# Exclusive Effect in Rydberg Atom-Based Multi-Band Microwave Communication

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## Abstract

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## 1. Introduction

## 2. Experiment Setup

## 3. Theory

## 4. Result and Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) Experimental schematic setup of the three infrared laser driven Rb Rydberg-based MW receiver and (

**b**) relevant energy levels diagram. All infrared lights are generated by external cavity semiconductor lasers and frequency-stabilized by PDH system with the ultra stable Fabry–Perot cavity. The Rb atoms in vapor cell are excited successively to the $41{\mathrm{F}}_{7/2}$ Rydberg state by $780\mathrm{nm}$, $776\mathrm{nm}$, $1260\mathrm{nm}$ lasers, which is also coupled with MW1 on the transition $41{\mathrm{F}}_{7/2}\leftrightarrow 41{\mathrm{G}}_{9/2}$ and MW2 on neighboring transition $41{\mathrm{F}}_{7/2}\leftrightarrow 42{\mathrm{D}}_{5/2}$, as shown in underlying figure. The terminology in the upper figure about optical components: $\lambda /2$-WP is acronym of a half-wave plate; PBS is polarization beam splitter; ID is iris diaphragms; PD is photodetector; DM is dichroic mirror and M is silver mirror.

**Figure 2.**The recorded photoelectric signal intensity of baseband signals by our Rydberg atom-based receiver for different E-intensities of MW1 and MW2. In either case, (

**a**) or (

**b**), the intensity of the baseband signal with ${\omega}_{1}=2\times 2\pi $ kHz (${\omega}_{2}=4\times 2\pi $ kHz) modulated onto MW1 (MW2) gradually decay with the intrusion of the opponent MW power beyond ${E}_{\mathrm{MW}}\sim 2.5\mathrm{mV}/\mathrm{cm}$. However, in both cases, the signal intensity climbs up along its own channel microwave intensity until reaching the maximum at ${E}_{\mathrm{MW}}\sim 13\mathrm{mV}/\mathrm{cm}$, and then drops again, implying an available power optimization.

**Figure 3.**The power spectrum of fast Fourier transform of the photoelectric signal accepted by the Rydberg atom-based receiver in the condition of various pairs of MW E-intensities. (

**a**) The increasing of the MW1 power enhances the signal amplitude of its own channel, until ${E}_{\mathrm{MW}1}\sim 11\mathrm{mV}/\mathrm{cm}$, but weakens its opponent always gradually. (

**b**) Similar to (

**a**), but the turning point occurs at ${E}_{\mathrm{MW}2}\sim 10\mathrm{mV}/\mathrm{cm}$.

**Figure 4.**(

**a**) Experimental and (

**b**) theoretical result of the situation that the power of two channels are changed simultaneously. The gradual pink surface represents the variation of ${\omega}_{1}=2\times 2\pi $ kHz frequency component, and the gradual dark blue surface signifies the ${\omega}_{2}=4\times 2\pi $ kHz frequency component. The magenta line is the intersection of two surfaces, which means the intensity of two frequency component are equal when the work point is set on this line. Whether from the experimental observation or the theoretical simulation, we can see that the influence of one channel on the optical gain reduction of the other channel is very obvious, and the theoretical and experimental results are consistent in the trend.

**Figure 5.**The spectral AT splitting for small change of the microwave field at target signal channel (

**a**) and auxiliary channel (

**b**). The auxiliary field helps to make the AT splitting gets more obvious for better quantization of the weak target field, but it reduces the sensitivity of the dynamic microwave-optical amplifying gain, which is much smaller than that of the auxiliary field itself.

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**MDPI and ACS Style**

You, S.; Cai, M.; Zhang, H.; Xu, Z.; Liu, H. Exclusive Effect in Rydberg Atom-Based Multi-Band Microwave Communication. *Photonics* **2023**, *10*, 328.
https://doi.org/10.3390/photonics10030328

**AMA Style**

You S, Cai M, Zhang H, Xu Z, Liu H. Exclusive Effect in Rydberg Atom-Based Multi-Band Microwave Communication. *Photonics*. 2023; 10(3):328.
https://doi.org/10.3390/photonics10030328

**Chicago/Turabian Style**

You, Shuhang, Minghao Cai, Haoan Zhang, Zishan Xu, and Hongping Liu. 2023. "Exclusive Effect in Rydberg Atom-Based Multi-Band Microwave Communication" *Photonics* 10, no. 3: 328.
https://doi.org/10.3390/photonics10030328