Electromagnetically induced transparency-like effect in the degenerate triple-resonant optical parametric amplifier.

We investigate experimentally the absorptive and dispersive properties of the triple-resonant optical parametric amplifier (OPA) for the degenerate subharmonic field. In the experiment the subharmonic field is utilized as the probe field and the harmonic wave as the pump field. We demonstrate that the electromagnetically induced transparency (EIT)-like effect can be simulated in the triple-resonant OPA when the cavity linewidth for the harmonic wave is narrower than that for the subharmonic field. However, this phenomenon cannot be observed in a double-resonant OPA. The narrow transparency window appears in the reflected field. Especially in the measured dispersive spectra of the triple-resonant OPA, a very steep variation of the dispersive profile of the subharmonic field is observed, which can result in a slow light as that observed in an atomic EIT medium.