Fourier transform infrared spectroscopy with visible light

Area of Science:

• Quantum Optics
• Spectroscopy
• Materials Science

Background:

• Mid-infrared (MIR) spectroscopy traditionally requires cooled detectors, limiting accessibility and increasing costs.
• Nonlinear interferometers offer an alternative by detecting correlated visible light, enabling the use of non-cooled, high-performance detectors.
• Spontaneous parametric down-conversion (SPDC) is a key nonlinear optical process for generating correlated photon pairs.

Purpose of the Study:

• To develop a new approach for spectral information registration in the mid-infrared range.
• To combine a nonlinear interferometer with Fourier-transform spectroscopy for enhanced spectral analysis.
• To achieve broad spectral coverage and high resolution without spectrally selective detection.

Main Methods:

• Utilized a nonlinear interferometer employing non-degenerate spontaneous parametric down-conversion (SPDC).
• Employed broadband non-collinear SPDC in periodically poled lithium niobate (PPLN) to increase spectral coverage.
• Integrated the nonlinear interferometer with a Fourier-transform spectroscopy concept for data acquisition.

Main Results:

• Achieved continuous spectra with a spectral bandwidth exceeding 100 cm^-1.
• Demonstrated transmission spectra of a polypropylene sample in the 3.2–3.9 µm range.
• Obtained spectral resolution of 6 cm^-1 without the need for spectrally selective detectors.

Conclusions:

• The developed nonlinear interferometer combined with SPDC and FTS provides an effective method for MIR spectroscopy.
• This approach offers broad spectral coverage and high resolution using readily available non-cooled detectors.
• The technique shows promise for efficient material characterization in the mid-infrared spectrum.