Low-Power Laser Sailing for Fast-Transit Space Flight.

Space exploration is of paramount importance to advancing fundamental science and the global economy. However, today's space missions are limited by existing propulsion technologies. Here, we examine the use of laser-driven light sailing for agile Earth orbital maneuvering and for fast-transit exploration of the solar system and interstellar medium. We show that laser propulsion becomes practical at laser powers ≥100 kW and laser array sizes ∼1 m, which are feasible in the near term. Our analysis indicates that lightweight (1-100 g) wafer-scale (∼10 cm) spacecraft may be propelled by lasers to orbits that are beyond the reach of current systems. We discuss material requirements and photonic designs and introduce new figures of merit. We show that lightsails made of silicon nitride and boron nitride are particularly well suited for the discussed applications. Our architecture may pave the way to ubiquitous Earth orbital networks and fast-transit low-cost missions across the solar system.

Origin and manipulation of band gaps in three-dimensional dielectric helix structures.

In this study, we present a comprehensive analysis to examine the origin of circular polarization stop bands in a dielectric helix structure. We show that band gaps in a helix structure may result from Bragg resonance or non-Bragg mechanism. The two types of gaps exhibit distinct optical properties and display an opposite dependence with respect to structural periodicity. The interplay of gaps not only gives rise to various operation scenarios, but results in pronounced modifications to dispersion characteristics that lead to abnormal propagation properties of circularly polarized waves. Our findings reveal versatile behaviors of circularly polarized light interacted with a three-dimensional helix medium, which can be of great importance for the design and implementation of circular polarization-dependent devices and applications.