Arbitrary function resonance tuner of the optical microcavity with sub-MHz resolution.

Tuning the resonance frequency of an optical whispering gallery mode microcavity is extremely important in its various applications. Here we report the design and implementation of a function resonance tuner of an optical microcavity with a resolution of about 650 kHz (7 pm at 1450 nm band). A piezoelectric nano-positioner is used to mechanically compress the microsphere in its axial direction. Furthermore, the resonance can be periodically tuned as an arbitrary function, such as the sine and sigmoid functions, with over 99% fitting accuracy. This Letter greatly expands the application of ultrahigh quality factor microresonators in a multi-mode coupling system or time-floquet system.

Characterization of microresonator-geometry-deformation for cavity optomechanics.

We have studied the effect of geometry deformation on the mechanical frequencies and quality factors for different modes in the Whispering Gallery Mode (WGM) microresonators, that is unavoidable in the practical fabrication. The subsidence of the sphere and a more general condition with fewer symmetries and complex deformation of eccentricity, subsidence, and offset are first modeled in this paper, which could tune the mechanical frequency in a much wider spectral range than the pillar-diameter-induced perturbation. we also show that the mechanical quality factors for the non-whispering-gallery mechanical mode could be increased in the order of 4 magnitudes at a specific subsidence, and form a mechanical bound state in the continuum (BIC) which is induced by the symmetry breaking and reveals new mechanisms to confine radiation. A much broader BIC window width with higher mechanical quality factor could be achieved, which is of great importance in both fundamental research and scientific applications.

Synthesis and effects of new caffeic acid derivatives on nitric oxide production in lipopolysaccharide-induced RAW 264.7 macrophages.

In this study, 20 new derivatives of caffeic acid esters were synthesized and their inhibitory activities against the lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW264.7 macrophages were determined. Compounds 3l, 3r, 3s and 3t were found to decrease nitrite levels in a dose-dependent manner in LPS-induced cells and showed potent inhibitory activities against the NO production in RAW264.7 macrophages with IC50 values of 7.4, 5.9, 3.3 and 2.2 µM, respectively. They could be selected as compromising compounds for the later pharmacological study.