Tunable polariton absorption of distributed feedback microcavities at room temperature

We have demonstrated well-separated tunable polariton absorption for a semiconductor-cavity composite system in transmission measurements at room temperature. A distributed feedback microcavity of the fourth order is fabricated by spin coating a self-organized inorganic/organic multiple quantum wells, $({\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{C}}_2{\mathrm{H}}_4{\mathrm{NH}}_3{)}_2{\mathrm{PbI}}_4$, on a corrugated quartz substrate with a period of about $0.7\hspace{0.5em}\mu \mathrm{m}$. By changing the grating period or the incident angle, the absorption dips exhibit anticrossing behavior. Owing to the large excitonic oscillator strength of the material, the polariton mode splitting is as large as $100\hspace{0.5em}\mathrm{meV}$ even at room temperature. At the normal incidence, an exciton and a light form a strongly coupled standing wave, which corresponds to a cavity polariton in Fabry-Perot semiconductor microcavities.