We have experimentally investigated the effects of sidewall corrugations on the beam quality and brightness ofnarrow-ridge interband cascade lasers (ICLs) emitting at λ ≈ 3.3 μm. We find that at this wavelength a corrugationperiod of 10 μm provides greater suppression of higher-order lateral modes than a shorter period of 2-4 μm. Whilethe power and efficiency decrease modestly for the longer corrugation period, there is a net increase of thebrightness defined as the output power divided by the beam quality factor M~2. However, the brightness degradeswhen the corrugation amplitude is increased from 2 μm to 3.5 μm, since lower output power offsets a relativelysmall improvement of the beam quality.
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