Optical dephasing of a near infrared dye in PMMA: photon echoes using the superconducting accelerator pumped free electron laser

Abstract A superconducting accelerator pumped free electron laser is used to perform picosecond photon echo experiments on the near infrared dye 1,1′,3,3,3′,3′-hexamethylindotricarbocyanine iodide (HITCI) in poly(methyl methacrylate) (PMMA). The temperature dependence of the optical dephasing is measured from 1.5 to 10 K. At the lowest temperatures a temperature dependence, T −1.4 , characteristic of two-level system glass dynamics is observed. Above 5 K, the optical dephasing is exponentially activated with an activation energy of 15 cm −1 . This is the same activation energy reported for rhodamine B in PMMA, demonstrating that 15 cm −1 corresponds to an intrinsic glass mode. These are the first photon echo experiments, and to our knowledge, the first nonlinear optical coherence experiments, performed using a FEL as a source.

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