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.
The whispering gallery mode (WGM) lasing in a polydimethylsiloxane (PDMS)-based microresonator is demonstrated with a convenient and crafty approach. Fabricated by directly brushing dye-doped PDMS solution on an optical fiber, the microresonator is self-formed due to the high surface tension. The size of the resonator can be widely tuned by using different droplet volumes and brushing speeds across the optical fiber. Lasing with a threshold as low as 2.5 μJ/mm2 is observed in this kind of fiber-stand PDMS microresonator. We also investigate the dependence of the lasing threshold on the different polarizations of the pump laser and size of the microresonator. This kind of WGM microresonator will find applications in optical sensors and on-chip integrated systems.
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.
Recently, a concept of time reversed lasing or coherent perfect absorber (CPA) has been proposed by A. D. Stone and co-workers, and was shortly experimentally demonstrated by them. The CPA system is illuminated coherently and monochromatically by the time reverse of the output of a lasing mode and the incident radiation is perfectly absorbed. Shortly afterwards, Stefano Longhi extended the idea to realize a CPA for colored incident light, and have theoretically shown that the time reversal of optical parametric oscillation (OPO) in a nonlinear medium could also realize a colored CPA for incident signal and idler fields which can be seemed as a kind of nonlinear CPA. Here we present the realization of such time-reversed processes in nonlinear optics regime, including time-reversed second harmonic generation (SHG) for coherent absorption at harmonic frequency of the pump and time-reversed optical parametric amplification (OPA) for coherent attenuation of colored travelling optical fields. Time reversed SHG is carried out at both phase matching and mismatching conditions, which shows parametric near perfect absorption at the harmonic frequency of the pump. The time reversal of OPA is demonstrated experimentally in a nonlinear medium to form a coherent absorber for perpendicularly polarized signal and idler travelling waves, realizing in the condition of OPA by a type II phase matching scheme. The absorption of signal/idler pair occurs at some specific phase difference. This is the first experimental demonstration of coherent absorption processes in nonlinear optics regime.