We herein present a theoretical and experimental study on magnetic-field enhanced modulation transfer spectroscopy (MTS) for the 5S_1/2 (F = 1) → 5P_3/2 (F′ = 0, 1, and 2) transitions of ⁸⁷Rb atoms. The density matrix equations are solved numerically to obtain the MTS spectra and an excellent agreement is found between the experimental and calculated results. In particular, the enhancement of the MTS signal for the F = 1 → F′ = 0 transition in the presence of the magnetic field is directly verified based on the comparison of the results calculated by neglecting with those calculated including the Zeeman coherences in the F = 1 ground state. The unexpected behaviors of the F = 1 → F′ = 1 transition are also examined.

This paper describes the first observation of polarization-selective four-wave mixing signals in conventional coupling-probe spectroscopy, specifically, saturation absorption spectroscopy in ⁸⁵Rb atoms. The four-wave mixing signal is induced by two counter-propagating laser beams in a degenerate multi-level atomic system, involving the $$F_g=3 \rightarrow F_e =2,3$$F g = 3 → F e = 2 , 3 , and 4 transitions of the ⁸⁵Rb D2 line. Consequently, the four-wave mixing signals copropagating along the probe beam induce polarization rotation of a linearly polarized probe beam. To distinguish these four-wave mixing signals from the resulting probe beam, we detect the polarization components orthogonal to the polarization direction of the input probe beam, depending on the linear polarization angles between the probe and coupling beams. The experimental findings demonstrate excellent agreement with theoretical results.

Mechanical sensors provide core keys for high-end research in quantitative understanding of fundamental phenomena and practical applications such as the force or pressure sensor, accelerometer and gyroscope. In particular, in situ sensitive and reliable detection is essential for measurements of the mechanical vibration and displacement forces in inertial sensors or seismometers. However, enhancing sensitivity, reducing response time and equipping sensors with a measurement capability of bidirectional mechanical perturbations remains challenging. Here, we demonstrate the buckling cantilever-based non-linear dynamic mechanical sensor which addresses intrinsic limitations associated with high sensitivity, reliability and durability. The cantilever is attached on to a high-Q tuning fork and initially buckled by being pressed against a solid surface while a flexural stress is applied. Then, buckling instability occurs near the bifurcation region due to lateral movement, which allows high-sensitive detection of the lateral and perpendicular surface acoustic waves with bandwidth-limited temporal response of less than 1 ms.

We experimentally and theoretically investigated the optimal condition of polarization spectroscopy for frequency stabilization on various pump beam intensities and vapor cell temperatures for the D${}_2$ closed transition line of ${}^{87}$Rb atoms. We compared the experimental results, such as the amplitude, width, and slope, of the polarization spectroscopy signal with the theoretical results obtained from the numerical calculation of temporal density matrix equations. Based on the results, we found the optimal parameters, such as the pump beam intensity and vapor cell temperature, for polarization spectroscopy. The theoretically expected optimal parameters were, qualitatively, in good agreement with the experimental results.

We report the characterization of the forced damped harmonic oscillations of ¹³³Cs atoms in a magneto-optical trap, which was realized by modulating the intensity of the lasers counterpropagating along the anti-Helmholtz coil axis. Trap parameters such as trap frequency, damping coefficient, and magnitude of the driving force were determined from the resonant vibrational amplitude of the ¹³³Cs atomic cloud depending on the modulation frequency of the modulated laser intensity. The experimental results were compared with the theoretical ones based on the simple two-level and multi-level atom models, considering all possible transition lines used to trap the ¹³³Cs atom, and were found to be consistent with their theoretical counterparts. Furthermore, we theoretically examined the effect of the repumping laser on trap parameters.