Product Code: ICA12_M1001

Infrared-Visible Light Conversion Using DCM Dye Micrograins Embedded in a Resin Sheet and Application to an IR Sensor Card
Authors:
Tadashi Kawazoe, Electrical Engineering and Information Systems, The Univ. of Tokyo; Bunkyo-ku Japan
Tohru Fujita, Central Research Labs, Hamamatsu Photonics KK; Hamakita Japan
Hiroyasu Fujiwara, Central Research Labs, Hamamatsu Photonics KK; Hamakita Japan
Minoru Niigaki, Central Research Labs, Hamamatsu Photonics KK; Hamakita Japan
Motoichi Ohtsu, Electrical Engineering and Information Systems, The Univ. of Tokyo; Bunkyo-Ku, Tokyo Japan
Presented at ICALEO 2012

We report high-efficiency visible light emission (λ=600690 nm) from aggregated 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM) dye micrograins excited by infrared light (λex = 805 nm). The light-emitting regions were localized at the surfaces and edges of the micrograins, where the optical near-field was more intense. This has been theoretically explained by excitonphonon polaritons, i.e., the dressed photon model, in which an electron is excited due to a multistep transition via an intermediate phonon state coupled with a localized exciton polariton (a dressed photon). The lifetime (about 1 ps) of the intermediate state has been measured by the pumpprobe method. We prepared a resin sheet containing the DCM and identified the origin of the intermediate state as an O-H stretching vibration mode, by time-resolved Raman spectroscopy using a 10 fs pulsed laser as an excitation light source. As the molecules aggregated, the emission efficiency with visible light excitation (λ<550 nm) decreased, i.e., concentration quenching, whereas the emission efficiency with infrared excitation increased. This is because a broad O-H phonon band with strong oscillator strength is created by hydrogen bonds among the molecules, acting as an efficient intermediate phonon state for the multistep transition. An IR sensor card was also demonstrated.