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Fabrication and properties of chirped fibre gratings with reflection bandwidths exceeding 50 nm and narrow bandpass fibre grating filters

ground-state absorption cross-section ratio, are also considered in Fig. 2. It is shown that ESA leads to the presence of an optimal value of the absorbance for which the DFWM is maximized. Similar behavior has been also observed in the steady-state regime.4 Finally, DFWM experiment in a 2mm-thick Cr4’:GSGG crystal has been performed using an Nd:YAG laser operating at ho = 1.06 pm with 20-11s pulse duration. The forward and backward pump beams had equal energy, whereas the probe beam was sufficiently weak to be considered as a small-signal probe. A conjugate reflectivity of 0.6% has been achieved, in good agreement with the prediction of the transient four-level system theory (Fig. 3). Imaging capabilities of the phase conjugate mirror will be also presented. To conclude, transition-metalion solid-state media which exhibit saturation of their absorption for Nd-lasers are promising nonlinear solid-state materials for applications to laser Q-switching, near-infrared dynamic holography, and laser beam control through wavemixing interactions.