Dispersion engineering of metamaterials is critical yet not fully released in applications where broadband and multispectral responses are desirable. Here we propose a strategy to circumvent the bandwidth limitation of metamaterials by implementing two-dimensional dispersion engineering in the meta-atoms. Lorentzian resonances are exploited as building blocks in both dimensions of the dedicatedly designed meta-atoms to construct the expected dispersion. We validated this strategy by designing and fabricating an anisotropic metamirror, which can accomplish achromatic polarization transformation in 4-octave bandwidth (two times of previous broadband converters). This work not only paves the way for broadband metamaterials design but also inspire potential applications of dispersion management in nano-photonics. Since it was firstly illustrated by the pronounced prism experiment of Isaac Newton, the roles of chromatic dispersion in the interactions between electromagnetic wave and matter are extensively explored. It has been widely accepted that dispersion management is crucial in constructing spectrometers 1 , superprisms 2 , achromatic lens systems 3 , analog and digital optical communication system 4 . Proper dispersion contributes not only to the dense wavelength division multiplexing (DWDM) system 5 , but also the generation of soliton waves 6 . Dispersion of natural materials is determined by the electronic and molecular energy levels, with limited tunability. In the last decades, metamaterial has emerged as revolutionary material offering unprecedented superiority for dispersion engineering, while its electromagnetic property is exclusively decided by the specific geometry and arrangement of artificial meta-atoms [7][8][9][10][11] . Nevertheless, the difficulties in manufacture impede the further development of bulk metamaterials. As two-dimensional metamaterials, metasurfaces relax the fabrication requirement and meanwhile provide plenty of exotic properties such as phase discontinuity and abnormal deflection [12][13][14] . Especially, the ability to manipulate the polarization of electromagnetic waves is sought-after for numerous applications 15 . The past decade has witnessed the flourish of metasurface as polarization transformers owing to the miniaturized dimension and higher efficiency compared to traditional wave plates [16][17][18][19][20][21] . Theoretical investigations elucidate that the maximal conversion efficiency through a single metasurface can increase to 100% after introducing a reflective plane 22 . However, the highly resonant nature of meta-atoms that force the electromagnetic waves undergo a phase change ultimately causes a small bandwidth around their design frequency, as a result of the general Kramers-Kronig relations 23 . A nascent strategy to circumvent the bandwidth limitation of polarization converters is dispersion management 15,24 . This concept was also widely exploited in perfect absorbers [25][26][27][28][29] and band-pass filters 30 . Strikingly, the absorption bandwidth ca...

As an emerging topic, photonic-assisted microwave measurements with distinct features such as wide frequency coverage, large instantaneous bandwidth, low frequencydependent loss, and immunity to electromagnetic interference, have been extensively studied recently. In this article, we provide a comprehensive overview of the latest advances in photonic microwave measurements, including microwave spectrum analysis, instantaneous frequency measurement, microwave channelization, Doppler frequency-shift measurement, angle-of-arrival detection, time-frequency analysis, compressive sensing, and phase-noise measurement. A photonic microwave radar, as a functional measurement system, is also reviewed. The performance of the photonic measurement solutions is evaluated and compared with the electronic solutions. Future prospects using photonic integrated circuits and software-defined architectures to further improve the measurement performance are also discussed.

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The intestinal protozoan pathogen Entamoeba histolytica lacks mitochondria and derives energy from the fermentation of glucose to ethanol with pyruvate, acetyl enzyme Co-A, and acetaldehyde as intermediates. A key enzyme in this pathway may be the 97-kDa bifunctional E. histolytica alcohol dehydrogenase 2 (EhADH2), which possesses both alcohol dehydrogenase (ADH) and acetaldehyde dehydrogenase activity (ALDH). EhADH2 appears to be a fusion protein, with separate N-terminal ALDH and C-terminal ADH domains. Here, we demonstrate that EhADH2 expression is required for E. histolytica growth and survival. We find that a mutant EhADH2 enzyme containing the C-terminal 453 amino acids of EhADH2 has ADH activity but lacks ALDH activity. However, a mutant consisting of the N-terminal half of EhADH2 possessed no ADH or ALDH activity. Alteration of a single histidine to arginine in the putative active site of the ADH domain eliminates both ADH and ALDH activity, and this mutant EhADH2 can serve as a dominant negative, eliminating both ADH and ALDH activity when co-expressed with wild-type EhADH2 in Escherichia coli. These data indicate that EhADH2 enzyme is required for E. histolytica growth and survival and that the C-terminal ADH domain of the enzyme functions as a separate entity. However, ALDH activity requires residues in both the N-and C-terminal halves of the molecule.The anaerobic intestinal protozoan parasite Entamoeba histolytica converts pyruvate to ethanol in its fermentation pathway (1). The last two steps of this pathway are the conversion of acetyl-CoA to acetaldehyde followed by the reduction of acetaldehyde to ethanol (1). E. histolytica possesses at least three enzymes with alcohol dehydrogenase (ADH) 1 activity: a NADP-dependent ADH (EhADH1); a 97-kDa NAD(ϩ)-dependent and Fe 2ϩ -dependent bifunctional enzyme with both ADH and acetaldehyde dehydrogenase (ALDH) activities (EhADH2, also known as EhADHE); and a 43-kDa NADP-dependent ADH with some sequence homology to class III microbial alcohol dehydrogenases (EhADH3) (2-5). There are at least two enzymes with ALDH activity, the EhADH2 enzyme and a NADPdependent ALDH, EhALDH1 (2, 5, 6). Given the presence of multiple ADH and ALDH enzymes in E. histolytica, an important question is whether any of these enzymes are essential for E. histolytica growth and survival and thus potential targets for anti-amebic therapy.The EhADH2 enzyme is part of a newly described family of multifunctional enzymes found in Gram-negative and Grampositive bacteria and the intestinal protozoan parasite Giardia lamblia (2, 7-12). EhADH2 and other members of the family appear to be composed of separate C-terminal ADH and Nterminal ALDH domains linked together to create a fusion enzyme (8). The EhADH2 enzyme utilizes NAD and Fe 2ϩ as co-factors and does not demonstrate homology with the zincdependent ADH enzymes (13). Regions of EhADH2 that could be involved in iron binding and NAD binding have been identified, but a requirement for specific residues in enzymatic activity has not been demo...