The progress of nanotechnologies has triggered the emergence of many photonic artificial structures: photonic crystals, metamaterials, plasmonic resonators. Recently the intriguing class of PT-symmetric devices– referring to Parity-Time symmetry – has attracted much attention. Their distinctive feature is that the refractive index profile of the structures is complex-valued due to the gain and/or loss, which are spatially separated in the system. They have special properties such as one-sided reflection and exceptional points, i.e. remarkable singularities, in the evolution of propagation constants of the relevant modes. Apart from fundamental research motivations, the tremendous interest in these artificial systems is strongly driven by the practical functionalities that can be achieved by modulating the values of gain and loss in such structures. Several academic reports of PT-symmetric laser structures that incorporate a loss grating or a loss section have been shown to display new functions that are directly related to the specific arrangement of gain and losses, well beyond the basic compensation. So the concept is mature enough for attempting its practical use in real-world applications. The PARTISYMO project aims at erecting an ambitious bridge between the novel fundamental physics concept of PT-Symmetry, and a new generation of devices for integrated optics. We identified two key generic advantages to work with gain and losses rather than established electro-optical non-absorbing systems for telecom operation at 1550 nm: (i) one can combine active (source) and passive (switch-type) functions from the same epitaxial stacks without the need of an expensive epitaxial regrowth step. (ii) the one sided reflectivity while still belonging to reciprocal phenomena, suggests a different effect of external radiation onto a laser, and a potentially larger immunity of optical feedback on lasers, a well-known impairment of lasers that calls, to mitigate it, for the costly addition of garnet-type magneto-optical isolators. In our project, we team two academic labs, C2N and LCF, with the industrial partner III-V Lab, to target a proof-of-concept of InP-based integrated devices that demonstrate both above advantages. One cannot overemphasize the possible importance of the one-sided behavior (the one-sided reflectivity): it should very likely result in the higher immunity of laser linewidth and wavelength to optical feedback from the fiber or optical line, thus leading to the perspective of isolator-free laser diodes in high-performance optical networks, that do not need the usual expensive placement of a garnet-based isolating element to retain their narrow and precise linewidth and frequency and that would remain so under feedback up to -15 dB at least. Laser diodes for telecom are a 2-billion-euros yearly market. Specifically, the project proposes to fabricate two elementary guided-wave devices, – a highly-feedback immune laser diode and a PT-symmetry based switch using laterally coupled waveguides – and next to fabricate their combination on the same active wafer. The wafer itself would be mostly used in gain-and-loss regimes. It would be the first step in a novel architecture for active or passive elements. The proof-of-concept would be also an innovative transfer of a fundamental physics idea to a real-world device. It could be exploited in other domains where electro-optical tuning of the refractive index real part is not a satisfying solution, namely in plasmonics and with glass- or silica-based photonics (it is noteworthy that metals and glass are poor in terms of electro-optical performance). The PARTISYMO project has a duration of 3.5 years, taking into account the impact of the move of C2N lab (former LPN+IEF) to its new building at the heart of the Université Paris-Saclay main campus, scheduled in September 2018, very carefully.