相关论文: High-frequency Limits for 3D-Printed Gradient-inde…
We present the design and characterization of waveguide grating devices that couple visible-wavelength light at $\lambda=674$ nm from single-mode, high index-contrast dielectric waveguides to free-space beams forming micron-scale…
The sky-averaged brightness temperature of the 21cm line from neutral hydrogen provides a sensitive probe of the thermal state of the intergalactic medium, particularly before and during Cosmic Dawn and the Epoch of Reionisation. This…
In the framework of the Compact Light XLS project, a short ultra-high gradient linearizer working on the third harmonic of the main LINAC frequency is requested. Increasing gradients and reducing dimensions are requirements for XLS and all…
Lenses are typically based on refractive index profiles derived from the geometric approximation of high-frequency waves, yet the critical issue of impedance mismatch is often neglected. Mismatched devices suffer from unwanted reflections…
As telescopes get larger, the size of a seeing-limited spectrograph for a given resolving power becomes larger also, and for ELTs the size will be so great that high resolution instruments of simple design will be infeasible. Solutions…
An experimental demonstration of directivities exceeding the fundamental Kildal limit, a phenomenon called superdirectivity, is provided for spherical high-index dielectric antennas with an electric dipole excitation. A directivity factor…
There is an ever increasing interest in the development of plasmonic 2D nanomaterials, with widespread applications in optoelectronics, high resolution microscopy, imaging and sensing, among others. With the current ability of ultrathin…
We use optical transient-grating spectroscopy to measure spin diffusion of optically oriented electrons in bulk, semi-insulating GaAs(100). Trapping and recombination do not quickly deplete the photoexcited population. The spin diffusion…
In this paper, a novel gradient index (GRIN) acoustic metamaterial is proposed based on the concept of optical modified generalized Luneburg lens (MGLL). With the MGLL, double-foci and high energy density between the two foci can be…
We design an all-dielectric L\"uneburg lens as an adiabatic space-variant lattice explicitly accounting for finite film thickness. We describe an all-analytical approach to compensate for the finite height of subwavelength dielectric…
In this work, a method is presented to maximize the obtained gain from millimeter-wave (mm-wave) lens antennas using phase center analysis. Commonly, for designing a lens antenna, the lens is positioned just on top of the antenna element…
Interferometric gravitational wave antennas are based on Michelson interferometers whose sensitivity to small differential length changes has been enhanced by adding multiple coupled optical resonators. The use of optical cavities is…
In this paper, a novel gradient index (GRIN) structural lens based on the concept of generalized Luneburg lens (GLL) is proposed. This lens allows for the realization of double foci and localization of energy flow between the two focal…
Ultrathin metasurfaces have recently emerged as promising materials to enable novel, flat optical components and surface-confined, miniature photonic devices. However, experimental realization of high-performance metasurfaces at visible…
The Giant Radio Array for Neutrino Detection (GRAND) is an envisioned large-scale radio array designed to detect ultra-high-energy cosmic rays (UHECRs, $E > 100$ PeV) and neutrinos. Employing cost-effective antennas distributed across vast…
We describe an ongoing experiment to search for the meta-galactic Lyman-continuum background at z~2-3. We are obtaining one of the deepest optical spectra ever, using LRIS/Keck-II to search for the fluorescent Ly-alpha emission from…
Luneburg lens is a symmetric gradient-index lens with a refractive index that increases from the outer surface to the center in a radial manner. It has the ability to focus and collimate waves, which makes it useful for energy harvesting,…
The High Luminosity upgrade of the CERN Large Hadron Collider will be able to reach a peak instantaneous luminosity of 5E34/cm2 s. The innermost detectors of the CMS and ATLAS experiments will have to cope with unprecedented requirements on…
We present a systematic study of high-contrast dielectric gratings operating as broadband quarter-wave plates in the terahertz range. Using higher-order effective medium theory, we identify an achromatic operating regime characterized by a…
A method for the agile generation of the optical frequencies required for laser cooling and atom interferometry of rubidium is demonstrated. It relies on fiber Bragg grating technology to filter the output of an electro-optic modulator and…