The nature of excited-state absorption in polymethine and squarylium molecules
Abbreviated Journal Title
IEEE J. Sel. Top. Quantum Electron.
excited state absorption; femtosecond; nonlinear optics; nonlinear; spectroscopy; polymethine dyes; quantum chemical calculations; white-light continuum; SYMMETRICAL CARBOCYANINES; ELECTRONIC-PROPERTIES; Engineering, Electrical & Electronic; Optics; Physics, Applied
Subpicosecond transient absorption measurements were performed for several polymethine and squarylium dyes in ethanol solution and a polymeric host over the spectral range 400-1500 nm. A variety of nonlinear effects including saturable absorption, reverse saturable absorption, and gain were observed and analyzed. We observe strong excited-state absorption (ESA) in all dyes in the range 450-600 nm. We also report the first prediction and observation of additional ESA bands in the near-infrared range. The predictions were based on quantum chemical calculations and the ESA experiments were performed with femtosecond pump-continuum probe techniques. For polymethine dye 2-[2-[3-[(1,3-dihydro-3,3-dimethyl-1-phenyl-2H-indol-2-ylidene) ethylidene]-2-phenyl-1-cyclohexen-1-yl]ethenyl]-3,3-dimethyl-1-phenylindolium perchorate, an additional ESA band was detected near 1250 nm, and for squarylium dye 1,3-Bis-[(1,3-dihydro-1-butyl-3,3-dimetyl-2H-benzo[e]indol-2-ylidene)methyl]squaraine, two additional ESA bands were found around 870- and 1380-nm, respectively. To further study the nature of these transitions, the steady-state excitation anisotropy was also studied and compared with predictions. The relationship between ESA spectra of organic dyes and their molecular structure is discussed.
Ieee Journal of Selected Topics in Quantum Electronics
"The nature of excited-state absorption in polymethine and squarylium molecules" (2001). Faculty Bibliography 2000s. 8143.