Observation of an Electromagnetically Induced Grating in Cold 85Rb Atoms
Round 1
Reviewer 1 Report
The paper describes an interesting series of experiments on electromagnetically induced gratings in a Rb cold atoms ensemble.
A useful introduction is provided and clear figures are presented, illustrating the results.
The behaviour of the induced grating is studied as a function of various experimental parameters and compared to analogous behaviour in thermal atoms. Differences in behaviour are emphasized such as the change in EIG with the coupling laser intensity.
The experimental details are provided and the paper is clearly written overall.
I believe the paper should be of considerable interest to the relevant scientific communities.
Very minor amendments to the English would improve the presentation but is not essential as the meanings are clear..
Author Response
Response to Reviewer 1 Comments
The paper describes an interesting series of experiments on electromagnetically induced gratings in a Rb cold atoms ensemble. A useful introduction is provided and clear figures are presented, illustrating the results. The behavior of the induced grating is studied as a function of various experimental parameters and compared to analogous behavior in thermal atoms. Differences in behavior are emphasized such as the change in EIG with the coupling laser intensity. The experimental details are provided and the paper is clearly written overall. I believe the paper should be of considerable interest to the relevant scientific communities.
Response: We wish to thank the reviewer for his/her careful review, and for endorsing publication of our manuscript. We have followed the suggestion to improve the manuscript.
Point 1: Very minor amendments to the English would improve the presentation but is not essential as the meanings are clear.
Response 1: We carefully checked the text content of the manuscript and made some modifications.
Changes: The detailed changes are listed in the labeled manuscript.
Reviewer 2 Report
Authors present experimental results on generation of the optical grating using electromagnetically induced transparency with the standing wave as the control field. Authors use the V-type three level system describing EIT in cold 85Rb atoms. Authors observe a spatial intensity distribution of the (D2 transition) probe field with a diffraction pattern – the EIT grating. Two major control parameters in EIT scheme - the intensity of the control field (D1 transition) and the two-photon detuning – are used to manipulate the EIT scheme and the grating. In contrast to previous results showing spectral properties of EIT grading only, authors demonstrate a diffraction pattern of EIT grating in a visual form in real time.
Authors also perform numerical analysis of the dispersion and absorption of the probe field as a function of two control parameters. Authors observe a rapid phase change of the probe field when apply a hybrid control scheme with different one-photon detunings. Authors nicely described the amplitude and the hybrid grating arising from the magnitude of the one-photon detuning of the probe filed. It would be useful to understand the role of the crossbeam angle and the grating constant in the creation of the diffraction pattern. What are the limiting factors here? If to increase the grating constant, the higher control field could possibly still provide the distinguishable diffraction pattern.
Altogether, the paper is clearly written and has scientific merit. I may recommend it for publication in the present form with optional revisions.
Author Response
Response to Reviewer 2 Comments
Authors present experimental results on generation of the optical grating using electromagnetically induced transparency with the standing wave as the control field. Authors use the V-type three level system describing EIT in cold 85Rb atoms. Authors observe a spatial intensity distribution of the (D2 transition) probe field with a diffraction pattern – the EIT grating. Two major control parameters in EIT scheme – the intensity of the control field (D1 transition) and the two-photon detuning – are used to manipulate the EIT scheme and the grating. In contrast to previous results showing spectral properties of EIT grading only, authors demonstrate a diffraction pattern of EIT grating in a visual form in real time. Authors also perform numerical analysis of the dispersion and absorption of the probe field as a function of two control parameters. Authors observe a rapid phase change of the probe field when apply a hybrid control scheme with different one-photon detunings. Authors nicely described the amplitude and the hybrid grating arising from the magnitude of the one-photon detuning of the probe filed. Altogether, the paper is clearly written and has scientific merit. I may recommend it for publication in the present form with optional revisions.
Response: We thank the reviewer for endorsing the main focus and conclusion comment about our manuscript. We have followed the suggestions point by point to improve the manuscript.
Point 1: It would be useful to understand the role of the crossbeam angle and the grating constant in the creation of the diffraction pattern. What are the limiting factors here? If to increase the grating constant, the higher control field could possibly still provide the distinguishable diffraction pattern.
Response 1: We thank the reviewer for the valuable suggestion. The grating constant d is determined by the angle between the two coupling lasers, and the susceptibility of this system changes with the change of the grating constant, which can be seen from Eq. (1) in the manuscript. The different susceptibilities will result in different refractive indexes. With fine adjustment of the small angle between the two coupling lasers, we can obtain a clear diffraction pattern with a suitable refractive index. In fact, we have measured the diffraction patterns with changing the angle between the two coupling lasers from 0.08 to 0.20 degree. Through comparison, we get the main results as follows: Firstly, the grating constant decreases as the angle increases, causing the decrease of the distance between two adjacent patterns. Secondly, when the angle is too small, the diffraction phenomenon is hard to be detected by the probe beam. While when the angle is too large, the grating constant is smaller, so that the diffraction patterns become dense and less distinguishable. The similar research phenomena can be found in our group’s previous work [Front. Phys. 52603(14), 2019]. Therefore, if we increase the grating constant, with the higher control field the diffraction pattern can indeed be distinguished, but the observed diffraction orders is less. And in this case the diffraction pattern obtained from the experiment is not good enough to be used as the research object. Thirdly, a better diffraction pattern with enough diffraction orders and higher diffraction intensity can be obtained when the angle is near 0.13 degree. Therefore, we carried out the further detailed study with this angle.
Changes: We add the content below in the revised manuscript.
“The grating constant is determined by the angle of the two coupling lasers. When the angle is too small, the diffraction phenomenon is hard to be detected due to the less diffraction orders. While when the angle is too large, the diffraction patterns become dense and less distinguishable. The crossing angel θ of two coupling lasers is about 0.13 degree in this work, which resulted in a grating constant of 175 μm and a better diffraction pattern.”
