High-resolution oxygen absorption spectrum obtained with an external-cavity continuously tunable diode laser

Area of Science:

• Atomic and Molecular Spectroscopy
• Laser Physics
• Atmospheric Chemistry

Background:

• The oxygen (O(2)) A band electronic transition is crucial for atmospheric remote sensing and understanding photochemistry.
• Traditional spectroscopic methods using monolithic diode lasers are limited by mode-hop issues, restricting continuous spectral scans.
• External-cavity diode lasers (ECDLs) offer potential for improved tunability but require validation for specific spectroscopic applications.

Purpose of the Study:

• To measure the electronic absorption spectrum of the oxygen A band (b(1)Sigma(+)(g) <0xE2><0x86><0x90> X(3)Sigma(-)(g)) near 760 nm in ambient air.
• To demonstrate the utility of a newly available external-cavity diode laser for high-resolution spectroscopy.
• To assess the advantages of ECDLs over standard Fabry-Perot lasers for accessing specific absorption transitions.

Main Methods:

• Utilized a newly available external-cavity diode laser for spectral measurements.
• Employed 2f modulation spectroscopy for high-sensitivity detection.
• Performed continuous, single-mode scans of the P branch of the oxygen A band spectrum.
• Conducted measurements in room air at approximately 760 nm.

Main Results:

• Successfully measured the electronic absorption spectrum of the oxygen A band (b(1)Sigma(+)(g)(nu'=0) <0xE2><0x86><0x90> X(3)Sigma(-)(g)(nu''=0)) near 760 nm.
• Demonstrated that the external-cavity diode laser enables continuous, single-mode scanning without mode hops.
• Verified the capability of ECDLs to access absorption transitions within their gain bandwidth (635 to 1550 nm).

Conclusions:

• The external-cavity diode laser is a powerful tool for measuring atmospheric oxygen spectra with high precision.
• ECDLs overcome the limitations of traditional diode lasers, enabling broader applications in spectroscopy.
• This technology facilitates the study of absorption transitions previously inaccessible due to mode-hop issues.