High power 7-GHz bandwidth external-cavity diode laser array and its use in optically pumping singlet delta oxygen.

Area of Science:

• Optics and Photonics
• Laser Physics
• Physical Chemistry

Background:

• Diode laser arrays are crucial for various applications but often suffer from broad spectral bandwidths.
• Narrowing laser bandwidth is essential for high-resolution spectroscopy and selective molecular excitation.
• Efficient generation of singlet delta oxygen ((1)Delta) molecules has applications in areas like chemical lasers and photochemistry.

Purpose of the Study:

• To narrow the spectral bandwidth of a continuous-wave (cw) operated diode laser array.
• To achieve efficient generation of singlet delta oxygen ((1)Delta) molecules using the narrowed laser output.
• To demonstrate the capability of temperature tuning the laser frequency across a specific oxygen absorption line.

Main Methods:

• Utilized a 14-mm thick volume Bragg grating to narrow the spectral bandwidth of a cw diode laser array.
• Characterized the output power and spectral bandwidth (Full Width at Half Maximum - FWHM) of the modified laser.
• Employed temperature tuning of the laser frequency to align with the O(2) X(3)Pi --> b(1)Sigma(+) absorption line at 763.8 nm.

Main Results:

• Successfully narrowed the spectral bandwidth of the diode laser array to 7 GHz (FWHM).
• Achieved a total cw output power of 13.5 W, with 86% concentrated within the 7-GHz bandwidth.
• Demonstrated temperature tuning of the laser frequency to precisely match the target oxygen absorption line.

Conclusions:

• A 14-mm thick volume Bragg grating effectively narrows the spectral bandwidth of a cw diode laser array.
• The narrowed bandwidth and tunable frequency enable efficient generation of singlet delta oxygen ((1)Delta) molecules.
• This technique provides a viable method for selective excitation of molecular oxygen.