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Photograph of a number of electromechanically pumped optical isolators on an aluminium nitride chip. These magnet-free isolators use sound waves to break time-reversal symmetry for light propagation. The devices are fabricated by electron-beam photolithography and the isolation band for each device can be lithographically defined. The isolators are designed for operation near 1,550 nm with a bandwidth exceeding 1 GHz.
Metasurfaces can in principle provide a versatile platform for optical functionalities, but in practice designing and fabricating them to specifications can be difficult. Now, the realization of metasurfaces with engineered disorder allows for versatile optical components that combine the best features of periodic and random systems.
Implementing non-reciprocal elements with a bandwidth comparable to optical frequencies is a challenge in integrated photonics. Now, a phonon pump has been used to achieve optical non-reciprocity over a large bandwidth.
Irradiating arrays of metal nanowires with intense femtosecond laser pulses produces high-brightness picosecond X-ray pulses. By specifically tailoring the plasma properties, up to 20% conversion efficiency of optical light into X-rays can be achieved.
The ability to switch fluorophores on and off is key to performing super-resolution nanoscopy. To date, all switching schemes have been based on an incoherent response to the laser field. Now, a nanoscope that uses on–off coherent switching of quantum dots has been demonstrated.
A spatial resolution of 30 nm (=λ/31) exceeding the diffraction limit is achieved by super-resolution fluorescence microscopy. The nanoscopic imaging scheme can be applied to coherent quantum-mechanical systems such as quantum dots, as well as colour centres.
Using designer-disordered metasurfaces, optical input–output characteristics, which are typically difficult to obtain, can be known a priori. The approach is used for wavefront shaping, high-numerical-aperture focusing and fluorescence imaging.
Multijunctions have long been used to enhance photovoltaic solar cell efficiency. Here, a large-area tandem luminescent solar concentrator is demonstrated using two types of quantum dot with low reabsorption.
Using an ultrafast, time-stretched frequency comb laser operating with repetition rates from 7.6 MHz to 18.9 MHz, a rapid and large-volumetric-field optical coherence tomography at an imaging rate of up to 7.5 volumes per second is demonstrated.