Subdiffraction propagation of images using saturated absorption of optical transition

Diffractionless transmission of optical beams through a four-level atomic system affected by a plasmonic nanostructure

A nondiffracting propagation of an optical beam through a four-level double-V-type quantum system near a plasmonic nanostructure is investigated. We study the linear absorption and dispersion properties of the quantum system as it interacts with two laser fields. We discuss the effect of the control beam with a Laguerre-Gaussian (LG) profile on the focusing of the probe beam in the presence of a plasmonic nanostructure. An appropriately selected control beam excites one transition of the atomic system and generates a spatially varying refraction index modulation for a weak probe beam that couples to the other transition. We demonstrate that placing a plasmonic nanostructure at a nanometer distance from the atomic system and using a control field with the spatial structure leads to the diffraction-less propagation of the probe beam through the atomic system. Also, it is shown that the optical properties and probe beam focusing can be controlled by adjusting the distance of the plasmonic nanostructure from the atomic system. The proposed all-optical waveguide with high contrast and transmission can be used to implement applications such as image transfer through the medium and image processing.

Selection and cloning of periodic optical patterns with a cold Rydberg atomic gas

We show that periodic optical patterns formed in a cold Rydberg atomic gas via electromagnetically induced transparency (EIT) can be selected by using a weakly modulated control laser field. We also show that the (hexagonal, stripe, square, etc.) patterns prepared in one probe laser field can be cloned onto another one with high fidelity via a double EIT.

Optical image cloning based on electromagnetic induced absorption

We investigate, both theoretically and experimentally, optical image cloning via electromagnetic induced absorption (EIA). We demonstrate the transfer of small 2D real images imprinted onto a strong coupling beam to a weak probe beam in a Rb vapor cell. We show through EIA that the coupling beam's image is cloned beyond the usual diffraction, with a potential improvement in spatial resolution of the cloned image by a factor of three in comparison to that of the original coupling beam. Optical cloning through EIA is based on position selective nonlinear absorption, and it does not rely on spatial modulation of the refractive index.

Spatially modulated thermal light in atomic medium for enhanced ghost imaging

Recent years have seen vast progress in image modulation based on atomic media, with potential applications in both classical optical imaging and quantum imaging regions. However, there have been few investigations of how thermal light images interact with an electromagnetically induced transparent medium. In this letter, we experimentally demonstrate pseudo-thermal light modulation on coherent population trapping conditions in ⁸⁷Rb vapor. By introducing the Laguerre-Gaussian beam as the control beam and the encoded speckle as the probe beam, we obtained sharper speckle patterns after the atom cell compared with that in free space. The spatially modulated thermal light was then used to enhance the image resolution in ghost imaging of which the resolution was enhanced by factor 3, since the ghost image resolution is heavily reliant on the speckle’s transverse coherent length. Our results are promising for potential applications in high resolution ghost imaging and image metrology, image processing and biomedical imaging.

Resolution enhancement of ghost imaging in atom vapor

Ghost imaging is an imaging technique in which the image of an object is revealed only in the correlation measurement between two beams of light, whereas the individual measurements contain no imaging information. Normally, the resolution of the image, which even exceeds the Rayleigh limit, is shown to be related to the transverse coherent length (l_c) of the speckle pattern. In this Letter, we demonstrate experimentally that the speckle size can be compressed by a coherent population trapping (CPT) process in atom vapor, and the resolution of GI can be greatly enhanced by the CPT process. The technique we exploit is quite efficient and robust, and it may be useful in the field of quantum and classical two-photon imaging, all-optical image processing, and quantum communication.

Investigating the self-healing property of an optical Airy beam

We report the theoretical and experimental study of the self-healing property of an Airy beam related to its phase. We find that, even when the phase of an Airy beam is not preserved, the beam still exhibits the self-healing property but undergoes a severe diffraction. To decrease the diffraction effect, we utilize an electromagnetically induced transparency (EIT) image-cloning system based on position selective absorption effect to further demonstrate the self-healing phenomenon. Our experimental results show excellent agreement with the theoretical analysis.

Transfer and conversion of images based on EIT in atom vapor

Transfer and conversion of images between different wavelengths or polarization has significant applications in optical communication and quantum information processing. We demonstrated the transfer of images based on electromagnetically induced transparency (EIT) in a rubidium vapor cell. In experiments, a 2D image generated by a spatial light modulator is used as a coupling field, and a plane wave served as a signal field. We found that the image carried by coupling field could be transferred to that carried by signal field, and the spatial patterns of transferred image are much better than that of the initial image. It also could be much smaller than that determined by the diffraction limit of the optical system. We also studied the subdiffraction propagation for the transferred image. Our results may have applications in quantum interference lithography and coherent Raman spectroscopy.

Image cloning beyond diffraction based on coherent population trapping in a hot rubidium vapor

Following recent theoretical predictions, we report on an experimental realization of image cloning beyond usual diffraction, through the coherent population trapping (CPT) effect in a hot rubidium vapor. In our experiment, an alphabet letter image was transferred from a coupling field to a probe field, based on the CPT effect. Furthermore, we demonstrate that the cloned probe field carrying the image is transmitted without the usual diffraction. To our best knowledge, this is the first experimental report about image cloning beyond diffraction. We believe this mechanism, based on CPT, has definite and important applications in image metrology, image processing, and biomedical imaging.