Dark State Magnetometer Based on Enhanced Acousto-Optics Modulator
Round 1
Reviewer 1 Report
The authors present a detailed technical paper were they describe a set-up based on an AOM for observation of dark state magnetometer.
Even though the explanation is quite long a few aspects are unclear and need to be commented.
In the methods and in particular in the frequency measurement and monitoring region, the authors present fig.1 with elements that are not explained. What is the function of the wavemeter in the set-up? Can the authors provide a measurement of the wavemeter to demonstrate their stabilization scheme?
The authors mention a locking mechanism of the ECDL that also uses an FP interferometers without any information on the parameters of such interferometer ( Finesse? type?)
Figure 3 is provided without any colorbar that indicates the kind of dynamics in play.
Also it is not clear what specific scanning amplitude the authors have used in their measurment
finally, it is not really clear what are the limiting factors for the linewidth measured in figure 5? What could be chamged to improve the situation? What are the main parameters that affect this parameters.
Also, from the inset of Figure 5 it is quite clear that there is a fluctuation on the peak intensity and probably on the linewidth observed. Can the auhtors provide a statistics on the peak linewidth in order to have an estimation of the noise level of the presented technique?
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript reports on the setup and results of a dark state magnetometer based on acousto-optics modulators (AOM). The novel setup is simpler and potentially more stable with respect to laser fluctuations than previous designs and could improve this kind of magnetometry if magnetic field sensitivity remains low. The manuscript is easy to follow and well documented, but I find the experimental results not sufficiently described in detail to derive the main results of the work. Therefore I suggest a revision of text and results.
Here are specific comments on the manuscript:
lines 9-10: the manuscript does not demonstrate this point because the experimental results shown in the manuscript do not consider what happens to the dark state magnetometry in absence of frequency or temperature stabilization of the laser
line 161: typo in V_a
Figure1: I find it counter-intuitive to put the label omega_pm before the AOMs because the frequency is still omega_0.
line 194: here 30MHz of frequency shift is quoted and should correspond to a 1V modulation, but it is actually 1.6V as reported later on in the text
Figure 3: How are fluctuations defined? Amplitude, peak to peak, rms? What is the intensity fluctuation scale and unit? It is not reported in the image nor in the text.
I find confusing to have a graph where one axis is not meaningful nor useful for explaining the main results. If the time axis has no meaning why not to plot Amplitude (or better frequency shift) vs fluctuations or mean fluctuations?
Paragraph from line 172: the manuscript reports the problem of beam steering that can be solved by coupling to optical fibers. No fiber is present in Fig. 1, is there or not?
If not, the double pass AOM is the perfect solution in the ideal case but in the real case it can still cause displacements if the retroreflections are not perfectly collinear and beams have different waist and divergence on the exit lens. Given that this is the main point of the manuscript, was an optimization performed to minimize the steering? Was a test done to demonstrate that there is no steering?
line 212: Figure 4 does not show the quoted 0.7MHz/G
Figure 5: what are the units of the gaussian (I suppose, no fitting is mentioned in the text) fit, placed at the bottom of the plot?
Where are the calibrations that are used for the final result of 168Hz? They are not reported. Without them, the results mentioned are not reproducible by the reader: If I take as calibration the quoted AOM frequency shift of 30MHz/1.6V, which is roughly the range shown in figure, and apply it to the 4ms ramp shown in figure, the width w of 0.25ms (I assume this is in ms since the x-axis is) corresponds to about 1MHz. Orders of magnitude are not consistent, this invalidates one of the claims of the manuscript.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
I thank the author for the clear answers, I still have few comments regarding the replies:
Point 6: the error bar added in figure does not help in understanding. The definition of fluctuations (rms, mean, what is the number quoted? What unit? Relative, absolute measure?) is still not written. One can only guess without a description
Point 8: I suggest to mention this in the manuscript
Point 10: this is clearly automatic fitting, but the question is different. If fit parameters are reported in a figure because these are needed for extracting a final result, one should explain which kind of fitting formula it is not make the reader guess.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
