## 2 Experimental Setup  
A schematic of an experimental setup and relevant Rydberg EIT-AT four-level ladder diagram are shown in Figure 1a,b. A weak probe beam, with \(1/e^{2}\) waist \(90\)\(\upmu\)m and wavelength \(\lambda_{p}=852\) nm, and a strong coupling laser, with \(1/e^{2}\) waist \(135\)\(\upmu\)m and wavelength \(\lambda_{c}=510\) nm, are overlapped and counter-propagated through a room-temperature cylindrical cesium vapor cell. Both length and diameter of the cell are 25 mm. Cesium ground state \(|6S_{1/2}F=4\rangle\), excited state \(|6P_{3/2}F^{\prime}=5\rangle\), and Rydberg state \(|66S_{1/2}\rangle\) consist of a three-level EIT system. The coupling laser couples the transition, \(|6P_{3/2}F^{\prime}=5\rangle\rightarrow|66S_{1/2}\rangle\). The probe laser is frequency-locked to the transition \(|6S_{1/2}F=4\rangle\rightarrow|6P_{3/2}F^{\prime}=5\rangle\) using a polarization spectrum method. The microwave electric field with a frequency \(\sim\)15.21 GHz is emitted from an antenna that is placed at a distance of 86 cm from the vapor cell, see Figure 1a. The microwave field couples the Rydberg transition \(|66S_{1/2}\rangle\rightarrow|65P_{1/2}\rangle\), yielding a Rydberg EIT-AT spectrum.  
Figure 1: (color online) (**a**) Sketch of an experimental setup. The coupling, \(\lambda_{c}=510\) nm, and probe, \(\lambda_{p}=852\) nm, lasers counter-propagate through a cesium room-temperature vapor cell along the \(y\)-axis. The horn antenna, placed 86 cm far from the cell (not scaled), emits the microwave electric field with the frequency \(\sim 15.21\) GHz coupling Rydberg transition, producing an EIT-AT spectrum. The polarization of the microwave field is set to parallel to the polarization of probe and coupling beams. The probe beam is passed through a dichroic mirror (DM) and is detected with a photodiode detector (PD). PBS: polarized beam splitter; (**b**) Energy level diagram of cesium cascade four-level system. The probe laser is resonant with the lower transition, \(|6S_{1/2}F=4\rangle\rightarrow|6P_{3/2}F^{\prime}=5\rangle\), and the coupling laser is scanned through the Rydberg transitions, \(|6P_{3/2}F^{\prime}=5\rangle\rightarrow|66S_{1/2}\rangle\). \(\Delta_{c}\) is the coupling laser detuning. The applied microwave electric field couples the transition, \(|66S_{1/2}\rangle\rightarrow|65P_{1/2}\rangle\), that forms Rydberg EIT-AT spectrum.  
The probe and coupling lasers have the same linear polarization along \(z\)-axis. The antenna is set such that the polarization of microwave field is paralleled to the laser-beam polarizations. This configuration leads to the two-peak EIT-AT spectral profile. The Rydberg EIT-AT signal is observed by measuring the transmission of the probe laser using a photodiode detector (PD) after a dichroic mirror (DM).  
The Rabi frequency of probe (coupling) laser is expressed as, \(\Omega_{p(c)}=\frac{\mu_{p(c)}}{\hbar}\sqrt{\frac{2P_{p(c)}}{\pi\omega_{p(c)} ^{2}\Omega_{0}}}\), with probe (coupling) laser power \(P_{p(c)}\), beam waist \(\omega_{p(c)}\), permittivity in vacuum \(\varepsilon_{0}\) and light speed \(c\). \(\mu_{p(c)}\) is the transition dipole moment corresponding to the probe (coupling) laser coupled transition, which can be calculated accurately [22]. We change the laser Rabi frequency by varying the laser power with a \(\lambda/2\) plate that is placed in front of a polarized beam splitter (PBS). Microwave field \(E_{MW}=\sqrt{30P_{MW}g}/d\)[23], with \(P_{MW}\) power of the microwave source, \(g\) gain of the antenna and \(d\) distance to the cell. The microwave field is in far-field regime, the distance \(d\) is set to 86-cm far from cell, which is larger than the far-field condition, \(d_{0}=65\) cm here.