Unidirectional acoustic transmission in asymmetric bull's eye structure

Unidirectional acoustic transmission has been investigated in an asymmetric bull's eye structure, which consistes of a subwavelength hole with concentric grooves on one side of a thin steel plate. When acoustic waves impinge normally on the groove side of the asymmetric structure, a strong acoustic transmitted energy flux is observed in the frequency range of 400–450 k Hz, while there is no obvious transmitted energy flux in the same frequency range if the acoustic waves impinge normally on the other side. Thus, a remarkable unidirectional acoustic transmission behavior is exhibited by the current structure. With changing the period of the grooves, it is found that the transmitted acoustic energy flux keeps unchanged while the frequency of the transmitted waves can be modified. The experiments are performed, which has confirmed the unidirectional acoustic transmission behavior in the asymmetric bull's eye structure. The asymmetric bull's eye structure may have potential application in ultrasound diagnosis and therapy.

The structures of eye and surrounding tissues of Longman's beaked whale,Indopacetus pacificus

Observations were made on one eye from a Longman’s beaked whale Indopacetus pacificus, which was probably one of the least known extant cetaceans. The whale died shortly after swimming aground on the coast in the Nishikata Beach, Sendai-shi, Kagoshima-ken Prefecture, Japan, on July 26, 2002. It was a mature female with body length 6.45 m. This paper documented the basic structural characteristics of her visual organ of the whale in order to better understand this animal.

Compound diffractive telescope system:design,stray light analysis,and optical test

The compound diffractive telescope is a novel space optical system which combines the structure of compound eyes with diffractive optics and so it has a lighter weight, a wider field of view （FOV）, a lower cost as well as looser fabrication tolerance. In this paper, the design of a compound diffractive telescope composed of one primary lens and twenty-one eyepieces is introduced. Then the influence of diffraction orders on the performance of the system is analysed. A modified phase function model of diffractive optics is proposed to analyse the modulation transfer function （MTF） curves for 0° FOV, which provides a more accurate prediction of the performance of the system. In addition, an optimized mechanism is also proposed to suppress stray light. The star image and resolution tests show that the system can achieve diffraction limit imaging within ±2° of FOV and 4-4 mm of eccentricity. Finally, a series of pictures of an object are taken from different channels, and the splicing of pictures from adjacent FOVs is demonstrated. In summary, the designed system has been proved to have great potential applications.

Integrated colloidal quantum dot photodetectors with color-tunable plasmonic nanofocusing lenses

High-sensitivity photodetection is at the heart of many optoelectronic applications,including spectroscopy,imaging,surveillance,remote sensing and medical diagnostics.Achieving the highest possible sensitivity for a given photodetector technology requires the development of ultra-small-footprint detectors,as the noise sources scale with the area of the detector.This must be accomplished while sacrificing neither the optically active area of the detector nor its responsivity.Currently,such designs are based on diffraction-limited approaches using optical lenses.Here,we employ a plasmonic flat-lens bull’s eye structure(BES)to concentrate and focus light into a nanoscale colloidal quantum dot(CQD)photodetector.The plasmonic lenses function as nanofocusing resonant structures that simultaneously offer color selectivity and enhanced sensitivity.Herein,we demonstrate the first CQD photodetector with a nanoscale footprint,the optically active area of which is determined by the BES;this detector represents an exciting opportunity for high-sensitivity sensing.