Ultrafast Optical Control of Polariton Energy in an Organic Semiconductor Microcavity

Abstract

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.

Embrace the darkness: An experimental perspective on organic exciton–polaritons

“…113 Similar spectral contributions can arise from thermal excitations within the mirror, 78,105 miniscule thermal expansion of the cavity active layer, 78 overlapping photoinduced absorption from the intracavity dark states, 92,106 or transient changes to the background refractive index. 78 Indeed, the polariton spectral shifts induced by photoexcitation of uncoupled molecules have recently been exploited to induce ultrafast control of the LP emission energy, 114 demonstrating that these FIG. 4.…”

“…III) 78 and exploited to control the polariton energy in real time. 114 Similarly, ultrafast energy migration in densely packed films of organic materials usually causes rapid depolarization following excitation; approaching the condensation threshold, stimulated relaxation can short-circuit such depolarization, resulting in an increase in the density of transitions aligned with the exciting laser. This effect serves to magnify the reduction in Rabi splitting.…”