ABSTRACT
Spatial light modulators enabling complex light field manipulation has opened up many opportunities in biomedical imaging, holographic display, and adaptive optics. However, traditional spatial light modulators do not allow multi-color operations simultaneously due to their physical constraints, while multi-color modulations are highly desirable in many applications. To overcome this limitation, we demonstrate a multi-color spatial complex light field modulation with a single binary hologram on digital micromirror devices (DMD). This method combines several neighboring micro-mirror pixels into a giant single superpixel, in which the light field's amplitude and phase can be individually determined by internal pixel combinations, and the dynamic range of phase modulation can exceed 2π for the single wavelength. As a result, this extra phase modulation range offers an additional degree of freedom for independent multi-wavelength light modulation. Based on this scheme, multi-color light modulations have been demonstrated in a 2D plane as well as in multiple 3D holographic planes. Moreover, a dual-colored Airy beam has been realized using the same technique. These results bring complex light modulation into a multi-color regime, paving the way for practical applications in information display, imaging, and optical trapping.
ABSTRACT
Levitation by optical tweezers provides a unique non-invasive tool for investigating a microscale object without external perturbations. Here we experimentally levitate a micrometer-sized water droplet in the air using an optical tweezer. Meanwhile, vibrational modes of a levitated water droplet are excited by modulating the trapping laser. From their backscattered light, vibrational modes with mode numbers are observed in the spectra. Additionally, their corresponding free spectral ranges are analyzed and compared with theory and numerical simulations. This Letter, establishing a non-invasive and all-optical detection technique of optomechanical properties of levitated droplets, paves the way for their practical applications in aerosol and biomedical science.
ABSTRACT
Vitamin D and its metabolites have been recognized as key determinants in innate immune modulation. In this study, we investigated the regulation of antibacterial functions of oral keratinocyte cells by 25-hydroxyvitamin D3 (25VD3). OKF6/TERT2 cells, an immortalized human oral keratinocyte cell line, were transfected with or without 24-hydroxylase small interfering RNA (siRNA) and incubated with different amounts of 25VD3. These epithelial cells expressed high levels of inactivating 24-hydroxylase (CYP24A1) and relatively low levels of activating 1α-hydroxylase (CYP27B1) in the presence of 25VD3. 25VD3 influenced the expression of vitamin D-driven genes and cathelicidin in a dose-related manner. SiRNA specific to 24-hydroxylase augmented the cathelicidin production and subseqently influenced the antibacterial activity on multispecies of oral pathogens. These observations suggest that 25VD3 is capable of stimulating cathelicidin production and modulating antibacterial function upon CYP24A1 knochdown in oral epithelial cells, and indicate novel mechanisms that 25VD3 may enhance antibacterial ability in oral keratinocytes.
