The manipulation of exciton–polaritons and their condensates is of great interest due to their applications in polariton simulators and high‐speed, all‐optical logic devices. Until now, methods of trapping and manipulating such condensates are not dynamically reconfigurable or resulted in an undesirable reduction in the exciton–photon coupling strength. Here, a new strategy for the ultrafast control of polariton resonances via transient modification of an optical cavity mode is presented. Multilayer organic semiconductor microcavities that contain two absorbers are constructed: one strongly‐coupled to the cavity photon mode and one that is out‐of‐resonance. By selectively exciting the out‐of‐resonance absorber using ultrashort laser pulses, the cavity refractive index is modulated, and fully‐reversible blueshifts of the lower polariton branch by up to 8 meV in sub‐ps timescales with no corresponding reduction in the exciton–photon coupling strength are generated. This work demonstrates the ability to manipulate polariton energy landscapes over ultrafast timescales with important applications in emerging computing technologies.

This study uses a laser patterning setup to write defect structures into a conjugated polymer microcavity. We show that the defect enhances optical confinement and reduces the lasing threshold.

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