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The resonance wavelengths of optical Möbius strip microcavities can be continuously tuned via geometric phase manipulation by changing the thickness-to-width ratio of the strip.
Robotic and other devices often demand ever more compact and sophisticated sensors. This Review assesses the opportunities for metasurfaces to provide optical functionality solutions for such applications.
Nonlocal effects—in which the optical response of a system at a given spatial point depends on the field in the surrounding space—are reviewed in the context of metasurfaces and flat optics. Nonlocal flat optics may be useful for controlling light in ultra-thin platforms.
Recent developments in reconfigurable metasurfaces are reviewed with a focus on case studies that are promising for commercialization and associated challenges.
Using two different designs of superconductor-based detectors, two independent research groups report photon number detection for light pulses with up to 100 photons.
Superconducting nanowire single-photon detectors offer outstanding performance, but the development of large-format imaging arrays is challenging. A new approach based on sectioning a single nanowire enables an eightfold improvement of the spatial resolution and the realization of a 1,024-pixel imager.
The free-carrier dispersion effect with photo-excited free carriers provides all-optical control of the resonance of photonic crystal microcavities. Using this technique, a spatial light modulator comprising optically addressed cavity arrays has been developed for high-efficiency, high-bandwidth spatiotemporal modulation of light.
Experimental confirmation that the Gouy phase can modify the photonic de Broglie wavelength opens up many exciting directions in metrology using quantum systems with higher-order Gaussian modes.
Suppression of exciton–vibration coupling yields organic light-emitting diodes that emit at 1,000 nm in the NIR-II spectral region, which is important for biological imaging.
Ultrasound-induced gas bubbles in tissue can temporarily minimize optical scattering, enabling laser light to be focused at greater depth for higher-resolution imaging.
Several research groups have now succeeded in achieving lasing in free-electron lasers (FELs) driven by compact plasma wakefield accelerators. In the future, the approach may ultimately lead to a new breed of much smaller, more affordable FELs.
The use of on-chip nonlinear waveguides that can convert 1.5-μm wavelength signals into the 2-μm region brings new opportunities for expanding the bandwidth of optical communications.