Far-Field Patterns of Plasmon Waveguide Interband Cascade Lasers

The far-field patterns of InAs-based plasmon-waveguide interband cascade lasers are experimentally and theoretically investigated. It is shown that different ridge waveguide structures and metal contact configurations lead to distinctive far-field patterns. With the commonly adopted center metal contact on the top of the ridge waveguide, an undesirable double-lobe far-field pattern along the lateral direction is exhibited, while with two metal contacts near the edges of the ridge or a broad-area metal contact on the mesa structure, the more desirable single lobe far-field pattern is observed. These characteristic far-field patterns and their implications are discussed with the aid of a theoretical model which is in good agreement with our experimental results.