Master Oscillator Power Amplifiers (MOPAs) are laser devices suitable for applications requiring high brightness light sources (i.e. several Watts of output power and good beam quality). MOPAs are promising candidates for high speed direct modulation, as required for applications such as LIDAR, free space optical communications and laser projection displays. MOPAs usually comprise two sections: an index guided single lateral mode waveguide section acting as a Master Oscillator (MO) and a gain-guided tapered Power Amplifier (PA) section. Ideally, the single lateral and longitudinal mode generated by the MO is injected into the PA section where it undergoes free diffraction and amplification keeping its initial beam quality. However, MOPAs often exhibit instabilities that have been attributed to a combination of thermal effects and the residual reflectance at the amplifier front facet. In this talk, I will show you experimental and theoretical results on the dynamics of commercial 2-section MOPAs showing instabilities involving large emission wavelength jumps. In order to avoid these instabilities, we are developing a bent MOPA that includes an additional section for modulation purposes. This 3-section MOPA is the core of the transmitter of a space-borne atmospheric CO2 sensing LIDAR being developed in the framework of the FP7-Space Project BRITESPACE.