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

The article focuses on a method to significantly reduce the spectral linewidth of a multimode diode laser while maintaining high output power, using a combination of a dispersive prism and a thin etalon for retroreflective feedback. This approach was demonstrated on a blue laser diode, achieving a 20-fold linewidth reduction to about 70 pm (3.6 cm⁻¹) at 3 W output power, with flexibility across visible and near-infrared wavelengths. The method leverages the etalon's free spectral range to create weak external cavities for spectral selectivity, and the prism's dispersion to refine the feedback, offering advantages over traditional volume Bragg grating feedback in terms of tunability and power handling. Optimization parameters such as etalon thickness, diode current, and cavity length were explored, highlighting the technique's potential for applications requiring high-power, spectrally narrowed laser sources, such as portable Raman gas analyzers.