain by coherently splitting a femtosecond pulse of a laser into two parts. Each part had a different polarization, slightly delayed in time relative to the other. The new technique can find applications in material science research involving fundamental analysis of atoms and molecules and astronomical observations.

Researchers demonstrated a simple method for producing spectral vector beams (i.e., light with a strong correlation between its polarization and wavelength components). Using this direct correlation, they demonstrate that high-speed spectroscopy (for example, tracking a narrow line absorption or transmission) can be accomplished using only polarization measurements. Because such measurements can be made with fast photodetectors, the method can track changes in the frequency spectrum at readout rates limited only by the laser’s repetition rate and the detectors’ response time (i.e., in the GHz regime).

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