We report what is to our knowledge the first experimental demonstration of a continuous coherent transient optical processor. A 13-bit pattern was stored as a spectral population grating in the Eu3+-ion ground state in a Eu3+:Y2SiO5 crystal. A 3120-bit data stream was processed continuously, yielding a cross-correlation signal that agreed well with theory. The data stream’s duration exceeded both the absorbing transition’s homogenous transverse dephasing time and upper-state lifetime. This experiment showed that by permanently storing the pattern as a population grating in the absorber’s ground state, coherent transient optical devices provide continuous, real-time data processing capability.
We experimentally investigate the transient dynamics of an optical cavity field interacting with large ion Coulomb crystals in a situation of electromagnetically induced transparency (EIT). EIT is achieved by injecting a probe field at the single photon level and a more intense control field with opposite circular polarization into the same mode of an optical cavity to couple Zeeman substates of a metastable level in 40Ca+ ions. The EIT interaction dynamics are investigated both in the frequency-domain – by measuring the probe field steady state reflectivity spectrum – and in the time-domain – by measuring the progressive buildup of transparency. The experimental results are observed to be in excellent agreement with theoretical predictions taking into account the inhomogeneity of the control field in the interaction volume, and confirm the high degree of control on light-matter interaction that can be achieved with ion Coulomb crystals in optical cavities.
Four-wave-mixing techniques were used to establish and probe population gratings of
Cr3+ ions in alexandrite crystals at temperatures between 10 and 300 K. The results were interpreted in terms of the interaction of the laser radiation with a two-level atomic system. They provide information about the characteristics of four-wave-mixing signals for this physical situation as well as being useful in characterizing the properties of energy transfer and dephasing within the ensemble of
Cr3+ ions. The patterns of the transient four-wave-mixing signals are consistent with a model based on the pumping dynamics of ions in the mirror and inversion crystal-field sites. The variation of the signal intensity with laser power is strongly affected by beam depletion. The characteristics of exciton migration among
Cr3+ ions in mirror sites were determined from the results of measuring the variation of the signal decay rate with grating spacing. The temperature dependences of the ion-ion interaction rate, the exciton-phonon scattering rate, and the diffusion coefficient were determined. These are found to be essentially the same for pumping into the
4T2 and
2E levels, but the effects of scattering from a grating of ions in inversion sites is much stronger for
4T2 pumping. The dephasing times for the atomic system were found from analyzing the variation of the signal intensity with grating spacing. For pumping into the
4T2 level the dephasing is dominated by radiationless decay processes. A model is presented for the decay channel that provides a theoretical explanation for the decay process which is consistent with the measured temperature and frequency dependences of the results as well as their variation with crystal-field strength. For pumping into the
2E level the dephasing is dominated by dephasing processes associated with the inhomogeneous linewidth of the transition.