We experimentally report on the evolution from singly-dressed to doubly-dressed four-wave mixing （FWM） process by controlling the powers of the probe, the pump and the dressing fields respectively. The differences in the enhancement and the suppression of FWM signal between the two-level and cascade three-level atomic systems are observed and explained by the multi-dressed effect theoretically. Both the x direction and the y direction spatial splittings of the degenerate-FWM （DWFM） beams are obtained. We also investigate the switch between the enhancement and the suppression of the DWFM signals and between its spatial splittings in x direction and y direction. The spatial splittings in x direction and y direction can be controlled by the relative position and the intensity of the involved laser beams. Such a study can be useful for optimizing the efficiency of the FWM process and providing potential applications in spatial signal processing.
We simultaneously compare the probe transmission,Four-Wave Mixing(FWM)and fluorescence signals with dressing effects in a four-level atomic system.The variation rules of three types of signals are exhibited by changing the frequency detuning and power of incident laser beams.The interplay between two ladder subsystems is investigated in the Y-type atomic system.In particular,the fluorescence signal with ultra-narrow linewidth is obtained due to being sheared twice by the electromagnetically induced transparency window.Such fluorescence with very high coherence and monochromaticity can be used for the quantum correlation and narrow linewidth laser.
A method of multi-beam femtosecond laser irradiation combined with modified HF-HNO3-CH3COOH etching is used for the parallel fabrication of all-silicon piano-concave microlens arrays （MLAs）. The laser beam is split by a diffractive optical element and focused by a lens to drill microholes parallely on silicon. An HF-HNO3-H2SO4-CH3COOH solution is used to expand and polish laser-ablated microholes to form micro- lenses. Compared with the HF-HNO3-CH3COOH solution, the solution with H2SO4 can effectively reduce the etched surface roughness. The morphologies of MLAs at different laser powers and pulse numbers are observed. The image array formed by the silicon microlenses is also demonstrated.
A method for fabricating deep grating structures on a silicon carbide （SIC） surface by a femtosecond laser and chemical-selective etching is developed. Periodic lines corresponding to laser-induced structure change （LISC） are formed by femtosecond laser irradiation, and then the SiC material in the LISC zone is removed by a mixed solution of hydrofluoric acid and nitric acid to form grating grooves. Grating grooves with a high-aspect ratio of approximately 25 are obtained. To obtain a small grating period, femtosecond laser exposure through a phase mask was used to fabricate grating structures with a 1.07 μm period on the surface of the SiC.
We report the multi-component optical azimuthons of four-wave mixing （FWM） composed of several modulated vortex beams, the so-called azimuthons, in V-type three-level and two-level atomic systems. We analyze the formation mechanisms of the FWM azimuthons theoretically and experimentally. In addition, we illustrate the interactions between the co-propagating azimuthon components. Finally, we also compare the stabilities of azimuthons in V-type three-level and two-level atomic systems.
