We experimentally measure and theoretically model the light transmission characteristics of subwavelength apertures. The characterization consists of translating a point source at varying vertical height and lateral displacement from the aperture and measuring the resulting transmission. We define the variation of the transmission with lateral source displacement as the collection mode point sp...

As telescopes become larger, segmented and multi-aperture designs are being implemented to meet cost, size and weight constraints. These systems require alignment of the segments or sub-apertures to within fractions of a wavelength. We investigate the performance of phase diversity, a technique of image-based wavefront sensing, for characterizing and aligning segmented and multi-aperture system...

We examined the warming effects on the stomatal frequency, stomatal aperture size and shape, and their spatial distribution pattern of maize (Zea may L.) leaves using a light microscope, an electron scanning microscope, and geostatistic techniques. A field manipulative experiment was conducted to elevate canopy temperature by 2.08°C, on average. We found that experimental warming had little eff...

This work presents research results on a novel analytical model of electromagnetic system coupling through small size holes. The key problem regarding the coupling of two cavities through an aperture in separating screen of finite thickness without making assumption on smallness of any parameters is considered. We are the first to calculate on the base of rigorous electromagnetic approach the c...

In lasers with nonorthogonal eigenmodes the excess-noise factor K can be large, especially in unstable-cavity lasers with hard-edged intracavity apertures. To the best of our knowledge, we report the first detailed study of the dependence of K on aperture shape. Calculations and measurements of K for unstable-cavity lasers with variable-size apertures of triangular, square, pentagonal, hexagona...

We have measured the intensity profile and transmission of x rays focused by a series of biconcave spherical unit lenses fabricated from beryllium. The use of beryllium extends the range of operation of compound refractive lenses, improving transmission, aperture size, and gain. The compound refractive lens was composed of 160 biconcave unit lenses, each with a radius of curvature of 1.9 mm. Tw...

We show that three-dimensional incoherent primary sources can be reconstructed from finite-aperture Fresnel-zone mutual intensity measurements by means of coordinate and Fourier transformation. The spatial bandpass and impulse response for three-dimensional imaging that result from use of this approach are derived. The transverse and longitudinal resolutions are evaluated as functions of apertu...

We report on the development of a collection mode near-field probe for the terahertz spectral range. The near-field detector is based on an aperture type probe with dimensions of 30330 mm. The collection mode technique provides higher sensitivity and higher resolution than the similar illumination mode approach. Spatial resolution better than 40 mm is demonstrated for a broad spectrum of 300–60...

Conventional liquid microlens arrays are facing bottlenecks in controlling droplet size and shape, and limited aperture ratio. We report a new liquid/solvent approach to overcome these obstacles for making uniform droplet array and achieving approximately 90% aperture ratio. The droplets are very stable due to the pinning effect of the polymer walls and substrate surfaces. Using the fabricated ...

Nanoscale ridge aperture antennas have been shown to have high transmission efficiency and confined nanoscale radiation in the near field region compared with regularly-shaped apertures. The radiation enhancement is attributed to the fundamental electric-magnetic field propagating in the TE(10) mode concentrated in the gap between the ridges. This paper reports experimental demonstration of fie...