Talbot effect in waveforms containing subwavelength multilobe superoscillations.

The self-imaging of periodic light patterns, also known as the Talbot effect, is usually limited to periods that are larger than the wavelength. Here we present, theoretically and experimentally, a method to overcome this limitation by using superoscillating light patterns. The input intensity distribution is a periodic band-limited function with relatively large periods, but it contains regions of multilobe periodic oscillations with periods that are smaller than half of the wavelength. We observe the revival of the input pattern, including the subwavelength superoscillating regions, at large distances of more than 40 times the optical wavelength. Moreover, at fractional Talbot distances, we observe even faster local oscillations, with periods of approximately one-third of the optical wavelength.

Multi-lobe superoscillation and its application to structured illumination microscopy.

Superoscillating function is a band-limited function that is locally oscillating faster than its highest Fourier component. In this work, we study and implement methods to generate multi-lobe optical superoscillating beams, with nearly constant intensity and constant local frequency. We generated superoscillating patterns having up to 12 sub-wavelength oscillations, with local frequency of 20% to 40% above the band-limit. We then test the potential application of these beams to super-resolution structured illumination microscopy. By utilizing the Moiré effect on a fluorescent grating, we have demonstrated experimentally resolution improvement over the conventional sinusoidal illumination. Our simulations show that structured illumination microscopy with super oscillating multi-lobe beams can provide more than twofold improvement in resolution, with respect to the classical diffraction limit and for coherent or incoherent modalities.

Directional release of the stored ultrashort light pulses from a tunable Bragg-grating microcavity.

We demonstrate numerically the ability for directionally releasing the stored ultrashort light pulse from a microcavity by means of two-pulse nonlinear interaction in a cascading Bragg grating structure. The setting is built by a chirped grating segment which is linked through a uniform segment, including a tunable microcavity located at the junction between the two components. Our simulations show that stable trapping of an ultrashort light pulse can be achieved in the setting. The stored light pulse in a microcavity can be possibly released, by nonlinearly interacting with the lateral incident control pulse. Importantly, by breaking the symmetry of potential cavity, the stably trapped light pulse can be successfully released from the microcavity to the expected direction. Owing to the induced optical nonlinearity, the released ultrashort light pulses could preserve their shapes, propagating in a form of Bragg grating solitons through the uniform component, which is in contrast to the extensively studied light pulse trappings in photonic crystal cavities which operate at the linear regime.

Slow-light all-optical soliton diode based on tailored Bragg-grating structure.

All-optical soliton diode (AOSD) is proposed based on a sandwich nonlinear Bragg-grating structure: a linearly chirped Bragg-grating linked to a uniform Bragg-grating and again to a chirped Bragg-grating. The nonreciprocity is achieved by introducing two spatially asymmetric chirped Bragg-gratings with optical nonlinearity. High transmission ratio up to 150 is obtained when launching a picosecond Gaussian pulse into the setting. We find that such pulses in a form of solitons propagate at a rather small velocity (<0.03c) when pulse wavelength is selected in the vicinity of photonic bandgap.