We report on the observation of optically induced transparency (OIT) in a compact microresonator in an ambient environment by introducing a four-wave mixing gain to nonlinearly couple two separated resonances of the micro-cavity. Its optical-controlling capacity and non-reciprocity characteristics at the transparency windows are also demonstrated. Active-controlling of the OIT can be achieved by varying a strong pump beam, while a small frequency-detuning of the pump can lead to a Fano-like asymmetric resonance justifying the interference nature of OIT. Furthermore, OIT observed here is a non-reciprocal one, since FWM gain is a unidirectional one owing to the conservation law of momentum.
A perfect lens with unlimited resolution has always posed a challenge to both theoretical and experimental physicists.
Recent developments in optical meta-materials promise an attractive approach towards perfect lenses using negative
refraction to overcome the diffraction limit, improving resolution. However, those artificially engineered meta-materials
usually company by high losses from metals and are extremely difficult to fabricate. An alternative proposal on using
negative refraction by four-wave mixing has attracted much interests recently, though most of existing experiments still
require metals and none of them has been implemented for an optical lens. Here we experimentally demonstrate a metalfree
flat lens for the first time using negative refraction by degenerate four-wave mixing with a simple thin glass slide.
We realize optical lensing utilizing a nonlinear refraction law, which may have potential applications in infrared
microscopy and super-resolution imaging.