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During the last years, organometallic lead halide perovskites (LHP) have been widely studied as outstanding materials for photovoltaics and photonics applications [1] . These emerging semiconductors are fabricated by cheap and straightforward solution process techniques on polycrystalline film of the compound CH 3 NH 3 PbX 3 (X=Cl, Br, I). Their outstanding properties of these films include large absorption coefficients above the bandgap, high electronic mobilities, high quantum yield of emission at room temperature or tunable band-gap with the composition [1] . In this work, we exploit the excellent light emitting and photodetection properties of CH 3 NH 3 PbI 3 thin films to integrate a waveguide amplifier and a photodetector within the same LHP thin film deposited in both rigid (SiO 2 /Si) and flexible (nanocellulose) substrates. As illustrated in Figure 1a , the device is based on the refractive index contrast between the LHP, a poly(methyl methacrylate) capping layer the substrate to engineer the number of propagating modes and their propagation constant [1] . In particular, the geometrical parameters of the structure were carefully designed to propagate an excitation beam injected at the input edge of the structure together with the photoluminescence (PL) emitted by the LHP through a mode that is extremely confined in the semiconductor film (see Fig. 1a ). As a result, this bilayer structure demonstrates amplified the spontaneous emission (ASE) with extraordinary low thresholds (2 nJ) [2] . Moreover, the incorporation of electrodes on the top of the LHP allows us to study a photocurrent dependent on the excitation light ( Fig. 1b ), and with it to monitor electrically the generation of PL and ASE ( Fig. 1c ). Experimental results (symbols in Fig. 3c) are properly reproduced with the simulations carried out with a rate equation model (solid lines in Fig. 3c). Here, we carefully compare the generation of optical gain and photocurrent in rigid and flexible substrates and demonstrate that the choice flexible substrate does not significantly alter the performances of the device [3] . Therefore, this approach illustrates a new amplifier-photodetector device that can pave the road towards a flexible and wearable technology LHP based technology. |
