Qingsong Bai

A Practical Model of Quartz Crystal Microbalance in Actual Applications

A practical model of quartz crystal microbalance (QCM) is presented, which considers both the Gaussian distribution characteristic of mass sensitivity and the influence of electrodes on the mass sensitivity. The equivalent mass sensitivity of 5 MHz and 10 MHz AT-cut QCMs with different sized electrodes were calculated according to this practical model. The equivalent mass sensitivity of this practical model is different from the Sauerbrey’s mass sensitivity, and the error between them increases sharply as the electrode radius decreases. A series of experiments which plate rigid gold film onto QCMs were carried out and the experimental results proved this practical model is more valid and correct rather than the classical Sauerbrey equation. The practical model based on the equivalent mass sensitivity is convenient and accurate in actual measurements.

Measuring microwave cavity response using atomic Rabi resonances

In this letter, an atom-based approach for measuring the microwave (MW) cavity response (including cavity frequency and Q-factor) is presented, which utilizes a MW magnetic field detection technique based on atomic Rabi resonances. We first identify the Rabi resonances on seven π transitions in Cs atoms and demonstrate their uses in continuously frequency-tunable field detectors. With the atom-based field detectors, we then indicate the possibility of reconstructing the MW cavity response by measuring the MW frequency-dependent Rabi frequency (i.e., MW field strength) inside the cavity. To demonstrate this approach, we measured the response curves of a 9.2-GHz cavity and a cavity resonating at 8.3 GHz and 9.7 GHz using π transitions and σ transitions, respectively. We compared the results measured by our approach with those measured by Vector Networker Analyzer and obtained good agreement. From such atom-based, SI-traceable measurements, the MW cavity response can be linked directly to the Rabi frequency,...

The Resistance–Amplitude–Frequency Effect of In–Liquid Quartz Crystal Microbalance

Due to the influence of liquid load, the equivalent resistance of in-liquid quartz crystal microbalance (QCM) increases sharply, and the quality factor and resonant frequency decreases. We found that the change in the resonant frequency of in-liquid QCM consisted of two parts: besides the frequency changes due to the mass and viscous load (which could be equivalent to motional inductance), the second part of frequency change was caused by the increase of motional resistance. The theoretical calculation and simulation proved that the increases of QCM motional resistance may indeed cause the decreases of resonant frequency, and revealed that the existence of static capacitance was the root cause of this frequency change. The second part of frequency change (due to the increases of motional resistance) was difficult to measure accurately, and may cause great error for in-liquid QCM applications. A technical method to reduce the interference caused by this effect is presented. The study contributes to the accurate determination of the frequency and amplitude change of in-liquid QCM caused by liquid load, which is significant for the QCM applications in the liquid phase.

Simulation of the Ramsey cavity response

Ceramic Sealing Window (CSW) and Frequency Tuning Rod (FTR) are two important components of the Ramsey cavity. Here, a complete electromagnetic model of the Ramsey cavity is built with Finite-element tool HFSS, and the effects of CSW and FTR on the cavity response are simulated and analyzed in detail. To achieve high coupling efficiency, the estimated parameter ranges of CSW and FTR are investigated. The results obtained here offer a helpful guide for Ramsey cavity design in Cs and Rb beam clocks.

Attosecond synchronization of passive mode-locked lasers using optical heterodyne techniques

We demonstrate an attosecond synchronization of mode-locked lasers using optical heterodyne technique. The measured RMS timing fluctuation between two mode-locked Er:fiber lasers with same color was about 800 attosecond within 60 s.

Dual-mode Ramsey cavity for a dual Rb/Cs atomic clock

In this paper, we propose a dual-mode Ramsey cavity for a dual Rb/Cs atomic clock, with resonances at 6.83GHz and 9.19GHz under the two different operating modes, respectively. Thus, the proposed cavity can excite Rb atoms and Cs atoms clock transition in the same environment (e.g., static magnetic field, temperature, and/or the asymmetric length between the two arms due to a single U-shaped structure). This design provides a compact physical package for a dual Rb/Cs clock. Another potential application of the dual-mode is high-accuracy comparison measurement. As an example, a dual-mode cavity with TE105 and TE109 modes was simulated.

Using QCM for field measurement of liquid viscosities in a novel mass-sensitivity-base method

In this paper, a novel mass-sensitivity-based method for field measurement of liquid viscosities using a quartz crystal microbalance (QCM) is presented. And a model which yields a quantitative description of the influence of the liquid properties on the oscillation frequency is established as well. The viscosity of liquids (which loaded on a QCMs center) could be quickly and conveniently obtained using this model by measuring the frequency shift of QCM and the radius of liquid drop. Two groups of verified experiments are performed using two different QCMs, and the experimental data show that the presented method is efficient.

A novel voltage controlled temperature compensated crystal oscillator for eliminating the trim effect

A novel scheme of voltage controlled temperature compensated crystal oscillator (VCTCXO) which could realize frequency adjustment and temperature compensation simultaneously is presented. The scheme is based on the binary function V = F(T, ft) which could be obtained from the temperature experiments, where ft is the target output frequency (controlled and adjusted by external control voltage); T is the ambient temperature and V is the compensating voltage. Through extending the two-dimensional temperature-frequency characteristics curve to three-dimensional surface and using a microcontroller to works out compensating voltages according to the above binary function, this new approach provides the possibility for eliminating the adverse influence of trim effect on traditional temperature compensated crystal oscillators (TCXOs).