Thiophene Dendrimers as Entangled Photon Sensor Materials

The ability to do spectroscopy with a small number of entangled photons is an important development in the area of materials and sensing. This report investigates the effects of increasing thiophene dendrimer generation on the cross-section for both entangled (sigma(E)) and random (delta(E)) two-photon absorption cross-sections. Nonlinear optical properties of dendrimers are an interesting area of study because of potential applications in optical signal processing and remote sensing, and the use of a nonlinear optical material as a sensor for entangled photons offers great possibilities for applications in quantum lithography. Entangled two-photon absorption (ETPA) experiments and two-photon excited fluorescence (TPEF) experiments vary by at least 10 orders of magnitude in the photon flux used to probe the material. ETPA cross-sections from liquid samples as well as those of thin-film samples are investigated. An increase in sigma(E) and delta(R) with increasing dendrimer generation is observed, suggesting that the thiophene groups within the dendrimer nonlinearly absorb in a cooperative manner, which is further evidenced in the variation of cross-section per thiophene group. The nonlinear spectroscopic features obtained by the TPEF measurements were also obtained by the ETPA experiments, despite the fact that 10 orders of magnitude fewer photons are used in the latter technique. All dendrimer generations investigated in this work are found to have great potential for applications in quantum optical devices.