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

TL;DR

This paper demonstrates that sub-wavelength metallic aperture patterning on the facet of mid-infrared laser diodes can selectively enhance a single lateral mode, resulting in a cleaner, single-peak emission spectrum.

Contribution

The study introduces a novel facet patterning technique that controls lateral mode reflectivity, enabling single-mode operation in mid-infrared laser diodes.

Findings

Spectrum shifts from multiple peaks to a single peak after patterning

Simulations confirm differential reflectivity for lateral modes

Facet patterning effectively suppresses unwanted modes

Abstract

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.