[en] The cavity field spectrum of a cascade three-level atom interacting with single-mode field with Kerr-like medium in the cavity is investigated. The numerical results for the initial field in pure number state, coherent state and squeezed vacuum state are calculated, respectively. It is found that the Kerr-like medium affects the spectral structure even though the initial field is in vacuum when the atom is in upper level. In the case of strong input field, the number state spectrum shows two peaks with different heights; and the superposition state spectrum shows a multi-peak structure with an equal distance of two neighboring peaks. The spectral 'central frequency' shifts away from the resonant frequency with the increasing of average photon number.

[en] This paper presents a novel current sensor by using a resonant piezoresistive microcantilever combined with magnetic actuation for the first time. An actuation power of several microwatts was necessary for stable self-oscillation. The sensor measured the DC current by obtaining the electrothermally induced resonant frequency shift of the microcantilever as a result of the Joule heating dissipated when the DC current flowed through the Wheatstone bridge on the microcantilever. Two theoretical models were established between the microcantilever's resonant frequency and the square of the DC current. The experimental results showed that the accuracy in the range of 0.5–5 mA (apart from 0.5 mA) using the two models was 2.60% and 1.00% with correlation coefficient value R > 0.999 in both cases, respectively. The current sensitivity of the sensor was about −3.983 Hz mA⁻² in the range of 0.5–5 mA. To maintain stable results, the sensor chip should be sealed in vacuum and integrated into an oven-control system. (paper)

[en] The issues of surface stress-induced deflection of a microcantilever with various widths and overall microcantilever sensitivity enhancement of microcantilever-based biosensors are investigated in this paper. A remarkably precise and simple analytical formula for calculating surface stress-induced deflection of a microcantilever with various widths is deduced. Particularly, the effect of surface stress on the location of the microcantilever's neutral axis is considered. This explicit analytical formula is validated by the finite element method simulation. An analytical equation for computing the fundamental resonant frequency of a microcantilever with various widths is also derived. This paper explores the deflections and resonant frequencies of the microcantilevers having basic and modified shapes. It is found that minimizing the effective mass near the microcantilever's free end and the clamping width at the fixed end significantly enhances the overall microcantilever sensitivity. A novel microcantilever, which is expected to have much more excellent performance and overall sensitivity than the simple rectangular-shaped microcantilever, is proposed as sensor element in biological detection.

[en] This paper investigated the current sensitivity of a resonant sensor based on a magnetically actuated piezoresistive microcantilever in different resonant modes, which were the first flexural mode and the first and second torsional modes. The sensor was based on the idea of measuring the electrothermally induced resonance frequency shift as a result of the Joule heating dissipated when the DC current flowed through the Wheatstone bridge on the microcantilever. Two theoretical models between the microcantilever’s resonance frequency and the square of the applied DC current for the sensor operating under the flexural and torsional modes were established. From the experimental results, it can be seen that the current sensitivity of the first torsional mode is an order of magnitude greater than the first flexural mode, but less than that of the second torsional mode. In addition, the effect of the DC current’s direction on the measured results should be taken into account before detecting the DC current. (paper)