We study Rydberg atoms modulated by strong radio-frequency (RF) fields with a frequency of 70 MHz. The Rydberg atoms are prepared in a room temperature cesium cell, and their level structure is probed using electromagnetically induced transparency (EIT). As the RF field increases from the weak-into the strong-field regime, the range of observed RF-induced phenomena progresses from AC level shifts through increasingly pronounced and numerous RF-modulation sidebands to complex state-mixing and level-crossings with high-l hydrogen-like states. Weak anharmonic admixtures in the RF field generate clearly visible modifications in the Rydberg-EIT spectra. A Floquet analysis is employed to model the Rydberg spectra, and good agreement with the experimental observations is found. Our results show that all-optical spectroscopy of Rydberg atoms in vapor cells can serve as an antenna-free, atom-based and calibration-free technique to measure and map RF electric fields and to analyze their higher-harmonic contents.

We present a laser frequency locking to Rydberg transition with electromagnetically induced transparency (EIT) spectra in a room-temperature cesium vapor cell. Cesium levels 6S 1/2 , 6P 3/2 , and the nD 5/2 state, compose a cascade three-level system, where a coupling laser drives Rydberg transition, and probe laser detects the EIT signal. The error signal, obtained by demodulating the EIT signal, is used to lock the coupling laser frequency to Rydberg transition. The laser frequency fluctuation, ∼0.7 MHz, is obtained after locking on, with the minimum Allan variance to be 8.9 × 10 −11 . This kind of locking method can be used to stabilize the laser frequency to the excited transition.

The combinations of nano-ZnO with wood through simple and efficient physical methods to prepare environmentally friendly and versatile Nano-ZnO-coated Wood have important research and practical implications. In this paper, an environmentally friendly nano-ZnO-coated wood was prepared by physical magnetron sputtering using Pinus sylvestris L. var. mongholica Litv. The micro-characteristics, structure, wettability and colour change of the ZnO-coated wood were characterized and studied. For samples with a sputtering time of more than 3 min, the surface water contact angle exceeded 130° and had good hydrophobic properties. After a 168 h accelerated ultraviolet (UV) ageing test, the total colour difference (ΔE∗) of the sample with a sputtering time of 75 min (200 °C) was 77% lower than that of the original wood. When the substrate was at 200 °C, the ZnO films deposited on the surface of the wood were evenly and densely arranged, forming almost a continuous film. It could be seen that the deposition of a nano-ZnO film on the surface of wood could significantly improve its hydrophobic properties and anti-UV photochromic properties.

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