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A study of the effects of the injected current and the thermal resistance on the tunability of antimonide-based diode lasers is presented. The studied diode lasers, emitting at around 2.3 μm, are dedicated to gas detection in the atmosphere, based on tunable-diode-laser absorption spectroscopy (TDLAS). This very useful technique requires, from the lasers, an emitted tunable wavelength able to cross a gas absorption line to detect the absorbed light. Typically a tuning rate of a few GHz/mA is sufficient to perform gas detection at atmospheric pressure (Vicet et al., 2002). It is then important to know and understand the tuning properties of the devices to achieve gas detection. They are very sensitive to thermal effects which are involved in all tuning processes. The lasers studied are shown to be well adapted to gas detection, paradoxically because of their large thermal resistance Rth which increases Joule heating, and mainly affects their tunability.