Influence of grating parameters on the performance of an ECDL emitting in the blue spectral region

The influence of the grating type (holographic or ruled), resolution, and polarization on the performance of an External Cavity Diode Laser (ECDL) emitting in the blue spectral region are investigated. The single mode ECDL is designed in Littrow configuration and uses an uncoated low-power GaN Fabry-Perot (FP) laser diode, which forms the gain medium. The emitted Fabry-Perot laser diode beam, which is TE-polarized in the plane of the p-n junction, after collimation, is directed incident on the grating. The frequency-selective element, which is used for longitudinal mode selection, is placed outside the FP laser diode cavity to form the extended cavity laser diode. The first-order diffraction is reflected directly into the FP laser diode, while the zero-order is the output from the ECDL. The slope efficiency, output power, power stability, tuning range, and linewidth of the blue ECDL are investigated using different gratings with different resolutions and orientations. The type and geometrical configuration of the dispersive element and its location relative to the antireflection-coated output facet of the FP laser diode are very important parameters in the performance.