Cavity enhanced absorption spectroscopy using a broadband prism cavity and a supercontinuum source.

Area of Science:

• Spectroscopy
• Molecular Physics
• Optical Engineering

Background:

• Cavity enhanced spectroscopy offers high sensitivity for detecting weak molecular transitions.
• Previous methods faced limitations in broadband applicability and reflectivity.

Purpose of the Study:

• To design and construct a cavity enhanced absorption spectrometer.
• To demonstrate its capability in measuring weak molecular absorption spectra.

Main Methods:

• Utilized broadband Brewster's angle prism retroreflectors.
• Employed a spatially coherent supercontinuum excitation source (500 nm to >1.75 µm).
• Achieved high effective cavity reflectivity (>99.99% at 1.064 µm) using fused silica prisms.

Main Results:

• Successfully recorded cavity enhanced absorption spectra of molecular oxygen (O2) and acetylene (C2H2).
• Achieved noise equivalent absorption (αmin) of 7.21x10⁻⁸ cm⁻¹ Hz⁻¹/² for O2 and 1.28x10⁻⁷ cm⁻¹ Hz⁻¹/² for C2H2.
• Observed narrow line widths of 0.18 cm⁻¹ for O2 and 0.44 cm⁻¹ for C2H2.

Conclusions:

• The developed spectrometer is effective for high-sensitivity absorption spectroscopy.
• Demonstrated proof of principle for weak transition measurements.
• The design enables sensitive detection of molecular species.