High-power diode laser spectrally narrowed with prism-etalon feedback

Area of Science:

• Optics and Photonics
• Laser Physics

Background:

• Diode lasers often exhibit broad linewidths, limiting their use in high-resolution applications.
• Achieving narrow linewidths typically requires complex or less flexible methods.

Purpose of the Study:

• To present a simple and flexible method for reducing the linewidth of diode lasers.
• To maintain high output power during linewidth reduction.

Main Methods:

• Utilized a dispersive prism and a thin etalon for retroreflective feedback.
• The etalon generated periodic spectral selectivity through weak external cavities.
• Investigated spectral properties with varying etalon thicknesses and operating currents.

Main Results:

• Reduced linewidth of a blue diode laser by 20-fold, from several nanometers to 70 pm (3.6 cm-1).
• Achieved an output power of 3 W at 2.15 A with the narrowed linewidth.
• Demonstrated scalability to 4 W output power with a 100 pm (5.1 cm-1) linewidth at 2.75 A.

Conclusions:

• The prism-etalon feedback method effectively narrows diode laser linewidth while preserving high output power.
• This technique offers significant flexibility, applicable across visible and near-infrared spectra, unlike fixed gratings.