No abstract

Optical computing holds significant promise of information processing with ultrahigh speed and low power consumption. Recent developments in nanophotonic structures have generated renewed interests due to the prospects of performing analog optical computing with compact devices. As one prominent example, spatial differentiation has been demonstrated with nanophotonic structures and directly applied for edge detection in image processing. However, broadband isotropic two-dimensional differentiation, which is required in most imaging processing applications, has not been experimentally demonstrated yet. Here, we establish a connection between two-dimensional optical spatial differentiation and a nontrivial topological charge in the optical transfer function. Based on this connection, we experimentally demonstrate an isotropic two-dimensional differentiation with a broad spectral bandwidth, by using the simplest photonic device, i.e. a single unpatterned interface. Our work indicates that exploiting concepts from topological photonics can lead to new opportunities in optical computing.

The logic underlying inclusive STEM high schools (ISHSs) posits that requiring all students to take advanced college preparatory STEM courses while providing student-centered, reform-oriented instruction, ample student supports, and real-world STEM experiences and role models will prepare and inspire students admitted on the basis of STEM interest rather than prior achievement for postsecondary STEM. This study tests that logic model by comparing the high school experiences and achievement of students in ISHSs and comparison schools in North Carolina. After identifying ISHS and non-STEM comparison high schools serving students who were similar in terms of socioeconomic status and academic achievement prior to high school entry, we employed propensity-score weighting and HLM modeling to estimate the impact of attending an ISHS on a set of outcome measures obtained from student surveys and from the state's longitudinal student data system. Analyses of student survey data found that attending an ISHS raises the likelihood that a student will complete pre-calculus or calculus and chemistry in high school, leads to increased involvement in STEM extracurricular and out-of-class activities, and enhances interest in science careers and aspirations to earn a master's or higher degree. Analyses of student outcome data from state administrative records revealed a positive impact of inclusive STEM high school attendance on grade point average (GPA) but not on ACT scores.

There has been substantial interest in miniaturizing optical systems by flat optics. However, one essential optical component, free space, fundamentally cannot be substituted with conventional local flat optics with space-dependent transfer functions, since the transfer function of free space is momentum-dependent instead. Overcoming this difficulty is important to achieve the utmost miniaturization of optical systems. In this work, we show that free space can be substituted with nonlocal flat optics operating directly in the momentum domain. We derive the general criteria for an optical device to replace free space and provide two concrete designs of photonic crystal slab devices. Such devices can substitute much thicker free space. Our work paves the way for the utmost miniaturization of optical systems using a combination of local and nonlocal flat optics.