Dynamically encircling an exceptional point (EP) of a non-Hermitian system, in which the parameters are continuously varied around the EP, offers direction dependent conversion into orthogonal eigenstates that is robust to input state variation. The requirement for adiabatic conditions in the encircling, equating to very slow modulation in parameter space about the EP, ultimately results in long path lengths. This proves a strong limitation on the use of passive materials for mode conversion in such systems, as including loss becomes necessary. Thus, in passive converters, output of the converted mode will have very small intensity and be difficult to integrate into larger systems. Here we experimentally demonstrate chiral conversion into orthogonal supermodes by dynamic encirclement of an EP in an active, nonlinear system of two coupled waveguides. The introduction of gain allows for sufficiently adiabatic systems with control of output intensity, equaling or amplifying that of the input signal. This work paves the way for further use of active media in chiral mode converters, as well as the fabrication of semiconductor lasers with direction dependent mode output, more suitable for integration into larger systems.
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