Cryoless MIR spectroscopy via pump wavelength scanning using PPLN ridge waveguide upconversion.

Area of Science:

• Optics and Photonics
• Spectroscopy
• Non-linear Optics

Background:

• Traditional Fourier Transform Infrared (FTIR) spectroscopy for mid-wave infrared (MWIR) detection is often limited by high costs and the need for cryogenic cooling.
• Developing compact and practical spectroscopic tools for the MWIR range remains a significant challenge in analytical chemistry and materials science.

Purpose of the Study:

• To present a novel room-temperature mid-wave infrared (MWIR) spectroscopy technique.
• To overcome the limitations of existing FTIR methods by developing a cryogen-free, miniaturized spectroscopic approach.

Main Methods:

• Utilized a 2 cm-long periodically poled lithium niobate (PPLN) ridge waveguide for optical upconversion.
• Employed a low-power, continuous wave monochromatic pump laser, sweeping its wavelength to sample MWIR spectra.
• Detected the upconverted signal using sensitive silicon detectors.

Main Results:

• Successfully demonstrated a "non-linear spectrometer" capable of sampling MWIR spectra at room temperature.
• Experimental validation using a channelled spectrum showed accurate recovery of thermal source spectral modulation.
• Achieved a low relative error of 3% in spectral modulation recovery.

Conclusions:

• The developed upconversion-based MWIR spectroscopy technique is a robust and promising alternative to conventional methods.
• This approach paves the way for the development of miniaturized, practical, and cost-effective MIR spectroscopic instruments.
• The room-temperature operation and use of silicon detectors enhance the practicality and accessibility of MWIR spectroscopy.