Helmholtz-Structured Two-Dimensional Super-Diffraction Meta-Lens

Two-dimensional sonic crystals with Helmholtz resonators.

We present a type of sonic crystal composed with an array of two-dimensional Helmholtz resonators, which in the long-wave regime have both a high relative acoustic refractive index n and at the same time, a small acoustic impedance Z mismatch with air for airborne sound. We analyze the n and Z of such sonic crystals by finite-difference time-domain simulations, and by mapping our results to a c...

Two-dimensional X-ray powder diffraction

Diffraction properties of two-dimensional photonic crystals

We show that the envelope of the diffraction efficiency of a two-dimensional photonic crystal can exhibit spectral regions of very small diffraction efficiency (,5310), while in other regions, the diffraction efficiency is near unity. The experimental results on higher bands of hexagonal, silicon-based photonic crystals agree well with corresponding numerical calculations and highlight the prom...

Diffraction effects in single- and two-laser photothermal lens spectroscopy.

A simple method for calculating the effects of optical geometry on photothermal lens signals is shown. This method is based on calculating cumulative electric-field phase shifts produced by a series of Gaussian refractive-index perturbations produced by the photothermal effect. Theoretical results are found for both pulsed-laser and continuous Gaussian laser excitation sources and both single- ...

Spectrum of Two-Dimensional (Super)Gravity∗

We review the BRST analysis of the system of a (super)conformal matter coupled to 2D (super)gravity. The spectrum and its operator realization are reported. In particular, the operators associated with the states of nonzero ghost number are given. We also discuss the ground ring structure of the super-Liouville coupled to ĉ = 1 matter. In appendices, hermiticities, states for c < 1 conformal ma...