Single Lateral Mode Mid-Infrared Laser Diode using Sub-Wavelength Modulation of the Facet Reflectivity

The characteristics of mid-infrared laser diodes have been investigated before and after the patterning of sub-wavelength metallic apertures on the emitting facet. Before modification of the facet the emitted spectrum consisted of a large number of peaks associated with different spatial modes, whereas afterwards the spectrum was dominated by a single peak. Simulations showed that the patterning of the facet caused the effective reflectivity to be different for each lateral mode, suggesting that the peak in the measured spectra is associated with the single lateral mode which is most strongly reflected from the modified facet.