Spatially modulated thermal light in atomic medium for enhanced ghost imaging

Mingtao Cao,Fuli Li,Hong Gao,Jinwen Wang,Xin Yang,Shuwei Qiu

doi:10.1038/s41598-017-08374-3

Abstract

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.

Highlights

Optical diffraction sets a fundamental limitation of the resolution in image formation for conventional optical devices and microscopy
There have been few studies showing how the thermal light image interacts with electromagnetically induced transparent (EIT) medium, and it is of importance and interest to consider how thermal light interacts with an EIT medium and whether the intensity correlation and coherent area of the speckles can be improved during the coherent population trapping (CPT) process
We demonstrate that the ghost image resolution can be enhanced by using different spatial control beam in the EIT medium

Summary

Introduction

Optical diffraction sets a fundamental limitation of the resolution in image formation for conventional optical devices and microscopy. It has been proven that the image profile of a speckle pattern can be compressed in the CPT process[15], which leads to much better resolution in ghost imaging (GI) experiments. We found that the nature of the thermal light was well maintained, and the compressed speckles from the atom cell improved ghost imaging resolution 1.4 times better than that in free space, and the image contrast was about 0.65. By coding different Laguerre-Gaussian (LG) charges onto the control beam, applying them to the atom vapor, we found that the speckles profiles became 1.2 times smaller comparing with that of in free space. The compressed speckle made ghost imaging resolution 3 times better

Methods

Results

Conclusion