Linjie Zhang

High sensitivity spectroscopy of cesium Rydberg atoms using electromagnetically induced transparency

A high sensitivity spectroscopy of Rydberg atoms is presented by using electromagnetically induced transparency (EIT) in the 6S(1/2)-6P(3/2)-n D ladder-type system of cesium vapor cell at room temperature. The EIT spectra of 40 D Rydberg state are measured and the dependences of the EIT magnitude and linewidth on the coupling laser power are investigated in detail. The Rydberg EIT linewidth is measured to be about 5.6 MHz when the powers of probe and coupling lasers are 50 microW and 5.2 mW, respectively, and which is close to the natural linewidth of cesium atoms. The effect of double resonance optical pumping on EIT is also investigated. The fine structures of nD (n = 39-55) are measured and the experimental result is in agreement with quantum defect theory.

Lifetime measurement of ultracold caesium Rydberg states

We measure the nS and nD (n = 30–40) state lifetimes of caesium Rydberg atoms in a conventional magneto-optical trap using the field ionization technique, which is consistent with the existing theoretical model through suppressing collisions and super-radiance effects. We also investigate variation of the lifetimes with densities of Rydberg atoms by changing the pulse energy of the dye laser. The results indicate that collisions and super-radiance effects have a large influence on the accuracy of lifetime measurement at high densities of Rydberg atoms.

Evolution of the pairs of ultracold Rydberg atoms in the repulsive potential

We present the explicit dynamics process of Rydberg cesium atoms initially experiencing a repulsive van der Waals (vdW) interaction by measuring the line width and intensity of the Rydberg ionization spectra. The signals of Rydberg atoms and free ions are recorded simultaneously within an initial 3.5 micros delay time between the excitation laser and the ramp electric field. For high-density gases, a rapid decrease of Rydberg atoms and an increase of free ions are observed, which is not found to be the case for low-density gases. The experimental results indicate that superradiance is the main cause of the redistribution of Rydberg atoms from the repulsive potential to the attractive potential for high density, which provides the initial ionization. The corresponding theoretical calculation is also given.

Near-IR telecommunication diode laser based double-pass QEPAS sensor for atmospheric CO2 detection

A novel double pass quartz enhanced photoacoustic spectroscopy (QEPAS) sensor for atmospheric CO2 detection is developed by use of a 1.5 μm telecommunication diode laser. A low-cost high-reflection concave mirror is positioned behind a traditional QEPAS based acoustic detection module to enhance the absorption optical path and improve the detection sensitivity. The obtained minimum detection limit is 29 ppmV for 1 s averaging time which corresponds to a normalized noise equivalent absorption coefficient (NNEA, 1σ) of . With a 247 s averaging time, it demonstrates an ultimate detectable sensitivity of 1.74 ppmV.

Direct measurement of laser-induced frequency shift rate of ultracold cesium molecules by analyzing losses of trapped atoms

We report on a quantitative experimental determination of the laser-induced frequency shift rate of the ultracold cesium molecules formed via photoassociation (PA) by means of the trap loss measurement of the losses of trapped atoms in a standard magneto-optical trap. The experiment was directly performed by varying the photoassociation laser intensity without any additional frequency monitor technologies. Our experimental method utilized dependences of the losses on the laser-induced frequency shift rate based on the conditions of the identified photoassociation spectral shape. We demonstrated that the method is sensitive enough to determine small frequency shifts of rovibrational levels of ultracold cesium molecules.

Dipolar Rydberg-atom gas prepared by adiabatic passage through an avoided crossing

The passage of cold cesium 49S

Measurement of Polarizability of Cesium nD State in Magneto-Optical Trap

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Collisional cross-sections measurement of ultracold caesium Rydberg states

Rydberg atoms through an electric-field-induced multi-level avoided crossing with nearby hydrogen-like Rydberg levels is employed to prepare a cold, dipolar Rydberg atom gas. When the electric field is ramped through the avoided crossing on time scales on the order of 100~ns or slower, the 49S

Splitting of an Electromagnetically Induced Transparency Window of a Cascade System with 133 Cs Rydberg Atoms in a Static Magnetic Field

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Quantum-Based Determination of Antenna Finite Range Gain by Using Rydberg Atoms

population adiabatically transitions into high-\emph{l} Rydberg Stark states. The adiabatic state transformation results in a cold gas of Rydberg atoms with large electric dipole moments. After a waiting time of about