Photonic integration on membranes can be used to combine electronic and optical functionality. An InP membrane on Si (IMOS)  is an advantageous solution, since it can include lasers, detectors and waveguide devices. In order to scale down the footprint of active devices such as photonic crystal nanolasers (Fig. 1a.), active passive regrowth is necessary. This paper reports on the design of the active layer stack and development of an active-passive regrowth process for integrated active devices which are butt-coupled to membrane waveguides. A first realized structure with this technique is shown in Fig. 1b.